The Luciolinae

Contents

Ventrite 7

     MPP

     PLP

     other

Light organs

     LO bipartite

     LO anterior emargination

     LO posterior emargination

     Loss of LO

     Origin

     Dorsal face

Tergite 8

Functional interpretations

Ventrite 7 modifications

Ventrite 7 shows modifications of great importance in taxonomy.  This section is expanded from Ballantyne 1987, Ballantyne 1993 and Ballantyne & Lambkin 2013. Ballantyne and Lambkin (2013) Tables 12, 13 overviewed abdominal characteristics of species with a trisinuate ventrite 7 in males and is accessible on this website.

Median posterior projection of ventrite 7 - MPP

The median part of the posterior margin of ventrite 7 may be prolonged posteriorly in Atyphella (Ballantyne & Lambkin 2009 Figs 10, 79, 83), scarcely prolonged and emarginate in Pyrophanes, and Pteroptyx; considerably prolonged, emarginate, and terminating in paired dorsally curving hooks, seen in the least developed form in Colophotia brevis, Australoluciola nigra and Aus. flavicollis, and in its most extreme development in certain Colophotia (Ballantyne & Lambkin 2009 Figs 10, 79, 83; Ballantyne et al. 2019 figs 211, 212, 215, 216, 217); a slender elongate prolongation in which there is no pronounced dorsal curvature of the apex, in Pygatyphella  (Ballantyne & Lambkin 2009 Figs 10, 79, 83) or a similar prolongation which curves dorsally at its apex, engulfing tergite 8, in certain Pygoluciola (Ballantyne & Lambkin 2009 Figs 10, 79, 83).

McDermott  (1964) described Luciola hamulata (assigned to Pygoluciola by Ballantyne, 1968) with extended hooks on the last abdominal ventrite. The ventrite 7 prolongation of this species is not apically emarginate and curves dorsally (Ballantyne & Lambkin 2009 Figs 10, 79, 83). The similar projection of Pygoluciola wittmeri is however widely bifurcate, and ensheathes laterally the prolonged and downturned apex of tergite 8 (Ballantyne & Lambkin 2006 figures on page 26). McDermott also observed that the prolongations of the midposterior margin of ventrite 7 of Luciola ovalis, L. humilis and L. hamulata [the generic names of these species have changed and they are now respectively Asymmetricata, Australoluciola and Pygoluciola] "are strongly suggestive of the cleft last ventral segment and appended hooks found in Colophotia" and "undoubtedly part of the male genitalia." They are developments of ventrite 7 only, not of the aedeagus proper. Only the median projection of ventrite 7 of L. humilis (now Aus. nigra) (Ballantyne & Lambkin 2009 Figs 10, 79, 83) is apically gently emarginate, terminating in small dorsally inclined hooks. The similar projection of L. ovalis (now Asymmetricata ovalis) is apically entire (Ballantyne & Lambkin 2009 Figs 10, 79, 83).

Posterolateral corners of ventrite 7 - PLP

The posterolateral corners or projections of ventrite 7 are usually referred to in Ballantyne’s descriptions in an abbreviated form as PLP; they are completely absent, or scarcely developed, apically rounded, and not at all prolonged in Atyphella, Missimia, Pygoluciola, some Pteroptyx and some Australoluciola (e.g. Ballantyne & Lambkin 2009 Figs 10, 79, 83); moderately developed as rounded projections in Pyrophanes, some Pteroptyx (e.g. Ballantyne & Lambkin 2009 Figs 10, 79, 83); most extremely developed in some Colophotia (Ballantyne & Lambkin 2009 Figs 98-100; Ballantyne et al. 2019 figs 211-215), Pteroptyx macdermotti (Ballantyne, 2001; Jusoh et al. 2018 figs 97-99, 101, 102) and certain Pteroptyx (Ballantyne & Lambkin 2009 Figs 10, 79, 83; Jusoh et al. 2018 figs 12, 17-20, 31, 32, 41, 42, 44, 45, 63, 83, 84). 

In Pteroptyxs. str. the bipartite light organ of ventrite 7 occurs in those species in which the posterolateral projections of ventrite 7 are prolonged (with the exceptions of P. valida, P. maipo and P. tener; Ballantyne 2001; Ballantyne et al. 2011; see figures in Jusoh et al. 2018). In Medeopteryx spp. where the light organ is undivided in ventrite 7, the posterolateral projections do not extend beyond the apex of the median posterior projection (see Ballantyne & McLean 1970, Ballantyne 1987; Ballantyne & Lambkin 2009 figs 96, 97). In Pteroptyx spp. which have a bipartite light organ in ventrite 7 there is variation in the development of these processes e.g. they may be produced posteriorly, often narrowed, and separated by concave emarginations from the median posterior projection as in Pteroptyx malaccae (Ballantyne 2001 Figs 19-24; Jusoh et al. 2018  figs 120, 121, 124, 125); angulate but not produced posteriorly and not separated from the median posterior projection by any emargination as in Pteroptyx tener (Ballantyne & Menayah 2000 Fig. 1; Jusoh et al. figs162, 163); rounded, scarcely produced posteriorly, with scarce emarginations in P. valida (Ballantyne 2001 Fig. 43; Jusoh et al. figs 205-208). Their most extreme development, in any bent winged firefly, occurs in Pteroptyx macdermotti, where the bipartite light organ is considerably reduced (Ballantyne 2001 Fig. 37; Jusoh et al 2018 figs 97, 101). 

