Chapter 9 Biodiversity of Diptera Gregory W. Courtney1, Thomas Pape2, Jeffrey H. Skevington3, and Bradley J. Sinclair4 1 Department of Entomology, 432 Science II, Iowa State University, Ames, Iowa 50011 USA 2 Natural History Museum of Denmark, Zoological Museum, Universitetsparken 15, DK – 2100 Copenhagen Denmark 3 Agriculture and Agri-Food Canada, Canadian National Collection of Insects, Arachnids and Nematodes, K.W. Neatby Building, 960 Carling Avenue, Ottawa, Ontario K1A 0C6 Canada 4 Entomology – Ontario Plant Laboratories, Canadian Food Inspection Agency, K.W. Neatby Building, 960 Carling Avenue, Ottawa, Ontario K1A 0C6 Canada Insect Biodiversity: Science and Society, 1st edition. Edited by R. Foottit and P. Adler © 2009 Blackwell Publishing, ISBN 978-1-4051-5142-9 185 he Diptera, commonly called true flies or other organic materials that are liquified or can be two-winged flies, are a familiar group of dissolved or suspended in saliva or regurgitated fluid T insects that includes, among many others, (e.g., Calliphoridae, Micropezidae, and Muscidae). The black flies, fruit flies, horse flies, house flies, midges, adults of some groups are predaceous (e.g., Asilidae, and mosquitoes. The Diptera are among the most Empididae, and some Scathophagidae), whereas those diverse insect orders, with estimates of described of a few Diptera (e.g., Deuterophlebiidae and Oestridae) richness ranging from 120,000 to 150,000 species lack mouthparts completely, do not feed, and live for (Colless and McAlpine 1991, Schumann 1992, Brown onlyabrieftime. 2001, Merritt et al. 2003). Our world tally of more As holometabolous insects that undergo complete than 152,000 described species (Table 9.1) is based metamorphosis, the Diptera have a life cycle that primarily on figures extracted from the ‘BioSystematic includes a series of distinct stages or instars. A typi- Database of World Diptera’ (Evenhuis et al. 2007). cal life cycle consists of a brief egg stage (usually a few The Diptera are diverse not only in species richness, days or weeks, but sometimes much longer), three or but also in their structure (Fig. 9.1), habitat exploita- four larval instars (usually three in Brachycera, four in tion, life habits, and interactions with humankind lower Diptera, more in Simuliidae, Tabanidae, Thau- (Hennig 1973, McAlpine et al. 1981, 1987, Papp maleidae, and a few others), a pupal stage of varying and Darvas 2000, Brown 2001, Skevington and Dang length, and an adult stage lasting from less than 2 h 2002, Pape 2009). The Diptera have successfully (Deuterophlebiidae) to several weeks or even months. colonized all continents, including Antarctica, and The eggs of Diptera are laid singly, in small clusters, or practically every habitat except the open sea and in loose or compact masses, and they can be attached inside glaciers. Larval Diptera are legless (Figs. 9.2 and to rocks, vegetation, or other substrata, or deposited 9.3F-J) and found in a variety of terrestrial and aquatic on or in the food source. Oviposition sites are usu- habitats (Teskey 1976, Ferrar 1987, H¨ovemeyer ally in or near the larval habitat, which ensures that 2000, Courtney and Merritt 2008). Larvae of most eggs are placed in a location suitable for larval devel- species can be considered aquatic in the broadest opment, with a notable exception being the human sense because, for survival, they require a moist to wet bot fly, Dermatobia hominis, which glues its eggs to environment within the tissues of living plants, amid zoophilous dipterans (e.g., calyptrate flies and Culi- decaying organic materials, as parasites or parasitoids cidae), thereby ensuring a carrier-mediated infection of other animals, or in association with bodies of water. (Guimar˜aes and Papavero 1999). In some groups, eggs Most larvae are free-living and swim, crawl, or tunnel areincubatedandhatchduring(e.g.,Sarcophagidae)or actively in water (e.g., Chaoboridae, Chironomidae, immediately after deposition (e.g., many Tachinidae), Culicidae, and Simuliidae), sediments (e.g., Cerato- or the female is truly viviparous when the larvae are pogonidae, Psychodidae, Tabanidae, and Tipulidae), nourished and grow while still inside the female (e.g., wood (e.g., Axymyiidae, some Syrphidae and Hippoboscoidea, and mesembrinelline Calliphoridae) Tipulidae), fruit (e.g., Chloropidae and Tephritidae), or (Ferrar 1987, Meier et al. 1999). For a given species, decaying organic material (e.g., Ephydridae, Muscidae, all larval instars usually occur in the same habitat. Sarcophagidae, and Sphaeroceridae). Other larvae In general, the duration of the first instar is shortest, inhabit the tissues of living organisms (e.g., Acroceri- whereas that of the last instar is much longer, often dae, Oestridae, Pipunculidae, and Tachinidae). Still