The Stilt Bug Neides tipularius

Image copyright Janet Graham.

This is Neides tipularius, a widespread bug in the western part of the Palaearctic region. It feeds on a wide range of plants: I've seen references to it on grasses, on composites, or on chickweeds. It prefers drier regions such as coastal dunes or heaths.

Neides tipularius is a fairly typical member of the stilt bug family Berytidae. Berytids are more or less slender bugs in general but Neides is one of the more slender and long-legged ones. There are few other bugs with which a berytid could be confused; not only is there the wispy legginess to mark them, but berytids have distinctive long antennae with a short, spindle-shaped terminal segment forming a dark bobble at the end. Latreille (1802) did place N. tipularius in the genus Ploiaria, but that is now used for a group of small, long-legged assassin bugs with raptorial forelegs for catching prey.

Image copyright Sanja565658.

As with many other bugs, Neides tipularius exhibits polymorphism in wing development with flightless brachypters having narrower wings that only just reach the tip of the abdomen. Whether a given individual grows into a flying or flightless adult appears to be connected to the conditions under which they develop. Hot springs and summers have been noted to lead to increased numbers of macropterous adults.

REFERENCE

Latreille, P. A. 1802. Histoire Naturelle, générale et particulière des crustacés et des insectes vol. 3. Familles naturelles des genres. F. Dufart: Paris.

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.

Hoppers

The world is home to a wide variety of leafhoppers, both in terms of number of species and range of morphological disparity. One of the more diverse leafhopper families is the Delphacidae, including over two thousand species from around the globe. Delphacids are relatively small leafhoppers that are easily distinguished from other families by the possession of a large movable spur at the end of the tibia of the hind leg. I can't say as I know what the function of this spur is, but similar structures in other insect groups may be used for grooming.

Brown leafhoppers Nilaparvata lugens, from ICAR. The individual on the right is a long-winged disperser, the one on the left is a flightless brachypter.

Delphacids feed on the phloem of their host plants; the greater number of species are associated with monocots such as grasses. A number of species are significant economic pests; perhaps the most infamous are the brown leafhopper Nilaparvata lugens and white-backed leafhopper Sogatella furcifera which attack rice. They feed at the base of rice plants, causing the formation of round, yellow patches that soon dry up and turn brown, a condition known as 'hopper burn'. Death of the entire plant will often follow. As well as the direct damage from feeding, these leafhopper species also transmit viruses that further impact yields. Historically, numerous famines have been blamed on leafhopper outbreaks, such as the Kyoho famine of 1732 that saw rice production reduced to only 10% of its previous level. Estimates of the number of people affected by the famine seem to vary widely—according to Wikipedia, the official death toll was a bit more than twelve thousand people, but estimates of the actual number of fatalities range well in excess of 150,000. In more recent years, leafhopper outbreaks may be exacerbated by indiscriminate fertiliser and pesticide use, with the latter reducing competition for the hoppers from other insects or predators.

Delphacids (and many other leafhoppers) commonly exhibit polymorphism in wing development with both flying macropterous and flightless brachypterous forms occuring in a single population. The question of macroptery vs brachyptery is an environmental one. If a developing delphacid receives sufficient nitrogen then it will develop into a flightless adult, remaining in the place of its birth to continue to benefit from the good feeding conditions there. But if feeding conditions become degraded and the developing nymph is deprived of nitrogen then it will develop into a fully-winged adult that can leave its home in search of more favourable conditions elsewhere. Because of their small size, migrating delphacids may be carried long distances by the winds. In the case of pest species, this phenomenon of migration further exacerbates the problem of control as hopper populations from different countries are regularly mixed, increasing genetic diversity and resistance to varying control methods.

REFERENCE

Urban, J. M., C. R. Bartlett & J. R. Cryan. 2010. Evolution of Delphacidae (Hemiptera: Fulgoroidea): combined-evidence phylogenetics reveals importance of grass host shifts. Systematic Entomology 35: 678–691.

Edible Stinkbugs

In recent years, there has been some discussion in certain circles about whether people in western cultures should become more accepting of the practice of entomophagy: that is, eating bugs. For the most part, insects do not play a big part in diets in the English-speaking world except indirectly. In other parts of the world, however, certain insects may be eaten with relish. One such insect is the edible stinkbug Encosternum delegorguei of southern Africa.

Edible stinkbug Encosternum delegorguei, from Dzerefos et al. (2013).

