Blister Beetles

Zonitis sayi, copyright Carol Davis.

This is a blister beetle of the genus Zonitis. Blister beetles, the family Meloidae, get their name from their production of cantharidin, a defensive chemical that can burn the skin of would-be predators. Zonitis is a widespread genus of blister beetles with over 100 species described from around the world. However, it should be noted that its wide distribution may relate to the genus being poorly defined and future revisions may divide its members between other genera (as I believe has already happened for the Australasian 'Zonitis'). As it is, Zonitis species are characterised by fully developed elytra and functional wings, and cleft tarsal claws with two rows of teeth on the upper section (Enns 1956). Adult Zonitis are flower-feeders, visiting composite plants (i.e. daisies and similar plants), and some species have the mouthparts modified into a tube for sucking nectar.

Most blister beetles exhibit what is known as hypermetamorphism or hypermetaboly, where the larvae pass through morphologically differentiated stages before reaching pupation. Zonitis species develop as parasitoids or kleptoparasites of bees. Females lay large numbers of eggs (up to and exceeding 500 in a batch) on their host plant, most commonly on the flowers though sometimes on the undersides of leaves. The eggs hatch into active, long-legged larvae that attach to bees visiting the flowers and so get carried to the bee's nest. Once there, they moult into a less mobile stage and feed on the food stores laid aside for the bee's larva, and potentially on the larva itself. In the North American species Zonitis atripennis flavida, the beetle larva completes its development in a single cell but European species consume the contents of two bee cells before reaching maturity. Following the initial active instar, meloid larvae pass through four feeding instars before entering a quiescent, immobile stage called the hypnotheca or prepupa. The hypnotheca moults into another feeding instar before the larva finally enters the pupal stage (Bologna et al. 2008). What the point (if anything) of the hypnotheca is, I have no idea. However, it is worth noting that hypnothecae of another meloid species, Hornia boharti, have been recorded surviving for multiple years without feeding before moulting to the next instar.

Once adults emerge from the host cell, they of course disperse to conduct their own affairs. Natural history data is patchy but indications are that many species are picky in their choice of host plant. From an economic perspective, their damaging role as a parasite of pollinating bees may be partially counterbalanced by their potential role as pollinators in their own right, but who can say which way the scales lean?

REFERENCES

Bologna, M. A., M. Oliverio, M. Pitzalis & P. Mariottini. 2008. Phylogeny and evolutionary history of the blister beetles (Coleoptera, Meloidae). Molecular Phylogenetics and Evolution 48: 679–693.

Enns, W. R. 1956. A revision of the genera Nemognatha, Zonitis, and Pseudozonitis (Coleoptera, Meloidae) in America north of Mexico, with a proposed new genus. University of Kansas Science Bulletin 37 (2): 685–909.

Cicadomorpha

Textbooks will tell you that the term 'bug' should be restricted to insects of the order Hemiptera though, as I've noted before, I don't know if I've ever met anyone who actually used the word that way. For many people, one of the groups of actual bugs that they are most likely to be aware of are members of the Cicadomorpha.

Tasmanian hairy cicada Tettigarcta tomentosa, copyright Simon Grove.

Cicadomorphs include the cicadas (Cicadoidea), leafhoppers (Membracoidea) and spittlebugs (Cercopoidea). As a group, they are distinguished by an enlarged postclypeus (the upper part of the front of the head below the antennae), simple antennae with a whip-like flagellum, and small and narrowly placed mid-coxae (Dietrich 2005). The enlarged postclypeus is associated with adaptations for feeding on xylem, deeper in the plant stem than many other plant-sucking bugs prefer, though derived subgroups of the leafhoppers have changed back to phloem or parenchyma. Well over 30,000 species of cicadomorph are known from around the world. Cicadas can be readily distinguished from other cicadomorphs by their possession of three ocelli in a triangle on the top of the head whereas leafhoppers and spittlebugs have only two or no ocelli.

Male bladder cicada Cystosoma saundersii, one of the world's more ridiculous animals, from Brisbane Insects.

