Flies are in the news this week because of a newly published paper demonstrating that male Drosophila flies who fail to find a mate are more likely to consume more alcohol. This finding is not only scientifically interesting, it probably resonates with at least a few members of our species. But, there’s much more to Diptera than just a lonely night at the bar! After a brief hiatus, the list is back. For your entomological entertainment, we present five more reasons that Diptera are an exceptionally interesting order (see reasons 1-5 here, and reasons 6-10 here)
11. Glow, little glowworm, glow. Mention “insect” and “ecotourism” in the same sentence and most people will connect those terms with a line drawn through butterflies. But one of the most famous examples of insect-fueled ecotourism owes its success to a fly. The predatory larvae of the keroplatid genus Arachnocampa have a delightful (well, not for their prey) method of hunting, in which they hang from the ceiling of a cave, drop a sticky silk thread and secrete bioluminescent droplets that run down the thread and glow in the dark. The light attracts prey and the thread captures them. A cave filled with Arachnocampa larvae can be a beautiful spectacle, and humans in New Zealand and Australia have capitalized on this piece of natural history by operating tours through the glow-worm caves. An unrelated species of fungus gnat in the genus Orfelia (with a different mechanism for generating bioluminescnece) is found in southeastern North America, where a cave in Alabama features tours to see the “dismalites”.
12. Strange lifestyles. Not all flies fly, not all flies even look like flies, and not all flies reproduce in the “usual” way. There is an enormous variety of alternative lifestyles in Diptera. Females of several species, across a range of families, reproduce parthenogenetically, producing eggs with no genetic contribution from a male. Some flies take this process one step further; some gall midges, such as Miastor metraloas, are both parthenogenetic and paedomorphic – larvae become sexually mature and start producing larvae before they even reach adulthood. Populations can build up incredibly quickly in such species. One of my students collected more than 18,000 Miastor metraloas from a single decaying log in one summer a few years ago. In contrast to the great fecundity of some of the gall midges, females in a few families (Glossinidae, Hippoboscidae, Streblidae and others) retain a developing larva inside their body until it is almost mature. This huge larva then pupates almost immediately after leaving the female’s body.
13. The CSI effect. Few entomological subjects have the morbid fascination of forensic entomology. Perhaps the idea that a handful of maggots can help solve a murder has a David-and-Goliath feel that many find satisfying. Blow flies (Calliphoridae) and flesh flies (Sarcophagidae) are remarkably adept at locating dead bodies, even when buried, and the developing larvae that the adult flies leave behind on this prized food source develop in a predictable way and at a predictable rate, making these maggots an excellent piece of evidence for establishing the time, and sometimes the circumstances, of death. With the frequent portrayal of entomologists in film and television as near-sighted nerds surrounded by displays of pinned butterflies, it’s appealing to see the awesome power that we can now bring to bear in courtroom dramas.
14. Bird feeders. No, not bird feeders in the sense of seeds in the backyard for our feathered friends. these “bird feeders” are Diptera that live their lives on birds or in their nests, feeding on the hosts or in the nest material. Many of these flies are rarely collected outside the cozy confines of the nest. Larval blow flies in the genus Protocalliphora are voracious blood feeders on nestlings, using their mouth hooks to attach and feed. In the family Hippoboscidae, it’s the adults we usually associate with birds – these flattened flies hang onto feathers with specially modified claws and ride around with their host, feeding on it as they go. Bird flies in the genus Carnus are scavengers in the nest material as larvae but when the adults emerge they tear off their own wings (or they break off) and then begin feeding on the blood of the nestlings. A few other acalyptrate flies are closely associated with bird nests, where they are apparently scavengers. Some genera, such as the heleomyzid Neossos, are almost never collected outside bird nests (but we’ve collected hundreds of specimens by searching through nest boxes).
15. Mimicry. Many flies bear a striking resemblance to stinging Hymenoptera. Multiple species in many families including Syrphidae, Bombyliidae, Oestridae, Asilidae and others can easily be mistaken for bumble bees, wasps, or other dangerous hyms on the wing or on a flower. Mimicry of this sort is probably a very useful anti-predator adaptation. This strategy also works remarkably well on science journalists and book publishers, who regularly use photos of syrphid flies in stories about bees. On the other hand, many of these bee-mimicking flies are very popular with insect collectors. Sometimes, mimicry can blow up in your face . . .
In the next installment – the Culture Edition, wherein we explore the role of flies in the arts and humanities.