The bipartite light organ in Pteroptyx, Medeopteryx and Trisinuata results at least in part from muscle attachment in the median area of the dorsal face of ventrite 7.

Other modifications of ventrite 7

In most Pygatyphella at least the posterior third of ventrite 7 is expanded and sometimes inclined dorsally. This is most pronounced in Pygatyphella undulata where there is no posterior median projection of ventrite 7 as such (Ballantyne & Lambkin 2009 Figs 10, 79, 83). Muscles are visible through the cuticle in this area in dried pinned specimens of most Pygatyphella (Ballantyne & Lambkin 2009 Figs 10, 79, 83). They meet in the median line and contract in a fan like arrangement to attach laterally to the underside of tergite 7 which like tergite 8 in this genus is heavily sclerotised.

Certain Pteroptyx have a "dimple" (a depression) developed on the ventral face of ventrite 7 (Ballantyne & McLean 1970 Fig. 7; Ballantyne 1987 Fig. 2i) anterior to the arched area of the surface of the median posterior projection, the "hump". This may be a consequence of the torsion of the longitudinal muscles attaching anterior to the projection (I was without inspiration the day I named these parts!!). 

Only in Pyrophanes Pteroptyx macdermotti and Pteroptyx gombakia is there development of slender incurving lobes arising from the midposterior margin of ventrite 7 (Ballantyne 2001 Fig 37; Ballantyne & Lambkin 2009 Figs 106, 107; Jusoh et al. 2018 figs 92-94, 98, 101, 102), between the median posterior projection and the posterolateral corners. They are not hairy lobes in gombakia. 

There is a median carina in ventrite 7 of some Colophotia investigated by Ballantyne & Lambkin 2009 Figs 10, 79, 83. McDermott (1962) considered it a "triangular plate projecting through the slot". There is no slot in the region of the carina; the light organ of ventrite 7 is bipartite and the area around the carina may be a little depressed and thus appear "slot-like". McDermott considered his figure 23b of the lateral aspect of the end of the abdomen showed the "projecting aedeagus" and the "triangular plate". The latter is the median carina. The aedeagus is not visible in this unlabelled figure and McDermott's reference is either to the bifurcate median projection of ventrite 7, with its well developed and dorsally curving hooks, or to the posterolateral projections of that ventrite. 

McDermott (1964) described the "trilobed" structure of Pyrophanes abdomen. He was referring to the abdomen of Pteroptyx macdermotti (named subsequently by McLean in Ballantyne and McLean, 1970) which he is known to have examined at this time, and which shows similarities with Pyrophanes (McDermott, pers. comm.). His comment on the trilobed nature of ventrite 7 is more appropriately applied to Pteroptyx.

Extent of light organ

Light organs are beneath the transparent cuticle of ventrites 6 and 7 and visible through them as cream or white areas. The term "light organ" is applied to the entire pale area in either ventrite 6 or 7. The light organ usually occupies ventrite 6 completely although it may be retracted narrowly along lateral and posterior margins (it is restricted to anterolateral plaques in Luciola hypocrita and Atyphella scabra  see Ballantyne & Lambkin 2009 figs 178, 179). The light organ occupies ventrite 7 completely except for a relatively narrow posterior margin in many species of the genera Luciola and Atyphella and Medeopteryx); it is restricted to the anterior median area of the ventrite in Pygoluciola spp. and Aquatica spp. (Ballantyne & Lambkin 2006 Figs18, 19, 23) where in Pygoluciola the lateral margins of ventrite 7 are free of light organ material; it is restricted to the anterior half or less in Missimia (Ballantyne & Lambkin 2009 Fig. 253), and some Pygatyphella (Ballantyne & Lambkin 2009 e.g. Figs 24, 305-308, 320, 321, 342, 387), where it may be emarginate across the posterior margin (Ballantyne & Lambkin 2009 Figs 24, 320, 321, 453, 454); bipartite in Pyrophanes, Colophotia, all oriental Pteroptyx, Trisinuata, a few Atyphella and one Pygatyphella. 

McDermott (1964) indicated that while 3 luminous segments had been reported for some species he had not seen one with more than two. McLean's histological studies of light organs of certain Lampyridae (Ballantyne & McLean, 1970) indicated that where abdominal ventrites 5, 6 and 7 were white, the light organs were confined to ventrites 6 and 7.

LO reduction in V7. Bipartite LO.

Ballantyne (1987b) considered the bipartite LO in V7 had arisen because of insertion of median longitudinal muscles between LO halves. While this could be the correct explanation in certain Pteroptyx and Trisinuata the situation in other genera appears more complicated. Species of Medeopteryx with entire LOs in V7 may have cuticular strips passing over the dorsal surface of the LOs and connecting anteriorly with longitudinal abdominal muscles (Ballantyne & Lambkin 2009 Fig. 97). In Med. clipeata the anterior area of the LO is missing and occupied by muscle attachments, and this situation might represent an intermediate stage between the entire and bipartite LOs in V7 at least in Medeopteryx species. However in Pteroptyx testacea the LO halves are virtually contiguous in the median line with no obvious muscle attachments causing their separation (Jusoh et al. 2018 Fig 187). In Colophotia spp. a median carina is developed on the ventral face of V7 between LO halves. Pteroptyx maipo has bipartite LOs in V7, the inner margins of which approach closely in the posterior half of V7, while being well separated in the anterior half (Ballantyne et al. 2011 Fig. 33 shows scarce separation between LO halves while Fig. 31 of P. valida shows separation well). 

