Whether you are a dedicated insect enthusiast or a gardener trying to control a plant pest, you may need to identify immature insects from time to time.
About 75% of insects undergo a complete metamorphosis beginning with a larval stage. In this stage, the insect feeds and grows, usually molting several times before reaching the pupal stage. The larva looks quite different from the adult it will eventually become which makes identifying insect larvae challenging.
Your first step should be determining the larval form. You might not know the proper scientific nomenclature for a particular form of larva, but you can probably describe them in laymen's terms. Does it look like a maggot? Does it remind you of a caterpillar? Did you find some kind of grub? Does the insect seem worm-like, but have tiny legs? Entomologists describe 5 types of larvae, based on their body shape.01of 05
EruciformGetty Images/Gallo Images/Danita Delimont
Does it look like a caterpillar?
Eruciform larvae look like caterpillars and in most cases, are caterpillars. The body is cylindrical in shape, with a well-developed head capsule and very short antennae. Eruciform larvae have both thoracic (true) legs and abdominal prolegs.
Eruciform larvae may be found in the following insect groups:
- Hymenoptera (Symphyta)
ScarabaeiformA beetle grub is a scarabaeiform larva. Getty Images/Stockbyte/James Gerholdt
Does it look like a grub?
Scarabaeiform larvae are commonly called grubs. These larvae will usually be curved or C-shaped, and sometimes hairy, with a well-developed head capsule. They bear thoracic legs but lack abdominal prolegs. Grubs tend to be slow or sluggish.
Scarabaeiform larvae are found in some families of Coleoptera, specifically, those classified in the superfamily Scarabaeoidea.03of 05
CampodeiformA brown lacewing larva is campodeiform. USDA ARS Photo Unit, USDA Agricultural Research Service, Bugwood.org (CC license)
Campodeiform larvae are usually predaceous and typically quite active. Their bodies are elongate but slightly flattened, with well-developed legs, antennae, and cerci. The mouthparts face forward, helpful when they are in pursuit of prey.
Campodeiform larvae may be found in the following insect groups:04of 05
ElateriformClick beetles have elateriform larvae. Getty Images/Oxford Scientific/Gavin Parsons
Does it look like a worm with legs?
Elateriform larvae are shaped like worms, but with heavily sclerotized - or hardened - bodies. They have short legs and very reduced body bristles.
Elateriform larvae are primarily found in Coleoptera, specifically the Elateridae for which the form is named.05of 05
VermiformGetty Images/Science Photo Library
Does it look like a maggot?
Vermiform larvae are maggot-like, with elongate bodies but no legs. They may or may not have well-developed head capsules.
Vermiform larvae may be found in the following insect groups:
Now that you have a basic understanding of the 5 different forms of insect larvae, you can practice identifying insect larvae using a dichotomous key provided by the University of Kentucky Cooperative Extension Service.
- "Borror and DeLong's Introduction to the Study of Insects", 7th edition, by Charles A. Triplehorn and Norman F. Johnson.
- "Encyclopedia of Entomology," 2nd edition, edited by John L. Capinera.
- Entomologists' glossary, Amateur Entomologists' Society (AES) website. Accessed March 22, 2013.
- Glossary, BugGuide.Net. Accessed March 22, 2013.
- "Recognizing Insect Larval Types," by Lee Townsend, University of Kentucky. Accessed November 8, 2016.