Graptomyza triangulifera Bigot (Diptera: Syrphidae)
This week’s insect is Graptomyza triangulifera Bigot (Diptera: Syrphidae) a member of the group commonly known as flower flies (or hover flies). Graptomyza is an old-world genus, absent from the Americas. There are 92 species worldwide with 20 reported from the Afrotropical region. Little is known about the habits of members of this genus, but zig-zag flight behaviour has been documented in Graptomyza species, where an individual flies rapidly in one direction, stops and hovers in place and then speeds off in another direction, perhaps confusing avian predators. Members of the genus are easy to recognize with their head prolonged into a snout, their scutellum (the last structure of the thorax) with a central pit, and the eyes of the males dichoptic (= separated), in contrast to most other hover flies where the eyes of males are holoptic (= joined). Graptomyza adults feed on pollen and nectar (accessing the latter perhaps aided by their snout-like head). Feeding behaviour of larval Graptoymza is saprophytic, larvae feeding on rotting plants and, sometimes, organic waste. In our project on insects associated with the wild fruits of Kenya we reared Graptomyza triangulifera from the rotting fruits of Strychnos madagascariensis, Tabernaemontana pachysiphon, Momordica foetida and Saba comorensis, all of which bear large fruits associated with forests. These four host fruits represent three families of flowering plants. Clearly, G. triangulifera is a generalist feeder.
Note: The full name of all species is a trinomial and includes the name of the person who described it, in our case Jacques-Marie-Frangile Bigot, a French entomologist who studied and described many Diptera species, especially Syrphidae. Note that unlike the first two parts of a species’ name (genus and species epithet) the name of the describer is not italicized.
Credits: Dr Robert Copeland