Compost Fly
Male
Adelaide Hills
Compost Fly
Male twisting more
 
                      
Compost Fly (Bibio imitator)Class: Animals (Animalia) - Jointed Legs (Arthropoda) - Insects (Insecta)
Order: Flies (Diptera)
Family: March Fly (Bibionidae)     iNaturalist Observation
Species: Compost Fly (Bibio imitator)
This Photo:     Size, ventral, Male starting to twist
Other name: Garden Maggot

Thank you Reiner Richter & Even Dankowicz for confirming the id of this species for us

EXTRA - Photo Specific Information:
A very strange situation. We caught these two in the act (literally caught them and put them into an insect box while they were in the act). Normally they would have been fine. But she was panicking and got him so twisted he fell unconscious. Even then he didn't let go. In his "sleep" he must have had a dream and when he woke up he finished pretty quickly and they parted.
BUT HE WAS SOOOO TWISTED UP!
General Species Information:
Found in the Adelaide Hills and possibly elsewhere
A large number of flies can have their gender determined by the distance between the top of their eyes. Note here the male's eyes are touching, the females are well separated.
We asked Tony Daley if there were taxon groups of flies that had this trait. He replied "It seems there are examples of male holoptic eyes across the board, and can be defining for family, genus, or only at species level. Sometimes occurs in females too, eg Cecidomyiidae. I note that most Acalyptratae don't."
We've noticed some Tachinidae have "holoptic" eyes (ie continuous visual surface), but Rutilia don't.
The opposite to "Holoptic" is "Dichoptic", most female flies have dichoptic eyes. Small headed flies have females with Holoptic eyes & Robberfly eyes are dichoptic.

Copyright © 2015-2025 Brett & Marie Smith. All Rights Reserved. Photographed 04-Dec-2015
This species is an Australian Native Species, not listed in the SA Murray Mallee Survey of 2010.