Flies don’t chew their food like we do. Instead they drink their food through a straw-like mouth part called a proboscis. We don’t have to drink our food, but sometimes it is fun, especially if you have fun straws.
Drinking liquids through a straw is easy, but if the food is very thick or solid it cannot move into the straw. If you keep sucking on the straw you remove the air inside and the straw collapses.
Flies have the same problem. They can only drink liquids through their long straw-like mouth part. Since most of the food available to flies is solid, they have to liquefy it. They do this by adding digestive juices to the food causing it to change so that it dissolves in the liquid juices. This liquid is soaked up by the spongy tip on the end of their “drinking straw” (proboscis). Then they suck up liquid food.For more information about how flies liquefy their food, see BARFING FLIES.
You often eat in a way that models how a fly eats.
Discover for Yourself
1. Dip the edge of very firm cookie into milk.
2. Place the wet end of the cookie in your mouth and suck the milk from it.
The milk makes the edge of the cookie very soft. When you suck the milk out of the cookie, you suck up some of the softened cookie.
This activity was adapted from Janice VanCleave’s Science Around the Year.