Fly larvae feed by forming a flowing fountain

Black solder fly larvae are maggots that are raised by startups all over the world as a source of sustainable protein. Raised in large bins, these larvae compete with thousands of their neighbors to eat twice their body weight in decomposing organic waste per day. In this experimental study, we show that the aggregation of larvae acts as an active fluid that “pumps” larvae towards a piece of food. We perform time-lapse photography and particle-image velocimetry analysis of top, bottom and side views of larvae in glass dishes. Around food items, larvae build a four-larvae-tall fountain with the bodies, where larvae crawl up through middle of the fountain and slide down the sides. For containers of 10,000 larvae, there is an outflow of tens of larvae from the food per minute. This pumping action ensures that the food is evenly dispersed between individuals.