Fake caterpillars: why do we use green and orange?

 

A) Brownish caterpillar from our lab colony (picture by Dr. D. Ingber). B) Picture from a plant-fed caterpillar (Picture from M. Rice, https://iapps2010.me/2017/12/18/fall-armyworm-in-malawi-state-of-disaster-declared/).

Caterpillar coloration is very variable and highly depends on their diet. In the lab, we rear them on artificial diet that is optimal for their nutritional needs but colors them in a dull brownish grey (the last day, we tryed to caged them in clip-cages made of small Petri-dishes and sealed with neon green foam sheet; these voracious beast fed on the foam and started to get an nice green tint...). In the field, as they feed on plant material (and also because it helps them to hid on plants), caterpillar tend to be greenish and this is the reason why we chose dark green Play-Doh to make our fake insects.

The orange pin is to mimic the head capsule of real lepidopteran larvae. The original idea was to have something a bit darker (hard to tell the real colors when you order online, right?) but this orange finally worked out well.

On aspect we would like to further explore, in addition to the diversity of bird attracted by plant volatiles, is the impact of visual cues on the bird behavior. This could be done by varying the colors used to make the caterpillars and comparing the bird preferences. To be continued...