Egg Patterns

There is no better designer than nature.

~Alexander McQueen

While out in the yard looking at the tent caterpillars the other day, Melissa turned around and saw an interesting pattern on the trunk of a small tree. The pattern and details of the egg tops told us it was the egg mass of a Wheelbug, Arilus cristatus. Wheelbugs (and many other members of this family of insects known as assassin bugs) typically lay a patch of eggs covered with a resinous substance that hardens as it dries. This is a fairly large egg mass, measuring about 2 inches from top to bottom. If you are bored inside today, perhaps you can guess how many eggs are here, and then count them…you may be surprised.

184 wheebug eggs

Egg mass of a Wheelbug attached to a small tree (click photos to enlarge)

A closer view shows the typical fringe-like border around each egg top. I’m not sure what the function is, but I am guessing it could be to increase surface area for oxygen absorption.

184 wheebug eggs closeup

Close-up of the egg mass shows the fringe along the top of each egg.

A side view shows the eggs are somewhat bottle-shaped and tightly stacked together. One reference described the eggs as looking like “brown bottles with fancy stoppers”.

wheell bug eggs from side

Side view of eggs…the tiny dots are pollen grains.

These should hatch sometime later this spring and a horde of tiny reddish-orange and black (at first) robotic insects will be unleashed. I am guessing they may prey on one another as well, so their numbers will be greatly reduced before they reach adulthood in late summer (there is one generation per year). Once they are at that stage (over an inch long), they are formidable predators of many types of insects from caterpillars to bees. They are important predators of some pest species like the introduced and invasive Brown Marmorated Stink Bug, and some hairy caterpillars (like tent caterpillars) that are avoided by many birds. With their distinctive gear-like crest and large size, they are fascinating to observe, but handle them cautiously (or better yet, not at all), as they can inflict a painful bite with that long, needle-like beak.

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An adult Wheelbug with its namesake armament and strong, piercing-sucking mouth part.

By the way, I counted 184 eggs in this group.