The edible stinkbug is a member of the family Tessaratomidae, one of a number of families in the stinkbug superfamily Pentatomoidea. Tessaratomids are mostly relatively large, flat-bodied stinkbugs, often with shining metallic coloration, found in warmer parts of the world. They are all plant-suckers; one species, the lychee stinkbug Tessaratoma javanica, is a significant pest of lychee crops while the bronze orange bug Musgraveia sulciventris is a pest of citrus trees in Australia. The edible stinkbug feeds on a range of tree species, belonging to a number of different flowering plant families such as Combretaceae, Fabaceae and Ebenaceae. Though widespread in southern Africa, their distribution seems to be patchy; only certain ethnicities have a tradition of stinkbug harvesting (Dzerefos et al. 2013).

Harvester collecting stinkbugs, copyright Cathy Dzerefos.

Edible stinkbugs are collected during winter (the dry season) when they aggregate in large protective clusters (up to football-sized) on particular trees. Like other stinkbugs, Encosternum delegorguei produce a foul-smelling defensive chemical from glands on the thorax. As well as smelling bad, this chemical can stain skin and may cause temporary blindness if it gets into eyes. Dzerefos et al. (2013) note that stinkbug harvesters informed them that exposure to the defensive chemical over several years could cause fingernail loss and wart growth. The chemical needs to be removed from the bugs before they are cooked for consumption because, as one harvester explained, "if you eat the unprepared one it will kill taste for a month".

Clusters of stinkbugs are collected live into bags which are then shaken to encourage the bugs to discharge their chemicals. Further processing could be done by two methods. Perhaps the more common method is to pinch off the head of each bug then squeeze out the contents of the thorax, after which the bugs are cooked immediately. However, the Bolobedu people (who collect stinkbugs more for commercial sale than for their own consumption) place the bugs into a bucket with a perforated base, then pour hot water over them and stir vigorously. The bugs discharge their glands into the water as the heat kills them. They are then rinsed off in cold water, then returned to hot water for about eight minutes, then spread out on bags on the ground to dry. Any bugs that had not fully discharged their glands before dying can be recognised by dark marks on the thorax and are discarded. Though slightly more involved than the waterless method, this process of preparation has the advantage that bugs can be stored for some time rather than having to be cooked immediately. Stinkbugs are usually cooked by braising in a frying pan with salt; they are supposed to have a spicy taste, like chili.

Basket of prepared stinkbugs, from here.

According to Dzerefos et al. (2013), many of the stinkbug harvesters they spoke to reported a decline in populations of the bugs in recent years. Potential reasons for the decline included drought and/or the felling of trees that would otherwise be used by the bugs as roosts. Could edible stinkbugs be more widely used commercially? Perhaps, but it should be noted that while some groups relish the bugs, their neighbours disdain the delicacy. Mind you, Bolobedu people apparently didn't eat the bugs themselves before the 1980s, only taking up harvesting them when co-workers in tea plantations taught them what a resource they had on their hands!

REFERENCE

Dzerefos, C. M., E. T. F. Witkowski & R. Toms. 2013. Comparative ethnoentomology of edible stinkbugs in southern Africa and sustainable management considerations. Journal of Ethnobiology and Ethnomedicine 9: 20.

The Polyctenidae: Blood-sucking Bugs on Bats

Dorsal, ventral and lateral views of Eoctenes spasmae, from Marshall (1982).

If you ever feel inclined to scan through host records for ectoparasites (and really, why wouldn't you?), you may be struck by the impression that bats seem to be peculiarly lousy animals. There seems to be an unexpected number of groups of ectoparasites that have their highest number of species on bats. One possible reason for this is that, with over 900 potential host species, bat-parasite diversity is high simply because bat diversity is high. Nevertheless, there are other features peculiar to bats that make them excellent parasite hosts. The modification of their fore-legs into wings means that their ability to groom themselves is curtailed. Because many bat species roost in dense colonies, transmission of parasites from one bat to another may happen freely. And because most bats will consistently return to the same roost, speciation is promoted by each colony becoming like an isolated island.

