LAMPYRIDAE Rafinesque, 1815

Fireflies

The only bioluminescent animals in the UK, these beetles occur in grassland habitats. During their short season the glowing females are highly conspicuous among tussocks at night.

POLYPHAGA Emery, 1886

ELATEROIDEA Leach, 1815

3

3

5-23mm

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Introduction

These are the classic fireflies and glow worms, recognized in the field by their nocturnal flashing or continuous light which are generally used in courtship, although the family also includes many non-luminescent species. In males the lights often appear as two pale ventrites, in many they also have a laterally and anteriorly expanded pronotum which covers the head and seems to act to block light from above, many are drab and soft-bodied with flat elytra that lack epipleura, and when handled many release drops of pale haemolymph which tends to be poisonous and acts as a defence against predators. Females as well as most early stages of many species are also luminescent. Species occur in all major regions of the world, including many islands, but are absent from New Zealand and most of Australia. The family includes more than 2000 species in about 110 genera but these numbers are likely to increase greatly as many more, perhaps 2 or 3 times as many, await description in museums throughout the world. The greatest diversity is in tropical areas and about half of all known species occur in the Neotropical region, about 170 occur in the Nearctic and of the 30 European species only 3 extend into central and northern areas. The African fauna includes about 200 species.  The classification remains very problematic at all levels e.g. the Rhagophthalmidae, an Old World family with bioluminescent species and larviform females are obviously elateroid and may well eventually be included, the odd genus Pterotus LeConte, 1859, with 2 Nearctic species, is often placed in its own subfamily, and Phausis LeConte, 1851, usually included in the Lampyrinae Latreille, 1817, may represent a distinct family. In general the family falls naturally into 2 groups, both classified into several subfamilies and tribes; Lampyrinae and Photurinae Lacordaire, 1857 include Nearctic and Eurasian species and another group, predominantly Asian, is divided into several subfamilies, and both groups have a wider world distribution. Many subfamilies etc. have been proposed but only 5 are generally, albeit variously, accepted. Ototretinae McDermot, 1964 is often included but not universally accepted, species occur in North America, Eurasia and the Oriental region; they are not luminescent but use pheromones to attract mates. The group includes about 200 species in 20 genera. The monotypic genus Ototretadrilus Pic, 1921, formerly constituting the distinct subfamily Ototretadrilinae  Crowson, 1972 has been transferred

to the previous subfamily. Photurinae is a New World group occurring from Canada to Argentina, adults use ‘flashing’ rather than continuously glowing light to attract mates, and females of some species of Photuris Dejean, 1833 imitate the flashes of other fireflies to attract and then predate them. Some are well-known e.g. P. pennsylvanica DeGeer, 1774 is the state insect of Pennsylvania. Luciolinae Lacordaire, 1857 is one of the largest subfamilies with around 500 species and occurs throughout temperate Eurasia, the Oriental region and through Southeast Asia to Australasia. The African fauna includes about 100 species while more than 100 are Australasian. They are flashing species and some have become a tourist attraction e.g. some Pteroptyx Olivier (known as bent-winged fireflies due to the reflexed elytral apices in the males, used in mating) occur in huge numbers beside rivers in Malaysia (etc.), they begin flashing randomly but soon synchronize over wide areas, producing spectacular visual displays which may include several species.  Pterotinae LeConte, 1861 is Nearctic and includes several species of the single genus Pterotus LeConte, 1861; males are not luminescent but the larvaeform females glow continuously. Lampyrinae Latreille, 1817 is probably the largest subfamily although historically it has been used as a dumping ground for awkward taxa e.g. the small monogeneric subfamily Cyphonocerinae Crowson, with about 25 east Asian species, was formerly included, several genera such as Amydetes Hoffmansegg, 1870, Lamprigera Motschulsky, 1853 and Lucidina Gorham, 1883 are only uncertainly placed and the genus Pristolycus Gorham, 1883 may be better included in the Luciolinae. Nonetheless, even in a narrower, more monophyletic sense it is a very diverse group including flashing as well as continuously glowing species. Ancestral Lampyrinae probably lacked luminescence, or had very poorly developed signalling, and several modern lineages have returned to pheromone communication independently. The greatest diversity is in the Neotropical region; more than 450 are recorded from South America and about 180 from Central America, about 80 are Nearctic and more than 120 are recorded from Africa, almost 200 are recorded from the Palaearctic region of which the majority occur in southern and eastern Asia. The group is absent from Australia and in Europe most, about 25, occur in southern regions.

