I do love to be able to identify the critters I find and learn more about them. It often leaves me with more questions than answers, but it is good to keep those grey cells working!
I though this was a Zebra caterpillar, (the larva of an American noctuid moth), but it is actually a Pine Sawfly larvae Diprion similis.
This too could be a sawfly larva or it could be a Red-lined Panopoda Moth caterpillar. My photograph doesn’t give me enough to know for sure. Sawflies are unusual insects and I had never heard of a sawfly before. They seem to have a bit of an identity crisis going on. They don’t have a taxonomic group to which all sawflies belong and seem to be a bit of a cross between a wasp and a bee. The common name ‘sawfly’ comes from the female’s ovipositor. It functions like a saw blade and she cuts into stems or foliage to deposit her eggs.
You have to count the abdominal prolegs to tell the difference between a sawfly larva and a caterpillar. Caterpillars never have more than five pairs of abdominal prolegs, but sawfly larvae will have six or more. Another difference is that caterpillars have small fishhook like structures called crochets on the prolegs, but sawflies don’t have these. There is also a difference in the number of eyes. Caterpillars mostly have 12 stemmata (eyes) but sawfly larvae usually have just a singe pair.
Sawfly larvae are hairless and come in a variety of colours and patterns. They are plant feeders and most are specialist feeders that focus their feeding on only one type of host plant. There is a Birch Sawfly and the half eaten leaf could be a clue, but it seems the Birch Sawfly larvae have black dots down the back, so that doesn’t fit.
So is my friend a caterpillar or sawfly larva? It certainly seems hairless, but so are some caterpillars, despite the word ‘caterpillar’ that comes from the Latin words ‘cattus’ meaning cat and ‘pelose’, meaning hairy. Apparently the more hair a caterpillar has the more likely it is to be poisonous and shouldn’t be handled directly. Not a problem with my little friend.
As I am unable to count the prolegs or the stemmata and I can’t see if there are any crochets on the legs, I will have to abandon my attempt to identify it. Even if I had that macro lens I dream of, it wouldn’t have helped me here. Yet again I am aware of the minute detail that I need to observe and how complex the natural world is around me.