At the same time, referring to bats as 'lousy' is misleading because one ectoparasite group that is curiously absent from bats is the true lice (why this should be I have no idea). Instead, bats are often host to a number of parasite groups all of their own. One such group is the Polyctenidae, flightless true bugs that are found only on bats in tropical and subtropical parts of the world. Polyctenids are closely related to the bed bugs of the Cimicidae and are not dissimilar in appearance. Noticeable differences are their relatively shorter antennae and absence of eyes. They also possess a number of bristle combs at various places on the body, roughly similar in appearance to those on fleas. Their front legs are short and have sucker-like structures on the tarsi instead of claws; the hind two pairs of legs are longer and clawed. The manner of movement of the legs is specialised for crawling among the hair of their host; if removed from the host, the bug is unable to move on a flat surface. Transmission of bugs from one host to another presumably happens only through direct physical contact. Polyctenids share with bed bugs the notorious practice of traumatic insemination with each male injecting sperm directly into the female's body cavity via sharpened genitalia. However, unlike bed bugs they are viviparous, producing live nymphs instead of eggs. The developing embryos are nourished by a 'pseudoplacenta' with a single female potentially containing several developing embryos in a conveyor arrangement at different stages of development. The most mature of these embryos protrudes from the female's genital opening for some time prior to birth and may be a third of its mother's size when born (Marshall 1982).

Type specimen of Hesperoctenes giganteus, from here.

Five genera of polyctenids are generally recognised, with four genera found in the Old World and only a single genus, Hesperoctenes, in the New World (Maa 1964; Ueshima 1972). A second New World genus, Parahesperoctenes, was described in 1947 from a single female, but as the features supposedly distinguishing it from Hesperoctenes related to the consistent duplication of combs, etc., it is thought likely that this was an ordinary individual of Hesperoctenes on the cusp of moulting from a nymph to an adult (so the features of the adult cuticle were visible through the translucent nymphal cuticle). Most of the polyctenid species have a restricted host range, being found on only a single bat species or a small number of closely related species. Some species of Hesperoctenes are more flexible, being found on a range of host species. Hesperoctenes and the Old World genus Hypoctenes are found on free-tailed bats of the Molossidae. Of the other Old World genera, Adroctenes is found on horseshoe bats and leaf-nosed bats of the Rhinolophidae and Hipposideridae, Polyctenes is found on ghost bats of the Megadermatidae, and Eoctenes is found on Megadermatidae, Nycterididae and Emballonuridae. Records of polyctenids from other bat families are currently regarded as suspicious, due to either mislabelling or cross-contamination. Ueshima (1972) suggested that records of Hesperoctenes fumarius from the bulldog bat Noctilio labialis might result from bugs being transferred while the bulldog bats were sharing a roost with their more usual molossid hosts.

Relationships between the genera were discussed by Maa (1964) who divided the family between two subfamilies on the basis of comparative features; a formal phylogenetic analysis of the family appears to still be wanting. On the basis of Hesperoctenes being the 'most specialised' genus and its shared host family with Adroctenes, Maa suggested an Old World origin for Polyctenidae. Eoctenes, with its broad host family range, was regarded as 'least specialised' and likely to be evolutionarily older than other genera. Many of the features distinguishing the polyctenid genera relate to the arrangement of combs: which combs are present where and how they are developed. Prior to Maa's revision, Hesperoctenes had been regarded as likely to be primitive within the Polyctenidae due to its relatively low number of combs. The mid- and hind legs of Adroctenes are fairly short compared to those of other genera.

REFERENCES

Maa, T. C. 1964. A review of the Old World Polyctenidae (Hemiptera: Cimicoidea). Pacific Insects 6 (3): 494–516.

Marshall, A. G. 1982. The ecology of the bat ectoparasite Eoctenes spasmae (Hemiptera: Polyctenidae) in Malaysia. Biotropica 14 (1): 50–55.

Ueshima, N. 1972. New World Polyctenidae (Hemiptera), with special reference to Venezuelan species. Brigham Young University Science Bulletin, Biological Series 17 (1): 13–21.

The Overall Scale

Scale insects have been the subjects of posts here twice before: in the first, I described their remarkable development, and in the second, I referred to the unusual genetics of some species. An appropriate next subject would, I suppose, be some of the ecological connections between scales and other animals.

Cochineal insects Dactylopius coccus on prickly pear, photographed by Joan Mundani.

