EPOW - Ecology Picture of the Week

Caterpillar Patterns

Caterpillar Devouring Leaf
Mindo, Ecuador

Explanation:  We've all seen this, but why are so many caterpillars bedecked with striking patterns and colors?

The classical explanation is aposematism, or use of obvious, bright colors as a signal to potential predators that consuming the individual will be harmful in some way, as in being poisonous or, as in the photo above, also having defensive spikes or hairs.  

However, a recent study (Mouy 2026) suggests that "repeated contrasted patterns" developed in at least some caterpillars to visually break up the body outline, particularly to confuse biting flies.  The study suggests that stripes can interfere with flies' visual navigation.  This apparently occurs when biting flies approach zebras, whose stripes serve to confuse the flies' visual senses and orientation.  

So the hypothesis is that the same occurs with multi-patterned caterpillars that would otherwise become the target and victim of biting flies.   

Along with an example of a woolly bear caterpillar we encountered in a previous EPOW episode, here are some other examples I encountered of the diversity of such patterns in various caterpillars and locations, although I did not observe them in the presence of biting flies (which, too often, seemed more focused on me!, ha).

Waccamaw River baldcypess wetland, South Carolina, USA: 

Lake Naivasha, Kenya, Eastern Africa:

Sahara Desert Camp,
Tunisia, North Africa 

But, of course, many caterpillars may lack such obvious markings and color diversity, such as this one found in Nokrek National Park in the Garo Hills of Meghalaya in northeast India.  For these individuals, it might suffice to have the sharp hairs as an adequate defense, or to blend into their environment as cryptic individuals.




  

Information:
    Mouy, H. 2026. The function of bands and dots in caterpillars: visual interference as an antiparasitoid defence? Evolutionary Ecology 40:25. https://doi.org/10.1007/s10682-026-10390-7.