T.E.R:R.A.I.N - Taranaki Educational Resource: Research, Analysis and Information Network


Fly (Hover, Drone fly) Eristalis tenax

Kingdom: Animalia
Phylum: Arthropoda
Class: Insecta
Order: Diptera
Family: Syrphidae
Genus: Eristalis
Subgenus: Eoseristalis
Species: E. tenax
Binomial name: Eristalis tenax
Synonyms: Eristalis campestris, Musca tenax 
Common name: Dronefly, Drone Fly

Eristalis tenax is a European hoverfly). It has been introduced into New Zealand and is widely established. This large stock fly can reach a body length of 14 to 18 mm and a wingspan 15mm. It has a dark brown abdomen, the second segment of which has yellow, reddish-yellow or ochre wedge-shaped spots. The drone fly has black compound eyes, which are connected by hairy bends above and below. The females’ eyes are clearly separated, while the males meet. They mimic bees and feed on honey and pollen and hence are beneficial pollinators of flowers. Males have hovering displays. 
The larva of E. tenax is a rat-tailed maggot. It lives in drainage ditches, pools around manure piles, sewage, and similar places containing water badly polluted with organic matter. The larva likely feeds on the abundant bacteria living in these places. When fully grown, the larva creeps out into drier habitats and seeks a suitable place to pupate. In doing so it sometimes enters buildings, especially barns and basements on farms. The pupa is 10–12 mm long, grey-brown, oval, and retains the long tail; it looks like a tiny mouse. 
The adult fly that emerges from the pupa is harmless. It looks somewhat like a drone honey bee and likely gains some degree of protection from this resemblance to a stinging insect. The adults are called drone flies because of this resemblance. Like other hoverflies, they are common visitors to flowers, especially in late summer and autumn. Adult drone flies are active during the summer months and the female drone also flies over winter.

A female Eristalis tenax. The females’ eyes are clearly separated,
 

A male Eristalis tenax. The male's eyes meet.  

Female

Head of a female 


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