Organic Advice Column – May 25, 2022

Two Insects that Look Similar but are Very Different

There are two insects with stages that are easily confused with each other, but it’s important to keep them straight. One is a dangerous stinging pest, the other is beneficial and eats pest insects.

Asps, or puss caterpillars – Don’t touch!

Puss caterpillars, or asps, are the larvae of flannel moths. They have a pretty hairdo that resembles a pussycat’s fur. The adult moths are also pretty, but watch out! The fur that can be several colors conceals a serious and dangerous sting that comes from hollow spines along the back. The most common way people get stung is when the larvae fall out of trees or bushes and down the back of shirts. These insects are definitely pests and need to be controlled with Trichogramma wasps released in the spring or sprays of Bacillus thuringiensis or spinosad products. The Bt products will only kill moths and butterflies but the spinosad products kill most insects. Be careful with the use of both.

Unhatched native praying mantis egg casing

Hatched native praying mantis egg casing

With the same shape and color, egg casings of the praying mantis are often mistaken for puss caterpillars. They look like the other insect at a quick glance but are the temporary housing for many baby beneficial insects and of course should not be harmed.

There are basically two different kinds of praying mantids. The Carolina mantis (Stagmomantis carolina) is the native. These gray and brown camouflaged adult mantids are smaller and less showy than the larger and usually green Chinese mantids. The native egg casing is elongated and more slender. You can tell when they have hatched from the open slits that appear like tiny louvers.

Chinese praying mantis

Native praying mantis

The larger Chinese mantids (Tenodera sinensis) have been naturalized in the USA since at least 1895. Their colors range from brown (with a green wing stripe) to solid, bright green. Their egg casings (oothecas) are a little smaller than ping pong balls, light tan in color and fairly round. The front of these casings will also have the open slits that lets you know that approximately 200 eggs have already hatched and moved on. It doesn’t hurt to damage the egg casings at this point because they will not be used again. Before the slits are open the solid casings of both the Chinese and the native friends are viable so disturbing or destroying them will hurt or kill the eggs or young praying mantids.

Praying mantids can be purchased for release, but organically maintained gardens will attract them naturally.

For more information on the management information about these two important insects, visit the Praying Mantis topic at dirtdoctor.com.