Which starts, of course, with connections between scales and ourselves. Many scales are known as agricultural and horticultural pests, such as the red scale Aonidiella aurantii that attacks citrus. However, some scale species are not only welcomed but even deliberately cultivated due to commercial usage of the resins that they secrete. The two most significant commercial scales are the cochineal insects of the genus Dactylopius and the lac insect Kerria lacca. Other scale insects have also been used to produce similar products to those extracted from these species. Cochineal insects live on prickly pears, and produce carminic acid to ward off insect predators (though one predator, the caterpillar Laetilia coccidovora, is not only immune to the acid but stores it up to regurtitate at its own predators: Grimaldi & Engel 2005). Humans, on the other hand, are undeterred by carminic acid. The insects are collected, crushed, and the carminic acid extracted to produce the red dye cochineal, used (among other things) to give colour to food, or to dye fabric. It was an ill-fated attempt to establish a cochineal industry in Queensland that lead to the introduction of prickly pears to Australia: the plague-proportion spread of the prickly pears and their subsequent control by the moth Cactoblastis cactorum has become one of the textbook examples of biological pest control.

Branch covered with sticklac, produced by lac insects Kerria lacca, photographed by Jeffrey W. Lotz.

Lac insects produce a hard resinous shell for protection that, again, is their undoing in the eyes of humans. Sticklac, the twigs of trees covered by lac bugs, is harvested, then heated in canvas tubes. The resin melts and runs out through the canvas, leaving the wood and remaining insect parts behind. The resin is then processed to make the lacquer shellac. As a varnish, shellac has been mostly superseded by synthetic products, though it still has its afficionados. It is also used in the food industry to produce a shiny coating for confectionary or fruit.

Mating pair of the ant Acropyga epedana, photographed by Alex Wild. The queen is carrying the mealybug which while found the stockline for her new colony.

The use of scale products by humans has a long history. The Indian epic Mahabharata, believed written about the 8th century BC, describes the Lakshagriha, a highly flammable palace built by the Kaurava family out of shellac, jute and ghee in which they hoped to trap their enemies of the Pandava family (the Pandavas escaped through a tunnel when the palace burnt after having been warned by their uncle, though one wonders if the smell of ghee in the walls might have also aroused their suspicions). However, ants have been exploiting scale products for at least 40 million years, and probably much longer. Ants (like many other animals) are interested in scales for their honeydew, the excreted sugary waste from their sap diet. Ants not only collect the honeydew, they protect the scales from other insects and may carry them to fresher growth or more protected sites. Ants of the genus Acropyga are so dependent on mealybugs, waxy scale insects of the family Pseudococcidae, that when a young queen leaves her parent nest to mate, she will carry a mealybug with her so that her new colony can maintain its own stock. She even mates while holding on to it, as seen in the photo above. Acropyga queens have even been found preserved in Dominican amber, still carrying their mealybugs (Grimaldi & Engel 2005).

REFERENCE

Grimaldi, D., & M. S. Engel. 2005. Evolution of the Insects. Cambridge University Press.

Soft yet Scaly (Taxon of the Week: Coccidae)

The stellate scale Vinsonia stellifera (Coccidae). Scales are insects that have abandoned motility for most of their lives to become sedentary plant suckers. Photo from here.

The truly bizarre insects known as scales have been covered at this site previously, including a brief description of the scale life cycle. In that post I referred to the ensign scales or Ortheziidae; in this post I'll cover the soft scales or Coccidae. The Coccidae include about 1000 species, some of which produce a dorsal covering of wax while others lack a dorsal covering (Williams, 1991). While ortheziids belong to the group of scale families known as archaeococcids, coccids belong to the more derived grouping known as neococcids. Neococcids are distinguished from archaeococcids by the absence of spiracles on the abdomen, and of compound eyes in the adult males (instead, male neococcid eyes have become reduced to dissociated ocelli). Coccids are distinguished from other neococcid families by the presence of a pair of rounded or triangular plates at the base of the anal cleft (Williams, 1991).


While female scales remain immotile for the rest of their lives once they have found a host, males regrow their legs and usually develop wings at maturity to find females. This is the Kuno scale Eulecanium kunoense. Photo by Joyce Gross (and very impressive it is too - photographing something as minute as a male scale would not be an easy call.

Another distinctive feature of neococcids is something referred to as Paternal Genome Loss (PGL - also known as Paternal Genome Elimination). In most neococcid families, males are technically diploid but early in development the chromosomes a male has inherited from its father are all inactivated so that it becomes functionally haploid. When the male produces sperm, these inactivated chromosomes are eliminated from sperm production and only the maternally-inherited chromosomes are passed on to its offspring. The reason for the evolution of PGL remains unknown*, but it appears likely to have evolved among neococcids on a single occasion (Yokogawa & Yahara, 2009). True haplodiploidy as found in Hymenoptera, where males are truly haploid as opposed to functionally haploid, has also evolved in scales of the archaeococcid family Margarodidae but is as yet unknown among neococcids despite suggestions that PGL may be a precursor to the origin of haplodiploidy. It is worth noting that, while an origin of haplodiploidy from PGL may seem reasonably intuitive, there is the small problem that there are more than twice as many known cases of taxa evolving haplodiploidy as PGL.