several weeks or even months. Although most Diptera others (e.g., larvae of the superfamily Hippoboscoidea) exhibit sexual reproduction, parthenogenesis occurs in are retained and nourished in the female abdomen some groups, and reproduction by immature stages until deposited and ready to quickly pupariate. Most of (paedogenesis) has been recorded in some gall midges the feeding and accumulation of biomass occurs in the (Cecidomyiidae). larval stage, and adult Diptera mostly take only what Among the most unusual life histories is that they need to supply their flight muscles with energy. of the Nymphomyiidae. Adults have a larviform Among those flies that feed extensively, their diets con- appearance, lack mouthparts (Fig. 9.3B), and possess sist of nectar or honeydew (e.g., Blephariceridae and wings that are deciduous, elongate, and fringed with Bombyliidae), pollen (e.g., Nemestrinidae and Syrphi- long microtrichia (Courtney 1994). Most species dae), vertebrate blood (e.g., Culicidae and Glossinidae), are associated with small headwater streams where insect hemolymph (e.g., some Ceratopogonidae), and larvae, pupae, and copulating adults occur on rocks Biodiversity of Diptera 187 covered with aquatic mosses. Although few details number of species in the Keroplatidae (Orfelia fultoni, about mating behavior are available, observations of Arachnocampa spp., and Keroplatus spp.) are biolumi- Appalachian species suggest that adults locate a mate nescent and emit a blue-green light as larvae. These soon after emergence, couple, descend into the water glowworms construct mucous tubes from which they in copula, shed their wings, and crawl to an oviposition hang snares with droplets of oxalic acid that capture site. The female then lays a rosette of eggs around the and kill prey attracted by their bioluminescence. The coupled adults, which die in copula (Courtney 1994). larvae are voracious predators and feed on many types Another remarkable life history is that of Fergusonina of arthropods attracted to their glow (Baker 2002). In turneri (Fergusoninidae), which in an obligate mutu- some instances, these glowworms congregate in large alism with the nematode Fergusobia quinquenerviae is numbers and form impressive displays. For example, a gall building on the myrtacean plant Melaleuca quin- superb concentration of Arachnocampa luminosa in the quenervia (Taylor 2004). Galls are initiated in buds and Waitoma Caves in New Zealand attracts more than young leaves by juvenile nematodes, which are injected 300,000 visitors per year (Baker 2002). by ovipositing female flies, along with their own eggs. A common mating behavior among the lower When the fly eggs hatch, the larvae form individual Diptera (Chaoboridae, Chironomidae, and others) cavities in the galls, and nematodes move into these is the formation of dense and sometimes enormous and coexist with the fly larva. The nematodes pass swarms (Vockeroth 2002). The swarms generally are through at least one parthenogenetic generation, and composed of males, and when females enter the swarm, fertilized female nematodes of a later sexual generation coupling quickly takes place. Males often exhibit invade the late third-instar fly larva. Nematode eggs are adaptations that enable mate detection. For example, deposited in the larval hemolymph and, after hatching, the eyes of males of most species engaged in swarming the juvenile nematodes migrate to the fly ovaries. When are enlarged and contiguous above (presumably to the adult female fly hatches, it will continue the cycle aid in spotting females from below) and the antennae by depositing new nematodes along with its own eggs. have numerous, long, hairlike setae that allow them In the Phoridae, the peculiarly swollen, physogastric to detect a female’s wing beats. In the Brachycera, females of species in the subfamily Termitoxeniinae, premating behavior includes posturing and displays which are all associated with fungus-growing termites, in courtship that can become complex performances show a post-metamorphic growth in both head and with combinations of kneeling, jumping, and flapping hind legs, which is unique for an adult, nonmolt- (e.g., Struwe 2005). In dance flies (Empididae), which ing insect (Disney and Kistner 1995). These termite often have mating swarms, the male presents the inquilines were described by Wasmann (1910: 38) as female with an edible lure or an inedible substitute to ‘a store-house of anomalies, whether we consider them initiate mating (Cumming 1994). from the point of view of morphologists, anatomists, Many Diptera congregate at landmarks for the pur- evolutionists, or biologists. They are exceptions to the pose of mating. Landmarks can range from a rock to laws of entomology’. a tuft of grass, a road, a stream