Cicadas are best known, of course, for their singing. The songs are produced by a pair of membranous 'drums', the tymbals, at the base of the abdomen; muscular vibration of the membranes produces the sound. In most cicadas, only the male possesses these tymbals. However, both sexes possess tymbals in the hairy cicadas Tettigarcta, two species found in alpine regions in south-eastern Australia. Hairy cicadas also differ from the remaining cicadas in other ways, most notably in lacking the well-developed tympana on the underside of the abdomen that typical cicadas hear with (hairy cicadas have simpler hearing organs in their place). As a result, Tettigarcta is placed in its own distinct family, sister group to the remaining cicadas in the Cicadidae. Though now restricted to Australia, fossil species from the Mesozoic and Palaeogene of other parts of the world have also been placed in the Tettigarctidae (Shcherbakov 2008); however, they are mostly so placed on the basis of shared primitive rather than derived features and may well represent stem taxa for Cicadoidea as a whole. Other derived features of the cicadas proper in the Cicadidae include gas-filled chambers in the abdomen that resonate the calls produced by the tymbals. In males of another Australian species, the bladder cicada Cystosoma saundersii, these resonating chambers reach a remarkable size and the entire abdomen looks to have been blown up like a beach ball.

Froghopper Cercopis vulnerata, copyright Richard Bartz.

The spittlebugs or froghoppers of the Cercopoidea are smaller cicadomorphs, distinguished from species of the Membracoidea by their short and cylindrical (rather than long and quadrate) hind tibiae. The name 'spittlebug' refers to the nymphs of these bugs living covered with a protective covering of foam. In one family, the Machaerotidae, the nymph produces a calcareous tube around itself that it fills with fluid. The foam or fluid used for protection by cercopoids is primarily composed of the nymph's own excrement: the xylem fluids that they feed on are mostly water, after all, so they produce a large quantity of watery excreta.

Mango leafhopper Idioscopus nagpurensis, one of the world's many, many species of Cicadellidae, copyright Arian Suresh.

The third main subgroup of the cicadomorphs, the Membracoidea, is by far the most diverse, particularly the largest family Cicadellidae (leafhoppers). My own impression from my experience of collecting insects in various locations is that cicadellids are just everywhere. Over 20,000 species of this family have been described to date, and it has been estimated that the true number may be much higher. For instance, at one location in North America close to 100 species of a single genus Erythroneura have been recorded from a single plant (Dietrich 2002). Just how such a high diversity of closely related species can live in such close proximity remains a largely unanswered question, though some studies have apparently suggested the possibility of very fine micro-habitat partitions (making sense of the great mass of cicadellid diversity is not helped by many species exhibiting dimorphism between flying and flightless forms, similar to that I recently described for delphacids). Another notable feature of cicadellids is the protection of brochosomes, tiny, hollow, soccerball-like granules constructed of protein nets with which the leafhopper coats itself after moulting. The hydrophobic brochosomes help to keep the hopper free of water droplets and its own wet, sticky excreta. They may also serve other protective functions: females will coat newly laid eggs with a layer of brochosomes that may serve to prevent egg parasitoids such as micro-wasps from attacking the eggs.

Membracid leafhopper Cladonota benitzei, copyright P. Lahmann.

The membracoids also include the Membracidae, renowned for the remarkable appearance of the pronotal shield (the top and front of the thorax) in many species. In more humble membracids, the pronotum may form a high mound or pillar, but in others it may extend into bizarre arrangements of globules and branched spines hanging above the leafhopper like a baroque chandelier. Again, just what the purpose of this extravagant morphology is remains unknown but many authors have proposed some sort of protective function. It has been suggested that pronotal projections may help membracids mimic part of their host plant, or potential predators such as parasitic wasps. Alternatively, they mean that potential predators such as birds find the hopper just too hard to swallow.

REFERENCES

Dietrich, C. H. 2002. Evolution of Cicadomorpha (Insecta, Hemiptera). Denisia, Neue Folge 4 (176): 155–170.

Dietrich, C. H. 2005. Keys to the families of Cicadomorpha and subfamilies and tribes of Cicadellidae (Hemiptera: Auchenorrhyncha). Florida Entomologist 88 (4): 502–517.

