PPDL Picture of the Week

December 18, 2019

Most insects are smart enough to get out of the cold!

Tim Gibb, Extension Entomologist, Purdue University

An entomological rule of thumb is that insects are active in the spring, summer, and fall, but by the time winter hits, they are either smart enough to come in, out of the cold, or they have figured out a way to 'sleep' through it. This rule is followed by 99.9% of all insects, but there is one exception that is sometimes seen on sunny days in the middle of winter. People may sometimes notice thousands of tiny black specks jumping around on the snow. Because of the unusual timing and location of these insects, they become a curiosity and are often sent into our laboratory for identification and psychological evaluation. 

Our laboratory specializes in insect identification and these insects are usually found to be Snow fleas, however, we do not perform psychological evaluations on insects thus cannot vouch for their sanity. 

Snow fleas (Poduridae: Achorutes nivicolus), derive their common name because they actually live in and jump around in the snow. This jumping insect bears no other similarity with the common cat or dog flea, does not harm people or pets and seldom gets into homes. Rather, Snow fleas belong to a primitive group of insects called springtails (Collembola), so primitive that they do not even possess wings.  These feed on microscopic decaying bits of algae, fungi and bacteria that they find on the surface of the snow. They move about by using a unique, spring-like mechanism or tail at the back of the body (see accompanying photo). 

This appendage is bent forward, underneath the insect under tension and when released all at once, propels the insect into the air to give the appearance of a flea-like jump. 

What makes these insects so unique is that snow fleas are most active from November through March, precisely the time that most other insects are not. They may not be real smart, but they are certainly adaptable insects. 

Snow fleas are one more fascinating example of nature's exceptions to the rule.


Click image to enlarge


Moving black specks on snow surface identified as ‘snow fleas’.

Springtail (Collembolan) showing the rearward, spring-like, jumping mechanism.