LO in ventrite 7 with anterior emargination. 

The light organ may be emarginate across its anterior margin as in Asymmetricata circumdata and species of Sclerotia (Ballantyne et al. 2019 Figs 11, 145-147). The reason for the emargination has not been investigated in the former, but it may be the first step towards the development of a bipartite light organ. In Sclerotia muscles from the three sclerites surrounding the aedeagal sheath attach in part on the dorsal face of ventrite 7 and account for the emargination. 

Asymmetricata circumdata has the LO entire in V7 with a small triangular emargination along the middle of the anterior margin. This coincides with a longitudinal groove (developed in some but not all specimens) which runs along the anterior half of the ventral face of V7, but there is no explanation for its function. Ballantyne & Lambkin (2009) surmised that As. circumdata (with entire LO in V7) and As. ovalis (with bipartite LO in V7) could be the same species with a series of intermediate steps in LO reduction. No such specimens have been discovered  (see Ballantyne et al. 2019 Figs 145-147). 

Sclerotia species (Ballantyne & Lambkin 2009 Fig. 5 Node 62; Ballantyne et al. 2016 and figures therein)) have a set of three sclerites surrounding the aedeagal sheath. Muscles from the largest (ventral) sclerite attach at least in part on the dorsal face of V7 and account for the emargination of the LO in this area. Medeopteryx clipeata has a fairly wide anterior emargination of an otherwise entire LO in V7 and muscle impressions are clearly visible in the area.

LO in ventrite 7 with posterior emargination.

In Pygatyphella spp. the posterior margin of the entire LO in V7 is often emarginated, sometimes deeply, and the emargination allows for muscle attachment (Ballantyne & Lambkin 2009  Figs 315, 320, 321). 

Loss of LO 

There are circumstances where the LO may be being lost rather than being reduced for functional purposes of muscle attachment as above. Here it would be assumed the species come to rely on other, possibly olfactory, clues. The New Guinean Atyphella scabra Olivier has very reduced LOs occurring as lateral plaques in both V6 and 7 (Ballantyne & Lambkin 2009 figs 178, 179), but the female is unknown. Males however have very short antennae. Luciola hypocrita has no LO in V7 and anterolateral LO plaques in V6 only (Deheyn & Ballantyne 2008); the female is flightless. L. oculofissa is the only Luciolinae species known thus far where there is no LO. Both hypocrita and oculofissa have eye emarginations, huge in the latter species (Ballantyne & Lambkin 2013 Figs 120-122). The non-lucioline Rhagophthalmus spp. males lack a LO but have huge emarginated eyes, and short antennae, and their females are brightly luminous and larviform (Ho et al. 2012).

Origin of LOs in V7. 

Ballantyne et al. (2011) indicated that the larval and adult LOs may not be homologous, since studies on light production by late instar larvae and pupae indicate the LOs are broken down and reassembled (larvae have a LO in abdominal segment 8, while in adult males the LO is in segments 6 and 7, and in females only in segment 6). Yiu’s (2011) study on the light configurations of several Luciolinae larvae and adults illustrate larval LO remnants in V8 in the female which disappear as the adult LOs in V6 are developed.

The dorsal face of ventrite 7

Developments of the dorsal face of ventrite 7 have been studied mainly in Medeopteryx which have an entire light organ in ventrite 7. Species studied possess cuticularised strap-like pieces which extend anteriorly across the dorsal face of the light organ (Ballantyne 1987 Figs 4, 5, 7, 10, 11, 12, 13; Ballantyne & Lambkin 2009 Fig. 97). Muscles attaching anteriorly to these insert in part on the aedeagal sheath and partly on the anterior margin of ventrite 7. Gentle tugging on these straps with fine forceps will cause the median posterior projection of ventrite 7 to arch dorsally. In contrast species in which the light organ is bipartite in ventrite 7 appear to have a slightly different method of arching the median posterior area of ventrite 7, in that muscles insert at least in part on the median area of ventrite 7 between light organ halves.

Development of tergite 8

Prolongation of tergite 8 medianly as a slender elongate projection occurs in Pygoluciola(Ballantyne & Lambkin 2006 Figs 18, 19, 20, 22, 23, 25, 26). In Pygatyphella spp. tergite 8 may narrow posteriorly (e.g. Ballantyne & Lambkin 2009 Figs 311, 312, 314, 322, 360, 361, 410); the apex of tergite 8 is ventrally curved in Pygat. undulata where it envelops the tip of ventrite 7 (Ballantyne & Lambkin 2009 Figs 452-454), and in Pygoluciola spp. (e.g. Pygoluciola hamulata Ballantyne & Lambkin 2009 Fig. 60) and is bifurcate in Pygoluciola wittmeri.