Shcherbakov, D. E. 2008. Review of the fossil and extant genera of the cicada family Tettigarctidae (Hemiptera: Cicadoidea). Russian Entomological Journal 17 (4): 343–348.

The Colours of Rot

Bracket fungi Fomitopsis pinicola, copyright Marek Novotnak.

Apart from those species readily purchased at the supermarket, perhaps the macrofungi most likely to be encountered by the average person are the brackets. Bracket fungi are the hard, woody, shelf-like fungi that may be found growing from tree-stumps and fallen logs. Whereas other fungal fruiting bodies may emerge, release their spores, and collapse away within a matter of hours, those produced by bracket fungi (properly known as 'conks', apparently) may persist for years with a new layer of reproductive tissue added each cycle.

Phlebiopsis gigantea, a resupinate member of the Polyporales, copyright Jerzy Opioła.

The majority of brackets belong to the fungal order Polyporales, one of the major subgroups of the basidiomycetes with about 1800 known species (Binder et al. 2013). While brackets may be the most familiar Polyporales, the order is morphologically diverse. Indeed, no one morphological feature characterises the Polyporales as currently recognised; it has only been recognised as a clade following the advent of molecular analyses. Some members of the Polyporales produce persistent fruiting bodies like brackets, others are more ephemeral. They may be sessile and shelf-like, or they may be raised on a stalk. The spore-producing layer may appear as minute pores, as gills, as protruding teeth, or may be entirely smooth. There are also a large number of Polyporales species that are what is known as resupinate: that is, they don't produce discrete fruiting bodies at all. Instead, the reproductive structures are produced as a more or less undifferentiated crust spreading over their substrate.

Hexagonal-pored polypore Polyporus alveolaris, copyright Andreas Kunze.

The greater number of Polyporales are associated with decaying wood; they play an integral role in breaking down and releasing nutrients that might otherwise be locked away from environmental cycles. Most species only grow on wood that is already deceased but there are some that are pathogenic on living trees. Based on the appearance of the wood being broken down, Polyporales may be divided between 'white-rot' and 'brown-rot' species. The difference is not merely an aesthetic one. Wood is made up primarily of two organic polymers, cellulose and lignin. Both these chemicals are difficult to metabolise (we ourselves, for instance, cannot digest either) but lignin is a particularly tough nut to crack. White-rot fungi are able to digest both cellulose and lignin but brown-rot fungi digest the cellulose only. White-rot fungi extract more nutrients from the wood overall but brown-rot fungi extract nutrients faster. And while the efforts of white-rot fungi may result in almost the entire carbon quotient of the wood being released to the environment, brown-rot fungi leave a lignin-rich residue that is largely indigestable by any other organism. Genomes have been sequenced from both white- and brown-rot taxa and a fair amount of effort has been invested into studying the different chemical pathways underlying the different rot types.

Caulifower fungus Sparassis brevipes, copyright AL'S.

Phylogenetically speaking, Justo et al. (2017) recently recognised eighteen families within Polyporales corresponding to well-established molecular clades (plus a handful of taxa that could not yet be confidently placed in a 'family') but these show the same challenges to morphological characterisation as the order as a whole. Many of these families include both fruiting and resupinate taxa, and transitions in fruiting body morphology are the rule more than the exception. Interestingly, one 'morphological' feature that does show a fair degree of phylogenetic consistency is the rot-type. It seems clear that the ancestor of the Polyporales was a white-rot fungus with the majority of brown-rot fungi forming a single clade within the order. Only one known brown-rot fungus genus , Lentiporus, definitely evolved separately from the rest (another genus, Auriporia, may or may not represent a further origin of brown rot). One question that remains to be answered is whether the chemical basis of brown rot in Laetiporus is the same as that in the main brown-rot clade.

Ganoderma pfeifferi, copyright Bloodworm.