Description

Most species are elongate, only a very few are broadly oval, and drab coloured, black to brown or pale testaceous to creamy, in many with various red, yellow or black markings to the pronotum and elytra and the majority are small to medium sized, 4-18mm. Head hypognathous, usually concealed beneath the pronotum when at rest and extended forward when active, elongate and smooth or variously punctured, labrum small and often indistinct i.e. fused to the clypeus, mandibles usually large, curved and sharp but sometimes greatly reduced. Maxillary palpi 4-segmented and variously modified but the terminal segment is usually widely dilated, labial palpi 3-segmented with the terminal segment developed, sometimes securiform. Antennae 8-13 segmented but usually with 11, filiform to serrate or pectinate and inserted on the inner margins of the eyes above the base of the mandibles. Eyes occupying most of the head from above, convex and large, sometimes very large and adapted to view ventrally, sometimes almost meeting below. Pronotum distinctive and often a good guide to the family; expanded to conceal the head; semicircular to elongate, sometimes almost pentagonal or triangular. Surface smooth or punctured and without major structure although there are often basal fovea or a longitudinal median impression, often distinctly marked or coloured and in some with translucent ‘windows’ anteriorly above the eyes. Prosternum and mesosternum short, procoxal cavities contiguous and open behind, mesocoxal cavities contiguous, metasternum broad and long, metepisternal margin straight, only weakly, if at all, curved or sinuate, metacoxal cavities transverse, open and contiguous. Scutellum usually obvious, often relatively large and usually triangular. Pro- and mesocoxae large, conical and contiguous. Trochanters quadrate or nearly so and obliquely connected to the femora, all femora visible from above, relatively long and usually to some extent flattened and swollen. Tibiae long and slender, only weakly expanded towards the apex, without teeth or spurs internally and with or without terminal spurs. Tarsi 5-5-5; 1-3 slender or weakly expanded apically and the fourth variously lobed. Claws smooth, simply pointed or bifid, and sometimes with a basal tooth. Elytra elongate and meeting to the apex or variously diverging, generally with weakly convex shoulders and tapering, parallel-sided or broadened around the middle, smooth and variously punctured and pubescent, without distinct striae but often with longitudinal costae, often explanate and lacking epipleura. The European Phosphaenus hemipterus (Goeze, 1777) seems to be unique in having consistently brachypterous males with reduced elytra. Male abdomen with 7 ventrites, in some the terminal tergites are expanded laterally and visible from below. Luminous organs, visible as pale areas, are usually present in one or both sexes; their number and placement along the abdomen varies widely. Sexual dimorphism exists in many species, usually the female have reduced wings but this condition is known to be polymorphic; in the Nearctic Pyropyga nigricans (Say, 1823) both males and females, or sometimes only females from some sites have reduced wings and elytra. Females of some species superficially resemble their larvae but whether they are truly larviform is uncertain. Luminous organs also differ between the sexes in placement and number and there may also be structural differences.

Larvae are generally distinctive with all body segments well-defined and often individually expanded laterally, fully grown they are between 10 and 25mm, elongate-oval and well-sclerotized, most are flattened and drab coloured with pale markings and luminous organs; so far as is known all are luminescent and most have a pair of ‘lanterns’ at the abdominal apex. They have 12 distinct dorsal sclerites; the head is elongate with prognathous mouthparts, long channelled mandibles and retractable 3-segmented antennae, it is usually retracted into the prothorax but extended when feeding. The prothorax is usually longer than the meso- and metathorax which are quadrate or transverse and a little wider. Legs 5-segmented with terminal tarsunguli. Abdomen 10-segmented with paired ‘lanterns’ at least on the eighth segment. Segments 1-8 have paired annular spiracles and the eighth segment has an eversible structure, the pygopodium, which is used for cleaning the body after feeding.

A
B
C

Lampyris noctiluca adult female (A), Pupa (B), and final instar Larva (C).