In Pteroptyx and Medeopteryx the median posterior margin of tergite 8 is emarginate, a midventral longitudinal trough houses the aedeagal sheath, and the reflexed lateral margins of tergite 8 (ridges) form the lateral borders of this trough. The median trough and lateral ridges are better developed in New Guinean Medeopteryx, where projections (flanges) of varying shapes arise from the anteromedial angles of the downturned lateral margins and incline anteriorly (Ballantyne 1987 Fig. 14 h, k). The shape of the flanges is of taxonomic importance. Tergite 8 of most oriental Pteroptyx lacks these flanges (Ballantyne 1987 Fig. 14 d, l) and the downturned margins may be more obviously developed across the posterior margin of tergite 8. Lateral protuberances of the aedeagal sheath tergite in oriental Pteroptyx might be generally incompatible with flanges on tergite 8. 

Modifications of tergite 8 in other genera are seen. Many of these may well be shown to be more directly related to muscle attachments as more specimens become available for study. In Pyrophanes the lateral portions of the ventral surface of tergite 8 (to the sides of the median trough) are further depressed and bear spines and hairs. In a few pinned Pyrophanes the posterior margin of ventrite 7 between but not including the posterolateral projections, may be inclined dorsally at right angles to the median line, and in this position the incurving projections of this margin appear to make contact with the spines and hairs of tergite 8.  The ventral face of tergite 8 is medially grooved in many Luciola, Pyrophanes and Colophotia, and houses the aedeagal sheath. The anterior margin of tergite 8 is bifurcate and often prolonged anteriorly beneath tergite 7. In Colophotia these prolongations are very long and coincide with the extra long aedeagal sheath. Only in this genus are the anterolateral corners of tergite 7 slightly prolonged as well. Tergite 8 of Asymmetricata species is strongly asymmetrical and emarginate on its left side suggesting the aedeagus can only be extracted in this direction (no obvious asymmetry exists in the aedeagal sheath however). 

(This section extracted with some modifications from Ballantyne 1987, Ballantyne 1992 and Ballantyne & Lambkin 2013)

The Luciolinae have lost any external manifestations of ventrite 8 and it is my contention that the loss of this ventrite has predisposed the terminal Luciolinae abdomen to many of the modifications we see there. It appears that the architecture of the abdomen is related to the mechanics of copulation and the mechanisms of the associated musculature, and because ventrite 8 is no longer a surface for muscle attachment then other areas must be developed to provide that area, especially as it relates to the light organ area. Many of the external morphological manifestations of the abdomen are not of copulatory significance in themselves, but are thus external manifestations of the need for increased surface area for muscle attachment. Included are the longitudinal ventral muscles that achieve abdominal flexion, the intersegmental muscles attaching ventrite 7 to sternite 9 and tergite 8 to tergite 9, and the dorsoventral muscles from tergite 7 to ventrite 7. A surface area for attachment is required and a form of reinforcing against muscle pull. Mechanical modifications (those not obviously directly related to actual muscle insertions) may follow as a consequence of muscle development in other areas.

Wing et al. (1983) described a copulation clamp in Pteroptyx valida where the deflexed elytral apices of the male press down on the enlarged median posterior projection of ventrite 7 and, when the coupled pair is tail to tail, wedges them together. Discovery of this copulation clamp led Ballantyne to a more detailed anatomical study of many Pteroptyx species which revealed modifications that could be directly related to their use in a clamp situation. 

A bipartite light organ may result from insertion of muscles in the median area of ventrite 7. In Pteroptyx muscles attaching on the intersegmental membrane anterior to the median posterior projection of ventrite 7 insert on the median dorsal face of ventrite 7. Contraction of these muscles, which insert also in part on sternite 9, result in some dorsal arching of the median projection. In Medeopteryx with light organ in ventrite 7 entire a similar group of muscles insert more anteriorly in the intersegmental area between ventrites 6 and 7. Additional cuticularisation of the intersegmental membrane occurs in the form of cuticular strips. Tugging on these strips with forceps in an anterior direction causes the median posterior projection of ventrite 7 to arch as it might in a clamp situation (manipulation performed on wet alcohol preserved specimens only). Medeopteryx clipeata has an entire light organ which is emarginate along its anterior margin (similar to the situation seen in Sclerotia substriata).

The bipartite light organ, the reduction of the light organ to the anterior half or less of ventrite 7, and the reduction of light organ area in the anterior median area only of ventrite 7 all allow for muscle attachment on that ventrite. 

Modifications relating directly to muscle attachments are seen in other genera. Several Australian Australoluciola species which have light organs in ventrite 7 entire but reduced to the anteromedian position of ventrite 7 also have a posterior prolongation of the median posterior area of ventrite 7.  Many muscles visible through the cuticle in dried pinned specimens of Pygatyphella species insert on the posterior part of this prolongation, which may have been developed as a reinforcing rod to counter muscle pull, as well as to provide extra surface area for muscle attachment. (In regard to the latter, this modification is considered functionally similar to the development of the bipartite light organ discussed above.)  Pygat. undulata and Pygat. tagensis lack the narrowed median posterior prolongation of ventrite 7. Both functions could be achieved in these species by the pronounced arching of the posterior half of ventrite 7. Reinforcing against muscle pull could be the function of the median carina between light organ halves in certain Colophotia. The dimple and hump on ventrite 7 of certain Medeopteryx are probably the result of the pressure of muscle pull on the median posterior projection of ventrite 7 and may constitute a form of reinforcing like the median carina of certain Colophotia. 