Apart from their role in breaking down wood, not too many Polyporales have a direct economic significance. Some, notably the lingzhi Ganoderma lucidum, are grown commercially for use in Chinese medicine. Some species with more fleshy fruiting bodies are edible: notable examples include the cauliflower fungi Sparassis species and the chicken of the woods Laetiporus sulphureus (guess what it's supposed to taste like). According to its Wikipedia page, chicken of the woods may cause a toxic reaction to some diners but there seems to be some question about whether this is due to toxins produced by the fungus itself or whether the fungus is absorbing toxins contained in the wood it is growing from. For other polypores, the question of toxicity may be rendered moot by the fact that any attempt to eat one would break one's teeth.

REFERENCES

Binder, M., A. Justo, R. Riley, A. Salamov, F. Lopez-Giraldez, E. Sjökvist, A. Copeland, B. Foster, H. Sun, E. Larsson, K.-H. Larsson, J. Townsend, I. V. Grigoriev & D. S. Hibbett. 2013. Phylogenetic and phylogenomic overview of the Polyporales. Mycologia 105 (6): 1350–1373.

Justo, A., O. Miettinen, D. Floudas, B. Ortiz-Santana, E. Sjökvist, D. Lindner, K. Nakasone, T. Niemelä, K.-H. Larsson, L. Ryvarden & D. S. Hibbett. 2017. A revised family-level classification of the Polyporales (Basidiomycota). Fungal Biology 121: 798–824.

Meandering Forams

Specimen of Meandropsina vidali, showing the patterning on the external surface, from Loeblich & Tappan (1964).

There are some taxonomic names that just instantly bring up a mental image of the sort of organism to which they refer. For my part, I've always felt that Meandropsina is one of those names. The Meandropsinidae are another family of relatively large and complex foraminifera (growing up to a number of millimetres across) that are known only from the Upper Cretaceous. The several genera of the family are predominantly European, with only the genus Fallotia also known from the West Indies.

Cross-section of Meandropsina vidali, from Loeblich & Tappan (1964).

Meandropsinids are (as far as I know) more or less lenticular in shape with chambers enrolled in a flat spiral. The name of the type genus Meandropsina refers to the way that the outer margins of the chambers tend to meander irregularly around the test, giving it something of an ornate appearance. Both molecular and structural evidence indicate that multi-chambered forams arose from ancestors with undivided tests on more than one occasion, and the majority of multi-chambered forams can be assigned to two major lineages (Pawlowski et al. 2013). In one lineage, the Globothalamea (which includes, for instance, the rotaliids), the basic chamber shape is globular with successive chambers in the test being wider than long. In the other lineage, the Tubothalamea (including the miliolids and spirillinids), the basic chamber shape is tubular, and the test may grow through a number of spirals before it even starts to be divided into chambers (if at all). Members of the two lineages with calcareous tests may also be distinguished by their test structure: in calcareous globothalameans, the crystals making up the test are arranged regularly so the overall appearance of the test is hyaline (glass-like). In contrast, tubothalameans have the crystals of the test arranged irregularly so the appearance of the test is porcelaneous (like porcelain). Meandropsinids are unmistakeably tubothalameans in both regards.

Like other large forams of the Mesozoic, meandropsinids did not make it past the end of the Cretaceous. Early Palaeocene taxa that have been included in the families represent distinct lineages that evolved to take their place, occupying the ecological spaces opened up by the mass extinction ending the era.

REFERENCES

Loeblich, A. R., Jr, & H. Tappan. 1964. Treatise on Invertebrate Paleontology pt C. Protista 2. Sarcodina: chiefly "thecamoebians" and Foraminiferida vol. 1. The Geological Society of America, and The University of Kansas Press.

Pawlowski, J., M. Holzmann & J. Tyszka. 2013. New supraordinal classification of Foraminifera: molecules meet morphology. Marine Micropalaeontology 100: 1–10.

Doe, it's Deer

Marsh deer Blastocerus dichotomus, copyright Jonathan Wilkins. An animal that just screams out, "Am I wearing the Chanel boots? Yes, I am."

