CO-Horts Blog

Thursday, July 11, 2019

Who's That Larva?

Posted by Sarah Schweig, Broomfield County Extension

Insects that undergo complete metamorphosis will go through a larval stage or stages in which they are unrecognizable from their future (adult) selves. It can be tough to identify larvae, but it’s important for a few reasons. While adults may be more familiar to us, larvae can make their mark on their environment, whether positive or negative, because they’re such voracious eaters. Larval and adult stages often have different roles in the environment as well. Some adult lacewings, for example, prey on garden pests as adults, but many subsist mainly on pollen and nectar. Green lacewing larvae, however, are sometimes called “aphid lions” for the quick work they make on the pests, and in fact they’re generalists and will prey on plenty of other unwanted garden guests as well. We've seen lots of interesting larvae lately - here are some highlights!

Carpet beetle larvae found in a camper van

Dermestid beetles are found throughout the state. While some like those of the genus Dermestes feed on meat-based materials, others like Anthrenus species can feed on wool-based furnishings, thus their common name, carpet beetles. They can be a pest in homes but are beneficial to natural ecosystems where they recycle nutrients by feeding on decaying matter.

Elm leafminer larvae in Siberian Elm

Elm leafminers (Kaliofenusa ulmicreate blotchy leafmines as the larvae eat and develop in elm leaves. Once the larvae are fully grown, they drop from the leaf to the ground where they pupate until they emerge as adults the following season. Some seasons are worse than others, but there is only one generation per season, and the damage is usually just an aesthetic concern.
Corn earworm pupa found under soil in vegetable garden

So no, this is not a larva, but this pupa steals the show for July. Corn earworms (Heliothis zea), are also called tomato fruitworms or cotton bollworms, depending on who they're bothering. The larvae are an important pest of all of these crops, and they pupate beneath the soil before emerging as adults. A closely related pest, which looks very similar at this stage, is the geranium budworm (Helicoverpa virescens). Both have multiple generations in a season, and the pupae can overwinter in mild climates or years.


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