Areas of attachment of the dorsoventral muscles attaching tergite 7 to ventrite 7 are visible through the cuticle in pinned specimens of Triangulara sp. (mentioned as a presently unidentified Luciola sp. in Ballantyne, 1987b, Fig. 1 a, c). Such a strong attachment between ventrites and tergites would anchor the aedeagal sheath in position, akin to the ventral trough of tergite 8 outlined above. Sclerotia aquatilis (identified in Ballantyne, 1987b, Fig. 1g as L. japonica) has heavily sclerotized "hooks" in the intersegmental membrane between ventrites 7 and 9. These are a cuticularisation, probably secondary, in the region where one would expect to see remnants of ventrite 8 (Lawrence, pers. comm.). They provide area for muscle attachment and are characteristic of species in the genus Sclerotia (Ballantyne et al. 2015 Figs 29-31). 

Mechanical modifications in bent winged fireflies which could be a consequence of the development of the copulation clamp are also evident. The median ventral "trough" of tergite 8 housing the aedeagal sheath ensures that it and the aedeagus remain in a specific position as the tip of the female abdomen is drawn into the space between ventrite 7 and tergite 8. Positioning is critical if the clamp is to function correctly and not cause internal damage to the female (Wing et al., 1983). The lateral posterior corners of ventrite 7, which remain outside the female abdomen during copulation (Wing, pers. comm.), and the flanges on the ventral face of tergite 8 may manoeuvre the female abdomen into the correct position for a clamp to be effective. 

The bifurcate anterior margin of tergite 8 is prolonged anteriorly beneath tergite 7 in all Luciolinae males investigated, and provides extra surface area for muscle attachment, as well as accommodating the aedeagal sheath. This prolongation is most extreme in certain Colophotia species where the length appears to coincide with the very long aedeagal sheath. Only in these same Colophotia are the anterolateral corners of tergite 7 also prolonged although not to the extent of tergite 8. No other abdominal tergites are anteriorly prolonged. 

The prolongation of tergite 8 posteriorly, especially where it inclines ventrally, as in species of Pygoluciola, may contribute a mechanical advantage in physically deterring other males from attempting to copulate with an already coupled female. The "bizarre" hooks arising from the median posterior area of ventrite 7 in some Colophotia could function similarly. The possibility that the firefly encounters mechanical difficulty in extracting the aedeagus is suggested where prolongations and apical curvature of both ventrite 7 and tergite 8 occur. The area lateral to the median posterior projection of ventrite 7 in many of these species is quite open, and the aedeagus is probably extracted laterally. Modifications in Asymmetricata ovalis, As. circumdata (Ballantyne, 1987b, Fig. 1, d - f) where tergite 8 is asymmetrical suggest the aedeagus must be extracted dorsally because the more usual direction is blocked.

Luciolinae males have 6 visible abdominal ventrites (belonging to actual segments 2 - 7) with the light organ beneath the ventrites of segments 6 and 7. Males of species in other subfamilies (Photinus, Photuris, Aspisoma and Pyractomena spp.) have 7 visible abdominal sternites belonging to actual segments 2 - 8 with the light organ beneath segments 6 and 7, as it is in the Luciolinae. However sternite 8 is present and visible, although reduced. The loss of this eighth sternite in the Luciolinae was probably the catalyst for many of the modifications described here. 

In the Luciolinae males the aedeagal sheath is retracted within and between ventrite 7 and tergite 8. Any musculature to move this sheath will require surface area for attachment. 

In the anterior ventrites of Pteroptyx valida the ventral longitudinal muscles fan obliquely (Ballantyne 2001 Fig.46). The largest muscle blocks occur in segments 4 and 5. Ballantyne, 1987a, 1987b considered the arrangement of the ventral longitudinal muscles, especially in ventrite 7 would pull the median posterior projection of ventrite 7 against the deflexed elytral apices in a copulation clamp. However, Case (1984) described the flexion of the male abdomen where the terminal abdomen and light organ is displayed in the female's face. The arrangement of the ventral longitudinal muscles described above would achieve some bending of the abdomen around segments 4 and 5. The median posterior projection of ventrite 7 then becomes the final reinforcing point in the abdomen against which these muscles pull. Flexion of the abdomen is an important reproductive strategy for male fireflies (Lloyd, 1979a; Lloyd et al., 1989; Case, 1984) in leading to a "genital pocket" display which suggests the use of chemical signals in addition to light. The abdomen is also flexible enough to be able to be retracted (Wing et al., 1983 Fig. 3 shows the apex of the abdomen at rest anterior to the deflexed elytral apex.) The flexing movement probably developed first and the developments of ventrite 7, especially of the median posterior projection, followed partly as a consequence and partly for extra surface area for muscles that move the aedeagus and aedeagal sheath. 

Certain Medeopteryx having deflexed elytral apices have abdominal structures similar to those of Pteroptyx. If these abdominal modifications are the result of muscle insertions developed primarily to flex the abdomen, then such species are predisposed to development of a copulation clamp where some increase in surface area of the elytral apex is required. (Comparable modifications would be necessary to the female reproductive tract.) It is interesting that certain species (e.g. M. minor, P. truncata) have a relatively small deflexed elytral apex.

