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

Common Pool Bugs and How to Get Rid of Them

We are seeing small flies in our bathroom. Any idea what could be

How to Get Rid of Drain Flies

Top panels (a and b) are the insect specimens prior to pollen

Fly Fishing Bugs, Anglers

Cicadas Are Delightful Weirdos You Should Learn to Love

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

What is this large flying insect with seriously intimidating

Male flies are better at mating after fighting off a robotic rival