Insect of the week (31): A delicate killer; Hemerodromia sp. (Diptera: Empididae: Hemerodromiinae)
Our species this week is a sleek member of the genus Hemerodromia. Unlike many of our previous subjects, this genus is relatively speciose with at least 170 species known globally. They first appear in the fossil record (in amber collected in present day Ukraine) during the Priabonian age of the early Eocene, between 37.7 and 33.9 MYA. While the species doesn’t generate the excitement of collecting a rare or undescribed species, they make up for this with their intriguingly streamlined head and body shape and their bone-like, long, slender legs. Adults of Hemerodromia are predaceous but do not attack prey in flight. Rather they are often seen running quickly (the genus name is from the Greek meaning a “courier who runs for a whole day”) on vegetation and other substrates where they attack small prey with their sharp mouthparts. The wing venation of Hemerodromia is reduced compared with most Empididae making them poor fliers, and successful hunting appears to depend on their strong running ability and the heavily toothed raptorial forelegs with which they capture prey. The forelegs resemble those of Mantidae and some families of Neuroptera, particularly Mantispidae and Berothidae. This is a nice example of convergent evolution among disparate groups of predaceous insects. Adult Hemerodromia favour riparian habitats and are usually found close to the stream or river where their aquatic larvae develop. Like the adults, larvae are also predaceous, feeding on small invertebrates. They are known to attack blackflies (Simulidae), the sole vector of human onchocerciasis (River blindness), and may have some effect on limiting the transmission of the disease.
Credits: Dr Robert Copeland