However, there are other aspects of the morphology of the male abdomen that need to be considered relative to the copulation clamp, which has been demonstrated only in two Pteroptyx species, valida and maipo. The critical feature may be the configuration of the median posterior projection of ventrite 7 in these species, which is a solid structure with a relatively flat dorsal surface. It is against this surface that the elytra engage with the female abdomen wedged between the two. If this interpretation is correct then we would not expect to see species with deflexed apices and hooked or bifurcate median posterior projections of ventrite 7 developing a copulation clamp. 

The median posterior projection of ventrite 7 often remains dorsally arched in certain pinned Pteroptyx. Dorsal arching of the posterior margin of abdominal ventrite 7 (excluding the posterolateral corners) occurs in some pinned Pyrophanes, where the elytral apex is not deflexed. Such a development in Pyrophanes does not suggest a copulation clamp, but rather that abdominal flexion occurs. 

The ventral longitudinal muscles that flex the abdomen require surface area for attachment. In the Luciolinae because of the loss of ventrite 8 they attach at least in part on ventrite 7. The area of the light organ in this ventrite is reduced and often bipartite. These muscles finally pull against the posterior margin, in particular the median posterior projection of ventrite 7, which is often well developed in Luciolinae males. Any further developments of the posterior margin of ventrite 7 and the extra surface area provided by the median posterior projection will provide extra surface area for attachment of the aedeagal sheath muscles, which would normally have inserted in ventrite 8.

While the male abdomen in many situations is thus predisposed to the arching necessary for a copulation clamp to function we see above that other features are necessary as well.

Such considerations are not obvious in the Lampyrinae and Photurinae where sternite 8 and its associated area for muscle attachment are present, and present a remarkable uniformity of structure of the terminal abdomen, where sternite 8 is free of the light organ and the aedeagal sheath is retracted into the terminal abdomen between sternite 8 and tergite 8. Here there is apparently no involvement of the terminal abdomen in the reproductive process. The complex nature of the aedeagus and the juxtaposition of various parts are strongly suggestive of structures like hooks and snips but in the absence of any reliably associated females (or indeed in most cases any females) we can only surmise at their function in the female reproductive tract especially the supposed manipulative abilities to ensure that that male's sperm is the only sperm to fertilise the female.

Summary of abdominal and aedeagal sheath modifications in the Luciolinae

1.  Although Luciolinae males are distinguished primarily by the presence of only 6 visible abdominal sternites/ventrites (belonging to actual abdominal segments 2 - 7), certain males possess remnants of sternite 1 as lateral cuticular plaques in an otherwise membranous area. 

2.  Many of the external modifications of the male terminal abdomen are not directly of copulatory significance, as previously supposed. They are instead external manifestations of the need for increased surface area for muscle attachment, and a form of reinforcing against muscle pull, which arise directly from the ventral longitudinal muscles that cause the abdomen to flex. Modifications are explained in this light. Other "mechanical" modifications not directly related to muscle attachment may follow as a consequence of muscle development in other areas. These are related to their indirect uses in a reproductive context. 

3.  Two explanations for such modifications are advanced. The first is the loss (or fusion with sternite 7) in Luciolinae males of abdominal sternite 8, and the consequent loss of a surface area for muscle attachment that this sternite presented. Most modifications in Luciolinae male abdomens can be attributed directly to this loss, although no explanation is offered. 

The second is the ability of the males to flex their abdomens. Because sternite 8 is absent a reduction in the light organ in sternite 7 may occur to allow for attachment of these muscles. This leads to a bipartite light organ or a reduction of the light organ area in sternite 7. The ventral longitudinal muscles ultimately pull against the median posterior projection of sternite 7 which provides extra surface area as well as a type of reinforcement against muscle pull.

4.  Understanding of the structure of both abdomen and aedeagal sheath allows predictions to be made about reproductive behaviour, much of which can be assessed against known behaviour patterns.

Table 1. Morphological characters of flightless Luciolinae females (expanded from Ballantyne & Lambkin 2009 Table 6, 130, 132–136).

A. 1 = colour pattern like that of male; 2 = colour pattern differs to that of male.

B. 1= elytra covering all but two segments of the abdomen; 2= elytra covering all but 4–5 segments of the abdomen; 3= elytra very short and almost all of the abdomen exposed.

C. 1= elytra with apical ridge; 2= elytra without apical ridge.

D. 1= elytra with visible interstitial lines; 2= elytra without visible interstitial lines.

E. 1= elytra contiguous for most of their length; 2= elytra divergent along sutural margins in apical ½ to 1/5; 3= elytra not contiguous

F. 1= hind wings longer than half fore wing length; 2 = hind wings shorter than half elytral length; 3= hind wings vestigial or absent. 

G. 1 = female can flit; 2 = female cannot fly

H. 1=width of anterior margin of MS = posterior width across combined MN plates; 2 = width of anterior margin of MS less than width across combined MN plates.

I. 1= pronotal outline like that of male; 2=outline modified

J. 1= Eleven antennomeres; 2= less than 11 antennomeres

K. 1= all antennomeres longer than wide; 2 = at least some antennomeres where L=W; 3= at least some antennomeres where L<W.

L. 1= mandibles well defined; 2= mandible reduced;

M. 1= minor physogastry; 2= major physogastry.

N. 1 = apical maxillary palpomere well defined; 2 = apical maxillary palpomere reduced.

O. Estimated capacity to feed: 1 = yes; 2 = no.

General features of lucioline larvae 

Larvae are most easily recognised by the production of light from paired light organs on their 8th abdominal segment, the elongate slender body form consisting of three thoracic and 9 abdominal segments, and especially the features of the head capsule.

