What is this on this fly's bottom? : r/insects

How to Properly Use Glue Traps for Insects (and Risks) · ExtermPRO

The Ins and Outs of Fly Light Traps

Insect Definition, Characteristics, Types, Beneficial, Pest

All about flies - Welcome Wildlife

What are these flies (?) and what are they doing? Seen in Toronto

Fly - Wikipedia

What are insects? - The Australian Museum

Bee fly, Parasitic, Pollinator, Hoverfly

Found a fly with a yellow butt! Never seen one like this before

What are these flies (?) and what are they doing? Seen in Toronto

Psychodidae - Wikipedia