*Endosymbiotic bacteria such as Wolbachia have been shown to cause PGL in some insects (and the presence or absence of endosymbionts has been shown to affect PGL in at least one neococcid); alternatively, it could result from genetic factors on the animal's own X chromosome promoting the transmission of maternal chromosomes.

REFERENCES

Williams, D. J. 1991. Superfamily Coccoidea. In The Insects of Australia, 2nd ed. vol. I pp. 457-464. Melbourne University Press.

Yokogawa, T., & T. Yahara. 2009. Mitochondrial phylogeny certified PGL (Paternal Genome Loss) is of single origin and haplodiploidy sensu stricto (arrhenotoky) did not evolve from PGL in the scale insects (Hemiptera: Coccoidea). Genes Genet. Syst. 84: 57-66.

Soft Waxy Scales

Nettle ensign scale (Orthezia urticae). Photo by Pavel Krásenský.

The Hemiptera (true bugs) are one of the definite contenders for the insect order containing the most oddballs (Coleoptera and Hymenoptera are probably their competitors). Hemiptera are well marked as a group by their specialised sucking mouthparts, but within the Hemiptera a wide range of body plans have arisen. The scale insects (Coccinea) are perhaps one of the oddest groups of all, and it is one of the scale families, the Ortheziidae, that is our current Taxon of the Week.

Scale insects get their name from the adult females, which have completely abandoned the joys of mobility and live their lives on a single spot, sucking the sap from a host plant. To protect themselves they secrete a covering of sticky wax or a hardened scale. Because of their sedentary lifestyle, indulgences such as legs or eyes are unnecessary, and have become reduced or lost. Only close inspection of the adult, or of the males or nymphs, would identify these creatures as even being insects. Those scales that are significant to humans are mostly plant pests, though some species are used to produce lacquer or the red dye known as cochineal (yep, gramophone records were once made from crushed insects).


Orthezia insignis female with crawlers emerging from the ovisac. Photo from here.

Scales of both sexes first hatch out of their eggs as highly mobile nymphs called 'crawlers', with fully developed legs and antennae (Williams, 1991). This is the dispersal phase of their life cycle - not only can they crawl around, but they are also small enough to be easily blown by the wind. Once they find a suitable host plant and moult to the next instar, scale nymphs become pretty much immobile, and lose all the paraphernalia of their youth. While females pretty much remain in this state for the rest of their life, males do things quite differently. They feed for the second and third instars, then enter a non-feeding pupal stage before emerging as the winged adult (the adult males of a few species lack wings). Adult male scales also don't feed and lack mouthparts - they will only live for a short time while they find a mate. Male scales are also one of the few groups of winged insects, in addition to Diptera (flies) and Strepsiptera, to have lost one of the pairs of wings (the first time I ever saw one, I was not yet aware of this and it confused me immensely). Because of their brief lifespan, male scales are relatively rare overall, though I get the impression that they can appear in large numbers in the right season. However, they are also of microscopic size, so are not likely to be noticed.


Male Orthezia insignis. Photo from here.

Scale insects are divided between a number of families. They are often divided into two superfamilies, the Orthezioidea (archaeococcids) and Coccoidea (neococcids) (Koteja, 2000), though other authors combine them all into the Coccoidea. However, the archaeococcids are united only by primitive characters and are assumed to be paraphyletic and ancestral to neococcids. The Ortheziidae (ensign scales) is one of the most basal of the families of Coccinea, and one of the earliest families known from the fossil record, in the Lower Cretaceous (Koteja, 2000) - however, the Coccinea fossil record is extremely poor and should be treated with caution (most female scales are distinguished by microscopic characters not usually preserved in fossils, and the great difference between males and females makes them impossible to identify with each other unless specimens are preserved in the process of mating). Characters giving away the basal position of ortheziids include the presence of abdominal spiracles in the female (lost in neococcids), and compound eyes in the male (in neococcids the compound eye has disintegrated into a row of separate simple eyes). Nymphs and adult females secrete symmetrical plates of wax on their backs, while the female also secretes a wax ovisac at the end of the abdomen in which she incubates her eggs. This is the 'ensign' referred to in the common name.