I hardly need to explain what deer are, do I? Deers (Cervidae) are generally recognised as the second most diverse family of hoofed mammals (after bovids) in the modern fauna. Their most recognisable feature, of course, is the possession of antlers: bony cranial appendages that are shed and regrown every year rather than being permanently in place like the horns of a bovid. When antlers first grow, they are covered with a layer of skin (the velvet) that supplies them with blood, but this skin is later shed to expose the bare bone. In most species, antlers are only grown by males whose use them in conflicts during the mating season. The only genus of deer that grows antlers in both sexes is Rangifer, the reindeer. There is also one living species that lacks antlers, the Chinese water deer Hydropotes inermis; instead of antlers, males of this species possess large, dagger-like canines. In the majority of deer species, antlers are subcylindrical and often branched but broad palmate antlers have evolved on multiple occasions within the family. Antler morphology is generally significant in distinguishing taxa but it should be noted that variation within species is not unknown. For instance, the few recorded males of the small, now possibly extinct population of moose introduced to the south of New Zealand lacked the large palmate antlers generally associated with the species, probably due to poor nutritional conditions. Instead, they had more slender antlers that only became moderately palmate distally, like those of a fallow deer Dama dama.

One of the few photographs of moose from New Zealand, from here. I think this might be the one shot at Herrick Creek in 1952 but I could be wrong.

The first antlered deer are known from Europe back in the early Miocene, about 17 million years ago. They are not known from North America until some time later in the Pliocene, about five mya (Pitra et al. 2004), though these days they are every bit as diverse in the Americas as in Eurasia. They never made much inroad into Africa, only extending into the northernmost part of the continent, and they never made it into Australasia under their own steam, though a number of species have been dispersed to various parts of the world by humans. For instance, at least half a dozen species have become established in New Zealand, and until recently reindeer might be found wandering among penguin colonies in South Georgia.

Reindeer and king penguins on South Georgia, from here.

Recent decades have seen some pretty wild swings in cervid taxonomy, with the number of subfamilies recognised varying from two to seven, and some authors recognising a much larger number of genera and species than others. However, our general understanding of cervid interrelationships is pretty good these days, with many differences between systems being a question of ranking more than anything else. Recent studies have agreed that modern deer can be divided between two primary lineages that may be called the Cervinae and Capreolinae (Gilbert et al. 2006). The Cervinae include the majority of deer species in the Old World with a single species (the wapiti Cervus canadensis) extending its range into the New World. The remaining New World deer all belong to the Capreolinae, which also includes four genera (Rangifer, Hydropotes, the roe deer Capreolus and the moose Alces) found in Eurasia.

Male tufted deer Elaphodus cephalophus, copyright Heush.

The Cervinae can be divided between two tribes, the Muntiacini and Cervini. Muntiacini include the muntjaks of the genus Muntiacus and the tufted deer Elaphodus cephalophus. These are small deer native to southern and eastern Asia. Antlers are small and simple in all Muntiacini: muntjaks have antlers with only a single short anterior branch whereas the tufted deer has unbranched antlers that are barely visible under the large tuft of hair that this species has on top of the head. Muntiacini also resemble Hydropotes in their possession of large canines in the males. The other tribe, Cervini, includes larger deer species with more complex, multi-branched antlers. Some authors have historically placed all species of Cervini within a single genus Cervus; others may recognise nine distinct genera. Numbers of recognised species have also varied, largely due to phylogenetic studies finding that taxa previously recognised as conspecific subspecies may be more distantly related to each other or may not form monophyletic units. For instance, the wapiti has often been regarded as a subspecies of the red deer Cervus elaphus but recent studies have suggested that it is more closely related to the sika C. nippon and the white-lipped deer Przewalskium or Cervus albirostris, two east Asian species (Pitra et al. 2004). Difficulties in elucidating cervin phylogeny are probably best exemplified by the case of Père David's deer Elaphurus or Cervus davidianus, originally native to southern China but now only surviving in captivity. Molecular phylogenies associate this species closely with the brow-antlered deer Cervus eldi but it has many morphological features indicating a close relationship with C. elaphus, and it is widely suspected that Père David's deer originated from a hybridisation event between the two latter species.

Pudu (I think a northern pudu Pudu puda), copyright Neil McIntosh.

