Biston betularia cognataria (Pepper and Salt Moth)
Last September, I found this little caterpillar on a fruitless cherry tree outside our home. I may have spent a few hours watching it munch on leaves as I searched through literature and images in order to identify it. The twig-like larva is in the Geometridae moth family. Sometimes coming to a conclusion about a species takes a bit longer…and having an adult specimen can help, so I kept my caterpillar fed with an assortment of cherry, willow, maple, and alder leaves, watched it as it grew, then pupated…and waited over the winter months to see what would emerge.
Bilobed head of Biston betularia larva
I noticed last night when I went to brush my teeth that there was a little moth against the window of my insect habitat, watching me…and probably wanting out. It’s good to check the critter-keeper (that’s what I call my bug house) daily because otherwise you might leave the poor soul stuck inside and that never ends very well. In this moth’s case, I took a few pictures and then released him outside to fly away into the night.
Biston betularia (newly-emerged adult)
Newly-emerged adult (male) Biston betularia cognataria
This is a quick post, since I am always short on time, but please enjoy my photos. I do love the ones of the caterpillar most. The little cat ears are quite distinct!
Little “cat” ears
I’ve enlarged one to show you the spiracles, the little breathing holes that are along the sides of the caterpillar body.
Biston betularia cognataria
Showing spiracles near bi-lobed head
Many insecticides work by clogging up these holes with oils or soaps that are sprayed on the tree. Although the caterpillars do eat leaves, the aren’t really an economic pest at all. In fact, this species is quite remarkable in that it represents the fascinating study of natural selection and industrial melanism. Widely distributed across the world, Biston betularia or Pepper and Salt Moths became recognized for their adaptation of darkening pigment, allowing them to become more cryptic on trees in woodlands in Britain polluted by soot around the turn of the century. Check out my references for more information!
Newly-emerged adult with pupal case (on left)
Enlarged view of newly-emerged adult Biston betularia cognataria and pupal case
For further reading:
Bugging You From San Juan Island 