Ecology

Lampyrids occur in a wide range of habitats, on a world basis many are common in wetland marginal and damp woodland situations where the larval food is abundant, many occur in coastal wetlands including salt marshes and mangrove swamps and only relatively few occur in arid regions. The best known species are nocturnal and luminescent but many are diurnal and do not produce light although some diurnal species living in dense and shaded forests may be also be luminescent. In general fully-winged adults of both sexes are good fliers. All developmental stages glow at least to some extent; eggs of many glow due to chemicals deposited onto the chorion during oviposition, larvae use luminescence as an aposematic warning to predators, and in general lampyrids are distasteful or even poisonous, at least to vertebrates, as they contain lucibufagins, a group of steroid pyrones similar to cardiotonic chemicals which occur in poisonous amphibians. Adults of many species are short-lived but may have a long season due to protracted emergence, in many cases they do not feed and some have atrophied mouthparts, they mature quickly and mate soon after emerging and females lay batches of eggs on or just below the ground surface. Larvae emerge after a week or two and develop through the summer, they pass through several instars and many are mature within a single season. The term glow worm generally refers to the common European Lampyris noctiluca (Linnaeus, 1758) in which the larvae and non-flying females glow intensely while the flying males glow intermittently and only weakly. Larvae may be general predators of other insects and small animals, detritivores or even vegetarian but many are specialist predators with grooved mandibles adapted to inject digestive juices into their prey, many specialize in molluscs or worms and some marginal species enter the water to predate aquatic gastropods etc. which they stun and take to the bank or up into vegetation to consume. Larvae can be terrestrial, semi-aquatic or completely aquatic in which case they have ventral gills on the terminal abdominal segment, but in all cases pupation occurs out of water. In permanently wet or periodically inundated marginal situations some larvae construct sub-spherical dwelling chambers from soft substrate. So far as is known larvae find prey by following scent trails. Most overwinter as larvae, generally once but sometimes over several winters, and pupate in the spring, they usually burrow into the ground to pupate but some do so among leaf-litter, under debris or among decaying wood or bark. Glowing usually persists in the pupal stage but is lost as the adults of non-glowing species develop. Adults generally emerge within three weeks of pupation.

Bioluminescence

Lampyrids produce a cold light entirely within the visible spectrum, generally between 500 and 670nm, the colours produced ranging from yellow to green or pink. The luminescent reaction is catalyzed by the enzyme luciferase, oxidizing the pigment D-luciferin in the presence of ATP and magnesium ions, photons being released when oxyluciferin relaxes. The sensitivity of this reaction has resulted in its use in forensics and medicine to detect magnesium or ATP. The primary function of this bioluminescence is thought to lie in mate attraction and selection, the frequency, strength and pattern of light signalling providing information regarding the species and condition of the signaller. Compared with pheromone-based communication systems the use of light is much more energy efficient, especially as it also signals warnings to predators, and as such is readily maintained in an evolutionary system. In some species the female simply glows to attract a mate but in general the males glow brightest. Colour is thought to have no effect; a given species will react to certain wavelengths and flashing patterns, whether from an appropriate mate or from an artificial light source, and it seems that different colours are more efficient at certain times; greens and yellows at night and oranges at dusk or dawn. Sensitivity to colour seems not to be neurophysiological but rather caused by coloured filter pigments in the retina. Mostly the light is continuously glowing and be accompanied by pheromones for longer-distance communication, but many elaborate signalling routines have evolved; usually the males flash while in flight and the females, waiting below or on adjacent vegetation, flash in response, males fly ever closer while the pair continue flashing to each other until union is achieved. The strength and duration of flashing as well as the patterns of light produced when the male turns in flight convey information to the females and so may lead to sexual selection. In large populations flashing becomes synchronized and this can be continuous, where all individuals flash in unison, or discontinuous where waves of flashing lights pass along foliage beside river banks etc. and such displays may include more than one species. Luminescent organs are highly innervated and flashing is controlled by the nervous system in response to visual cues, the synchrony seen in aggregations is under the dynamic control of a ‘pacemaker’, flashing patterns are inherent to the nervous system but fine control i.e. speed, strength and duration of flashes also depends on the environment. Aggressive mimicry occurs in certain species where females can flash to attract males of other species and predate them, to attract conspecifics males they revert to their natural flashing patter. This system has become ridiculously evolved in some species of Photuris where males also mimic males of other species in order to induce females to flash i.e. they have hijacked the flashing pattern of another species in order to find and attract mates.

About 70 species occur in the Western Palaearctic of which 30 are European but only 3 extend north into central and northern Europe and all 3 have been recorded from the UK, all are included in the Lampyrinae and are distinct among our fauna although the larviform females might be confused with female Drilus. Our species are readily distinguished with this key.

UK Species

Lamprohiza splendidula  plate © 2013 Dr. med. Arved Lompe http://www.coleo-net.de/coleo/html/start.htm

Further Reading

Icones insectorum Europae centralis 5

Bocak, L. Bocakova, M.

Introduction to European Lampyridae and other families.

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