The Capreolinae can be divided between three main lineages. One comprises the roe deer and water deer; another comprises the moose (again, I'm making a point of referring to genera rather than species because the number of recognised species may differ between authors). Note that the position of the water deer suggests that the antler-less state of this species represents a secondary loss rather than retention of a primitive state. The majority of capreolines belong to the third lineage, commonly recognised as the tribe Odocoileini. Except for the reindeer, the species of this lineage are restricted to the New World, with the higher diversity in South America. The Odocoileini are perhaps the most taxonomically uncertain section of the deer family. There appears to be no question, at least, that Rangifer represents the sister group of all other Odocoileini. The remaining odocoileins have generally been divided between six genera: Odocoileus (including the mule deer O. hemionus and white-tailed deer O. virginianus), Mazama (brockets), Pudu (pudus), Hippocamelus (guemuls), the marsh deer Blastocerus dichotomus and the pampas deer Ozotoceros bezoarticus. However, except for the two monotypic genera, monophyly of all these taxa was placed in question by a recent molecular phylogenetic study of the group by Gutiérrez et al. (2017). The issue is particularly marked for the brockets, small deer with unbranched antlers, as not only the genus as a whole but also species within the genus have been indicated as non-monophyletic. Recent years have, as a result, seen something of a burst of new brocket species being described. It is quite probable that a similar taxonomic explosion may be in line for the genus Odocoileus, with both of the currently recognised species including a number of subspecies and each being of suspect monophyly. Matters are further complicated by the possibility of hybridisation between the two 'species'.

REFERENCES

Gilbert, C., A. Ropiquet & A. Hassanin. 2006. Mitochondrial and nuclear phylogenies of Cervidae (Mammalia, Ruminantia): systematics, morphology, and biogeography. Molecular Phylogenetics and Evolution 40 (1): 101–117.

Pitra, C., J. Fickel, E. Meijaard & P. C. Groves. 2004. Evolution and phylogeny of Old World deer. Molecular Phylogenetics and Evolution 33: 880–895.

Conus jaspideus or Conasprella jaspidea, Take Your Pick

Live Conasprella jaspidea, copyright Anne DuPont.

Cone shells are one of the classic varieties of tropical sea shells, perhaps only rivalled in their familiarity with the general public by cowries and conches. Over 800 species of the family Conidae have been described from around the world. The specimen above represents one of these species, going by the name of Conasprella jaspidea or Conus jaspideus. The alternatives reflect the conflict between those who would treat all cone shells as belonging to a single genus Conus, or those who would divide them between multiple genera (Conasprella jaspidea is the name used for this species by Puillandre et al., 2014). One 2009 classification went so far as to divide the cone shells between 89 genera in five separate families, which does seem perhaps a little excessive. Among other features, Conasprella species differ from Conus sensu stricto in having a higher spire to the shell.

The type specimen of Conasprella jaspidea, copyright MHNG.

Conasprella jaspidea is found in coastal sections of the western Atlantic between Florida and the area of Rio de Janeiro. It is a medium-sized shell, reaching about three centimetres in length. Whorls of the spire are marked by distinct shoulders, and the body whorl is ornamented by spiral cords. The colour of the shell is white, orange or brown with darker brownish or violet spots. Shells of C. jaspidea may vary in texture from granular to smooth. These variants were initially recognised as distinct species or subspecies Conus jaspideus and C. verrucosus but, not only can both forms be found intermixed within a single population, the difference between them may be simply a question of the degree of wear a shell has been exposed to (Santos Gomes 2011).

Like other cone shells, Conasprella jaspidea is venomous with the radula bearing a single functional tooth modified into a short of hypodermic needle for injecting venom. Species of Conasprella are vermivorous (that is, they feed on worms). Feeding by a live individual of C. jaspidea was observed in an aquarium by Santos Gomes (2011). Photographs therein show the individual ingesting a polychaete worm that was perhaps not too much shorter in length than the cone shell itself; the process of feeding (from the initial strike with the radula to completion of ingestion) took about eighteen minutes from start to finish.

REFERENCES

Puillandre, N., T. F. Duda, C. Meyer, B.M. Olivera & P. Bouchet. 2014. One, four or 100 genera? A new classification of the cone snails. Journal of Molluscan Studies 81: 1–23.