The following definitions of mode of life for larval Luciolinae are used:

Aquatic: living under water and with obvious adaptations for aquatic life; either with lateral abdominal gills (Aquatica, Nipponoluciola) or metapneustic (Sclerotia), lacking gills. 

Semi-aquatic: usually living in riparian environments and regularly entering the water in search of prey; lacking obvious adaptations to aquatic life, such as gills.

Terrestrial: lacking gills and any specialized respiratory and behavioural modifications for an aquatic life.

General larval morphology: With 3 thoracic and 9 obvious abdominal segments; a narrow ring of cuticle at the posterior end of segment 9 has been attributed to segment 10 but may only be visible from beneath. Elongate, tapering at the front and behind, somewhat flattened. Larval are of several types: terrestrial larvae have the ventral surface subdivided as described below and may have the dorsal plates expanded laterally; Abscondita and Pygoluciola have the dorsal surface heavily sclerotised; Sclerotialarvae have both dorsal and ventral surfaces heavily sclerotised, subdivisions of the ventral surface are difficult to recogniseand they respire by a pair of spiracles on their eighth abdominal segment; aquatic larvae of Aquaticaand Nipponoluciola have abdominal segments 1–8 with lateral tracheal gills which are forked and compound, with a non functional spiracle at the end of the shorter branch; subdivisions of the ventral surface are difficult to recognise as the body is so soft.

The ventral surface of the prothorax is little differentiated, with very narrow strips of cuticle dorsal and lateral to coxae 1 representing prothoracic episterna and epimera. In the remaining segments and where ventral sclerites are visible, a lateral pleural suture delimits laterotergites above in the thorax and abdomen. In the thorax the median ventral surface of both meso and metathorax is subdivided into two areas by a sternocostal suture running anterior to the coxae, an anterior basisternum with laterotergites at the sides in the mesothorax; (in terrestrial larvae these mesothoracic laterotergites bear functional biforous spiracles); a posterior median subrectangular sternellum bears the legs and is margined laterally by laterotergites; the episterna and epimera of both the meso and metathorax are visible above the coxae of the meso and metathoracic legs as thin dark sclerotised plates. This subdivision does not extend to the dorsal surface. In the ventral surface of abdominal segments 1–8 a median subrectangular area is attributed to the sternum; this is margined laterally by elongate narrow paired laterosternites, which are delimited by folds from the median sternal plate below, and the laterotergites above; laterotergites of segments 1–8 either bear spiracles or branched gills. Eversible branched defensive organs arise at the sides of the meso and metathorax, and abdominal segments 1– 8, in the membrane at the sides of the terga of those segments and above the laterotergites of the abdomen in aquatic species.

The head is subparallel sided, dorsoventrally flattened, prognathous, well sclerotised, with an ocellus at each side; not visible when retracted into the prothoracic cavity; extensible neck membrane forming two layered envelope around retracted head; capable of considerable extension beyond the anterior protergal margin; head capsule divisible into median dorsal frontoclypeus, bounded laterally by the U shaped frontal arms of the ecdysial line (=epicranial suture); lateral parietal plates at the sides of the frontoclypeus are separated behind by the epicranial stem and are reflexed ventrally but not meeting; maxillae and labium fused forming a maxillolabial complex covering most of ventral head area. 

Antennae are slender, cylindrical, 3 segmented, with elongated scape and pedicel, and apical very short (3rd) segment (equivalent to the flagellum in the adult), with an apical sensilla, subequal in length to adjacent sense cone; an elongate "articulating membrane" forms a two layered envelope around the retracted antenna in the same way as the head itself is enveloped by a membrane. 

Mouthparts are well developed and similar in form to those of the adults; mandibles falcate, strongly sclerotized; densely covered in fine hair along outer margins; densely pubescent along basal half of inner margins; perforated along the length by a fine canal that opens on the outer margin just behind the apex; some species have one or two basal inner mandibular teeth. Maxillae with short, squat, four segmented palp bearing sense organs on segment 4; basal segment (which may be interpreted as the palpifer) large and well defined, segments 2 and 3 very short and diminishing in width towards apex, apical segment longer and narrower than palpomere 3; palp may obscure galea, which is two segmented, bearing long and short setae at apex, and on its inner margin an elongate, flattened, dense profusion of anteromedially directed hairs (lacinia); cardo well defined, articulating with broad elongate stipes; fused along its outer edges with the reflexed head margins, and along its inner margins with the median labium. Labium with two segmented labial palpi, bearing sense organs on segment 2, and arising at anterolateral corners of small prementum which lacks a ligula. 

Legs are four segmented - short cylindrical coxae with bases widely separated; elongate trochanters joining femora obliquely; tibiotarsus terminated by a single claw. In contrast with previous treatments the leg segments are attributed to coxa, trochanter, femur and tibiotarsus. 

If defensive organs are present they occur in aquatic larvae as 10 pairs of similar pale white, forked eversible organs located laterally on the meso- and metathorax, and above the tracheal gills on each of the 8 abdominal segments; these organs arise in the thorax in folds of membrane on the upper side of the laterotergites and just below the lateral margins of the tergal plates, and in the abdomen above the abdominal laterotergites and below the lateral margins of the tergal plates.

