What’s That Bug (Egg): Mantids and Katydids

Posted by Jessica Wong, Master Gardener Coordinator, Broomfield County Extension 

Winter can be a dull time for an entomologist. Like many plants, some insects go dormant for the winter. But now it is spring and the insects have resumed activity and so have the entomologists. 

Something that looked and felt a bit like a packing peanut glued to the branch of magnolia was brought in to the office a few weeks ago. This “packing peanut” is actually an egg case of a European mantid, Mantis religiosa. European mantids are non-native to Colorado, but they are well established here. In fall they lay multiple eggs (sometimes hundreds!) covered with a dried insulating foam on pretty much any solid surface. The eggs survive through the winter and start hatching in late spring. With this heat wave, some baby mantids might already be out. They look like the adults, but smaller. 

European mantid egg case on magnola. Photo by Jessica Wong

Gardeners like mantids because they are predators that feed on various insects, including some pests. However, mantids can be picky eaters and may not provide effective pest control. They mostly feed on gnats, flies and bees. A young mantid may cannibalize others as they emerge from the same egg case, and an adult female typically only eats the male during mating if she is starved.

Female European mantid laying eggs. Photo from bugguide.net by Lynette Elliot

More recently, a butterfly bush twig with two meticulous rows of eggs came in to the office. These are the eggs of a broad-winged katydid, Microcentrum rhombifolium. Their eggs can be found in double rows on twigs or in single rows on leaf margins. Similar to mantids, these katydids lay eggs in the fall that hatch in the spring. Katydids are herbivorous and will feed on the leaves of shade trees and other ornamental plants. However, they do not occur in high concentrations and typically do not cause harm to plants.

Double row of broad-winged katydid eggs on butterfly bush. Photo by Jessica Wong

Broad-winged katydids are seldom seen, but are often heard at night in the summers in Colorado. The males make loud “lisp” and “tick” sounds, and females respond with less audible clicking. Katydids produce sounds by rubbing the bases of their wings together - a process known as stridulation. On the base of one forewing is a set of tiny pegs called a file, and on the other forewing is a ridge called a scraper. The wings also have a smooth membrane that amplifies the sounds made from rubbing the file and scraper together.

Spring has just begun, but these insects have me dreaming of summer already.

Broad-winged katydid male. Photo from Colorado State University "Colorado Insect of Interest"