Santos Gomes, R. dos. 2011. Conus jaspideus (Mollusca: Neogastropoda: Conoidea) on the Brazilian coast. Journal of the Marine Biological Association of the United Kingdom 91 (2): 531–538.

Darklings, Tok Toks and Pie-dishes

False wireworm beetle Gonocephalum sp., copyright EBKauai.

It has been noted to the point of cliché that the Creator has an inordinate fondness of beetles. Even within the massive range of beetle diversity, though, certain families stand out as particularly diverse. One such family is the Tenebrionidae, with over twenty thousand known species worldwide. The family is sometimes referred to as the darkling beetles but no one vernacular name is really sufficient for this group. Not only are tenebrionids taxonomically diverse, they are morphologically diverse, varying from long-legged and elongate to hemi-spherical and robust, from smooth and shining to ornate and hairy, from dull-coloured and retiring to bright and striking. Habits vary from detritivorous to xylophagous (feeding on decaying wood) to herbivorous to mycetophagous, with even a few predators. Larvae of some species are of economic significance as pests: the false wireworms feed on the roots of crops or lawns, while mealworms and flour beetles attack stored products (mealworms are, of course, also used as pet food and occasionally even as human food). Several species live as inquilines of social insects such as ants or termites. The highest diversity of tenebrionids is in relatively arid regions; some species, such as the tok tok beetles of southern Africa and the pie-dish beetles of Australia, are familiar sights in such habitats.

Pie-dish beetle Helea sp., copyright Australian Museum.

With such high diversity, it is not easy to define this group without encountering exceptions, but generally tenebrionids have the antennae eleven-segmented and inserted below lateral expansions of the genae. The procoxal cavities are usually closed externally, and the legs of most species have a 5-5-4 tarsal formula. The first three sternites of the abdomen are fused (Kergoat et al. 2014). Several subfamilies are recognised, but they are commonly grouped into three clusters known as the lagrioid, pimelioid and tenebrionoid branches of the family (Matthews & Bouchard 2008). Many members of the lagrioid and tenebrionoid branches possess well-developed defensive glands in the abdomen. The rear sternites of the abdomen in these species are hinged on the sides rather than along the midline as in more primitive forms, allowing the abdomen to expand as the gland reservoirs fill with a repugnant fluid that can be expelled when required. Many larger tenebrionids have a tendency to walk with their rear ends tilted upwards, ready to unleash at a moment's notice.

Allecula rhenana, copyright Stanislav Krejčík.

Members of the pimelioid branch, including the subfamilies Pimeliinae and (possibly) Zolodininae, lack abdominal defensive glands. In many parts of the world, pimelioids are the dominant tenebrionids in dry habitats. The lagrioid branch includes the single subfamily Lagriinae, defined by features of the genitalia. Matthews & Bouchard (2008) also listed the small subfamily Phrenapatinae in this branch but a molecular phylogenetic analysis of the family by Kergoat et al. (2014) placed this latter subfamily in the tenebrionoid branch. The tenebrionoid branch also includes the Tenebrioninae, Diaperinae, Alleculinae and Stenochiinae, though monophyly of the Tenebrioninae and Diaperinae is uncertain (Kergoat et al. 2014). Diaperines include a number of shiny, sometimes strikingly coloured species; members of the tribe Leiochrinini look more like ladybeetles of the Coccinellidae than typical tenebrionids. The Tenebrioninae include such notable members as the false wireworms of the tribe Opatrini, the mealworms of the Tenebrionini and the flour beetles of the Triboliini. Finally, the Alleculinae are a distinctive group of often relatively soft-bodied tenebrionids readily distinguished from other members of the family by their pectinate claws; in some older classifications, alleculines were treated as a separate family of their own.

REFERENCES

Kergoat, G. J., L. Soldati, A.-L. Clamens, H. Jourdan, R. Jabbour-Zahab, G. Genson, P. Bouchard & F. L. Condamine. 2014. Higher level molecular phylogeny of darkling beetles (Coleoptera: Tenebrionidae). Systematic Entomology 39: 486–499.

Matthews, E. G., & P. Bouchard. 2008. Tenebrionid Beetles of Australia. Australian Biological Resources Study.