Identifying a caterpillar can be a challenge. There are many insects that start life as larvae, and they do not all turn into butterflies or moths. Insects like craneflies, sawflies and beetles can have very caterpillar-like larvae. Here are a few examples:
A sawfly larva
, a syrphid fly larva 
,
a beetle larva
, and a cranefly larva 
.
If you do have a moth or butterfly larva, there are some good online keys you can try. The first three links below will take you to the interactive keys. The last two links take you to a couple of other sites I have found helpful.
Discover Life
What's This Caterpillar
Common Caterpillar Pests of Vegetables by Texas A&M University
Caterpillars of the Pacific Northwest
Caterpillars of Eastern Forests
You can also try using the terms shown below in the Bugguide.net search. For example, you can type in caterpillar tufts to find tufted caterpillars. Be aware that the search engine picks up on terms used in the image description, so there are times when the search may bring up irrelevant images and leave out relevant ones. Some of my best search results come from typing in things that are very obvious about the larva, such as, hairy caterpillar, green caterpillar, etc.
Bugguide.net has many images of caterpillars (221 pages of images as of Oct. 07). You can always try browsing through them starting here, but it may take some time to get through them all. You may also want to click the "caterpillars" tab next to "show images of" or you'll be adding a lot of extra time browsing the adult forms as well.
Of course, there are a few people on Bugguide.net who know many caterpillars by sight. So, take a picture of the caterpillar and the plant it's on and post it in ID Request. If you can't take a picture, you can try using the terms below to post a description in the General Discussion Forum. When possible it is helpful to post the length of the caterpillar, the plant it is feeding on, and the location where it was found. Even if no one knows the caterpillar immediately, people will often do research online or with Guides they may have access to.
Good Luck! I hope you find what you're looking for.
HAIR
Smooth (no hair)
Sparse Hair
Hair Tufts, Tussocks, or Pencils
Dense Hair
IDENTIFYING FEATURES
Knobs, Warts
Spines
Tubercles
Horns or Tails
Humps
BODY PATTERN
Camouflaged
Spotted
Middorsal Spots Subdorsal Spots
Speckled
Ringed (bands going around the body)
Lined
Middorsal Longitudinal Line Subdorsal Longitudinal Line
Oblique Lines
Banded (thick Line)
Middorsal Longitudinal Band Subdorsal Longitudinal Band
Streaks
Middorsal Dashes Subdorsal Dashes
Saddled
Contributed by Lynette Schimming
-------------------------------------
A sawfly larva
, a syrphid fly larva ,a beetle larva
, and a cranefly larva .If you do have a moth or butterfly larva, there are some good online keys you can try. The first three links below will take you to the interactive keys. The last two links take you to a couple of other sites I have found helpful.
Discover Life
What's This Caterpillar
Common Caterpillar Pests of Vegetables by Texas A&M University
Caterpillars of the Pacific Northwest
Caterpillars of Eastern Forests
You can also try using the terms shown below in the Bugguide.net search. For example, you can type in caterpillar tufts to find tufted caterpillars. Be aware that the search engine picks up on terms used in the image description, so there are times when the search may bring up irrelevant images and leave out relevant ones. Some of my best search results come from typing in things that are very obvious about the larva, such as, hairy caterpillar, green caterpillar, etc.
Bugguide.net has many images of caterpillars (221 pages of images as of Oct. 07). You can always try browsing through them starting here, but it may take some time to get through them all. You may also want to click the "caterpillars" tab next to "show images of" or you'll be adding a lot of extra time browsing the adult forms as well.
Of course, there are a few people on Bugguide.net who know many caterpillars by sight. So, take a picture of the caterpillar and the plant it's on and post it in ID Request. If you can't take a picture, you can try using the terms below to post a description in the General Discussion Forum. When possible it is helpful to post the length of the caterpillar, the plant it is feeding on, and the location where it was found. Even if no one knows the caterpillar immediately, people will often do research online or with Guides they may have access to.
Good Luck! I hope you find what you're looking for.
HAIR
Smooth (no hair)
Sparse Hair
Hair Tufts, Tussocks, or Pencils
Dense Hair
IDENTIFYING FEATURES
Knobs, Warts
Spines
Tubercles
Horns or Tails
Humps
BODY PATTERN
Camouflaged
Spotted
Middorsal Spots Subdorsal Spots
Speckled
Ringed (bands going around the body)
Lined
Middorsal Longitudinal Line Subdorsal Longitudinal Line
Oblique Lines
Banded (thick Line)
Middorsal Longitudinal Band Subdorsal Longitudinal Band
Streaks
Middorsal Dashes Subdorsal Dashes
Saddled
Contributed by Lynette Schimming
-------------------------------------