Pygopodia arise in all larvae from the end of the abdomen (either the visible 9th (or the largely invisible 10thsegment) and aid in progression; they are tubular and eversible holdfast organs bearing recurved hooks along their length.

Key to genera and species of lucioline larvae (Figure references are to Fu et al. 2012 Zootaxa 3405)

1. Aquatic (metapneustic or with gills along the sides of the abdomen) (Figs 73–86) ………..…………………....……………2

Terrestrial/semiaquatic (lacking gills) (Figs 87-90) …….........................................................................………………………..9

2. Metapneustic in later instars; hard-bodied with no obvious membranous areas; back swimmers just below water surface 

………….........................................................…Sclerotia substriata (Gorham) /Scl. aquatilis (Thancharoen) (Figs 83, 84)

With gills arising from the sides of abdominal segments 1–8 (Figs 73-86)..............................................................................3

3.  Protergum lacking marginal pale markings ……....Aq. hydrophila (Jeng et al.) 

Protergum always with some pale lateral margins ……………………………..4

4. Protergum with 2 pale markings only (at anterolateral corners) (Fig. 77) ………Aq. leii (Fu et Ballantyne)

Protergum with more than 2 pale markings around margins …………………….5

5.  Protergum sub-parallel sided ; with four separate pale marks at anterolateral corners and along lateral margin anterior to the posterolateral corners (Fig. 75) ………………..……………………..…………………………Aq. lateralis (Motsch.) 

Protergum with lateral margins not sub-parallel sided; pale markings not as above  ............6

6.  Median dark marking on protergum prolonged narrowly anteriorly and posteriorly to meet anterior and posterior margins (Fig. 81) …Nipponoluciola cruciata (Motsch. )

Median dark marking on protergum not prolonged narrowly anteriorly, median dark area may assume the shape of a cross with wide anterior and lateral arms, thus protergum having four discrete pale markings at anterolateral and posterolateral corners ……………………..……..7

7.  Protergum mainly dark marked, with four discrete pale areas at anterolateral and posterolateral corners; no pale markings on remaining terga; median line narrow (Fig. 73) ………………………………………………………………………… .Aq. ficta (Olivier) 

Protergum either marked as above or with pale areas extending obliquely across posterolateral corners to almost meet in median line; always with pale markings on remaining terga; median line narrow or wide ………………………………..8

8.  Protergum mainly dark, with four discrete pale areas at anterolateral and posterolateral corners; terga of body segments 2–11 very small and separated by wide median line; small pale markings at posterolateral corners of terga of body segments 2–11; terga of body segments 10, 11 lacking pale lateral margins (Ohba et al. 1994: 17, Fig.1) …………………………………………………….Nipponoluciola. owadai (Sâto et Kimura)

Protergum mainly dark with extensive pale markings obliquely across posterolateral corners; terga of body segments 2–11 large, not widely separated by narrow median line; extensive pale markings across most of posterior margins of body segments 2–8 or 9; lateral margins of terga of body segments 10, 11 pale (Fig. 79)…….Aq. wuhana (Fu etBallantyne) 

9.  Semiaquatic – living near shallow bodies of water and able to enter them and submerge for long periods; lacking gills; dorsal body plates very heavily sclerotised and lacking membranous areas; mandibles with 2 inner teeth (Fu & Ballantyne 2008; Figs 2–4, 23–25) ….………………………….……………………………Pygoluciola qingyu Fu et Ballantyne

Dorsal body plates are usually dark coloured, and may not be well sclerotised; mandibles with single tooth, or not toothed; probably terrestrial….………………………10

10.  Mode of life not determined, probably terrestrial; lacking gills; dorsal body plates very heavily sclerotised and lacking membranous areas; mandibles with a single tooth ……………………………Abscondita cerata, praeusta, terminalis, Pyg. cowleyi

Terrestrial; lacking gills; dorsal body plates not usually very heavily sclerotised;  mandibles not toothed……………………………………...…………………..11 

11.  Tergal margins not laterally explanate; laterotergites often visible at sides of body  when specimen viewed from above.(e.g. Figs 89, 90) ...................12

Tergal margins laterally explanate, usually along lateral margins, sometimes only  at posterolateral corners (e.g. Figs 87, 88)…………………………………….13

12.  Dorsal body plates usually dark coloured and reaching to sides of terga  ………..........................................Pteroptyx and Colophotia spp. (e.g. Fig. 89)

Dorsal body entirely pale, tergal plates pale coloured and not reaching to sides of  terga …………………………...………………………………Curtos spp.

13.  Thoracic and/or abdominal terga prolonged at posterolateral corners ………..14

All tergal lateral margins widely explanate, not prolonged, except for terminal tergum...........................Magnalata sp., Atyphella spp., Luciola parvula, L. filiformis, L. kagiana, Lloydiella sp., Asymmetricata circumdata (Figs 87, 88)

14. Lateral margins of thoracic terga very broad, not prolonged except for very shortpointed posterolateral corners on terga 2, 3; lateral margins of abdominal terga 1–8 narrowly prolonged (Fu et al. 2012 Figs 5, 6) ……………………………………………………….…….Emeia pseudosauteri

Lateral margins of both thoracic and abdominal terga narrowly prolonged (Fu et al. 2012 Figs 50, 51) …………………………………….Luciola hypocrita