The Ortheziidae are not a particularly large family by insect standards - about 200 species are known. As with other scales, a number of species have been spread around the world along with infected host plants, and some can cause trouble as pest species.

REFERENCES

Koteja, J. 2000. Advances in the study of fossil coccids (Hemiptera: Coccinea). Polskie Pismo Entomologiczne 69: 187-218.

Williams, D. J. 1991. Superfamily Coccoidea. In The Insects of Australia, 2nd ed. vol. I pp. 457-464. Melbourne University Press.

Love Hurts

People generally know distressingly little about insects. The gossip section of the weekly telly guide with the paper on Saturday mentioned a comment by Jerry Seinfeld on an upcoming movie of his featuring bees: "Other insects are just kind of crawling around. They don't have the sophistication of the bee. They have no crime, they have no drugs, they have no rape. A little rape, but it's not that bad." Leaving aside the question of the propriety of these comments, I have one word to say about their accuracy: bedbugs. Welcome to the world of Traumatic Insemination.

Male bedbugs (Cimicidae) have a sharpened intromittent organ (or if you prefer, a great spike on their knob). The usual means of entry is ignored in mating - rather, the female genital tract is only used in egg-laying (Stutt & Siva-Jothy, 2001). Instead, the male uses his sharpened organ to pierce through the female's body wall and inject semen directly into the body cavity.

Males and females do not always have the same aims in sexual reproduction. Because the limits on reproduction rates for males are relatively minimal, it is generally in the interest of males to maximise their insemination rate, in order to maximise the number of offspring they produce. Females, on the other hand, are more likely to have a maximum reproductive rate limited by the number of offspring they can safely produce in a given time period. Therefore, it is more advantageous for them to limit fertilisation to the best males to maximise the health of their offspring. As well as the obvious restrictions a female can place on fertilisation by limiting the ability of males to mate with her, the genital tract of females often has adaptations to 'test' sperm. The genital tract itself may be hostile to sperm survival (by being highly acidic, for instance). There may be structures such as a bursa copulatrix that store and/or digest sperm, limiting their access to further parts of the tract.

It is suspected that traumatic insemination evolved in males to bypass these restrictions on the part of the females. A good demonstration of this is seen in bugs of the family Nabidae, where entry into the female is still by the genital tract, but the sharpened intromittent organ pierces the wall of the bursa copulatrix (Tatarnic et al., 2006). Experimental evidence has shown that in traumatic inseminations the fertilisation advantage is held by the last males to mate with a female (Stutt & Siva-Jothy, 2001).

Nevertheless, females are not without defenses. While female bedbugs show a surprising lack of behavioural defenses against mating, they have developed an entirely novel paragenital system called the spermalege. In the common bedbug (Cimex lectularius), the external part of the spermalege is a special notch and a thickened part of the cuticle. Internally, there is a pocket filled with cells that receives the male ejaculate. Morrow & Arnqvist (2003) demonstrated that traumatic insemination through the spermalege had relatively little effect on the health of the recipient females. However, if the body wall was pierced anywhere else the female's survival rate was severely compromised. The internal part of the spermalege probably fulfils the sperm-killing role of the usual genital tract, as well as reducing the direct exposure of the female body cavity to potentially harmful ejaculate (Morrow & Arnqvist, 2003).

Different genera of bedbugs show a wide range of variation in the complexity of the paragenital system, from species entirely lacking one to species in which the system is exceedingly complex. In at least one genus, Afrocimex, a spermalege is present in both males and females (Tatarnic et al., 2006). It has been suggested that the presence of a spermalege in males defends against damage from homosexual matings - male bedbugs apparently tending to stab first and check suitability afterwards.

REFERENCES

Morrow, E. H., & G. Arnqvist. 2003. Costly traumatic insemination and a female counter-measure in bed bugs. Proceedings of the Royal Society of London Series B - Biological Sciences 270: 2377-2381.

Stutt, A. D., & M. T. Siva-Jothy. 2001. Traumatic insemination and sexual conflict in the bed bug Cimex lectularius. Proceedings of the National Academy of Sciences of the USA 98 (10): 5683-5687.

Tatarnic, N. J., G. Cassis & D. F. Hochuli. 2006. Traumatic insemination in the plant bug genus Coridromius Signoret (Heteroptera: Miridae). Biology Letters 2: 58-61.