How to Tell If Flies Are Pregnant

One way to tell if flies are pregnant is their behaviour. Normally, female flies will seek a nest made of acetic acid – a chemical found in fermenting fruit – and lay their eggs there. But when a female fly becomes pregnant, her behavior changes and she starts to focus on laying eggs instead of sex. A female fly will lay five to six batches of 75 to 120 eggs at a time. These eggs hatch within a day. This means a single pregnant female will wipe out hundreds of fly larvae.

However, there are exceptions to the general rule. For instance, in one family of flies known as tsetse flies, a female will produce offspring 100 percent larger than she is. This is because a female tsetse fly cannot have more than one baby at a time. This means that she must have a long life in order to continue to produce offspring, which could sustain the species.

Female house flies may be pregnant if they are laying eggs in your home. During their gestation period, they can lay hundreds of eggs. They will also spend most of their time in decaying organic matter. This means they are more likely to have parasites or pathogens in their diet. So, if you see a dopey, fat fly at your kitchen window, it may be an egg-laden female flies.