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.
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.
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”.
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.
An adult Wheelbug with its namesake armament and strong, piercing-sucking mouth part.
By the way, I counted 184 eggs in this group.
Roads End Naturalist 
How do you and Melissa find all these wondrous things? The rest of us must just walk right by them! Your posts are all great, and a good distraction in these strange times. Melissa’s tent caterpillars were fascinating. Thanks to you both!
Thanks, Kathy. Well, as that famous philosopher, Yogi Berra, once said, “You can see a lot by just looking”. We both tend to always be scoping out the area around us and noticing things either by their movement or that we had not noticed them there before. That’s where familiarity of place is helpful. Plus, we have been doing this a long time…
wow! Great find of that egg mass. Sharp eyes Melissa! I had heard that there was a significant uptick in the numbers of Wheelbugs hatching out , in response to the Marmorated Stink bug invasion. Good to know they are out there working!
Yes, she is a keen observer (as are you) and I benefit from that a lot. Interesting to think that wheelbugs may benefit from preying on the stink bug. I read that wheelbugs are one of the few predators that regularly preys on those guys.
Totally cool!!!
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Thanks, Betsy. Hope you and Walter are doing well.
I have to say that I always enjoy your blog posts! And I greatly enjoyed Melissa’s too! Anchoring oneself in the reality that “life goes on” in the natural world is just about the only way I can avoid getting really down about the situation we all find ourselves in! That said, I must say I’m a huge fan of the wheel bug, but the past two years, in our Bucks County, PA location, I haven’t seen nearly as many as I have in previous years. Fingers crossed they’ll plant some gorgeous egg masses around here again soon! Thanks so much again for all you do to bring us such beautiful and educational delights!
Thanks, AnnaLee. Stay safe.
Thanks, Mike. Again! I’ve seen a few assassin bugs and wondered what they were and if they sting. Hands off just on the looks!
They really aren’t aggressive biters, but I accidentally grabbed one once (so, naturally it was defending itself) when I plucked a tomato in the garden and it gave me a painful bite in the hand….not something I want to repeat.
Yeah, just don’t “attack” them. Once as a 5-6 yr old kid, I convinced myself that bees liked me. On a dare, I grabbed a honeybee. You know the rest…