The Short Answer: Interesting that I received these two questions within a week of each other, both from the Buffalo, New York area. I’m pretty sure the same, or very similar, insects laid these egg masses on Tricia’s and Susan’s cars. I sent the photos to Dr. Gabor Horvath and Dr. Gyorgy Kriska, researchers at the Eötvös University in Budapest, Hungary who have studied why insects sometimes lay their eggs in the wrong place. Based on the photos, Dr. Horvath and Kriska suggested that these are egg masses laid by caddisflies in the family Limnephilidae. Most species in this large family lay their eggs on leaves overhanging water. When the eggs hatch, the caddisfly larvae drop into the water, where they develop in a fairly standard caddisfly way (see this caddisfly article). They glue together a house, which protects them as they feed on detritus. Eventually, they metamorphose into adults, mate, lay eggs on leaves and start the cycle again.
So why did they lay these eggs on cars, instead of on leaves? How does an insect, with a tiny brain, figure out where to lay its eggs in the first place?
It’s not that a caddisfly female thinks about where to lay. Her brain is coded with a recipe or algorithm for where to lay. For example, the instructions might say, fly till you find yourself over water. Then fly up until you come to a horizontal object. Lay your eggs there. I’m oversimplifying it, but the process is probably something like that. And for many insects, especially those whose eggs and larvae need to be associated with water, automobiles cause confusion. That’s what probably happened in both these cases.
Dr. Horvath and Dr. Kriska study insect “mistakes” in order to gain insights into how the vision of insects and other animals works. In the case of insects that lay eggs on cars, the answer seems to be related to polarized light. Light that enters our atmosphere is non-polarized, which means that the light waves are oriented in all directions equally. When light bounces off a horizontal surface, such as the surface of a pond or lake, however, the reflected light is mostly oriented in a single direction. We call that polarized light.
In the natural world, the most common sources of horizontally polarized light are the surface of a body of water, or the surface of leaves. Many insects have evolved to detect that polarized light as an indication of a good place to lay eggs. It’s how they know they are flying above water or leaves and not above dirt. It appears, for example, that Limnephilidae caddisflies use polarized light as one of the signals that suggest a good place to lay their eggs on leaves over water.
Unfortunately, for those caddisflies and other insects that rely on polarized light as an indicator of where to lay eggs, reflective man-made horizontal surfaces, like the dark-colored hood or roof of a car, or even asphalt road surfaces can also reflect light in a way that polarizes it. This can lead to insects laying their eggs on top of cars, which is what Dr. Horvath believes happened in this case.
Thanks: Thanks to Charley Eiseman, co-author of Tracks & Sign of Insects & Other Invertebrates for confirmation that these might be insect eggs, and to Dr. Horvath and Dr. Kriska for their help in suggesting what kind of insect might have laid them and why.
Polarized Light: If you are curious about how the polarization of light works, you might find this video helpful: https://www.youtube.com/watch?v=gP751qpm4n4
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I found some of this gel on my car yesterday after a rain. However, what I noticed is that wherever there was a blob of gel there was a spot where a bug had splattered on my car from the day before. I think that the bugs that I was hitting might have been caddisflies and their guts had the eggs in them along with some kind of desiccant which absorbs water and expands to create the gelatin overnight. So, in other words, I would hypothesize that the flies lay their eggs and there is no gel initially and the gel only shows up after it rains or the eggs get wet by some other means.
I seen these same things in Washington State. The only thing I noticed was we had recently traveled by car through a few large swarms of bugs. About a week later it rained and I noticed there were large clumps of clear jelly some with dots some without. After further inspection I could see that the dead bugs smashed into the car were swelling up into a clear jelly with the rain. I had many pictures of half transformed bugs which I may still have…I’ll have to check. Ive been a WA native my whole life and i didn’t recognized the bug or ever see anything like it although my dad says we would also see the jelly on his car every now and then and wonder what the heck caused it. Weirdest thing I ever seen, but I got to thinking there was an old unsolved mystery episode called the Oakville Rain where a mysterious clear jelly seemed to rain from the sky l. It apparently made people sick but they never figured out what it was. I think there may be a connection.
I’m so happy to find this!!! After swimming in my pool which I’m fact does have a tree overhanging, I have found tiny bugs in my hair (and extensions) that slime me! I thought it was a defense mechanism but now it makes total since, no matter what I put in there to kill them, I end up with slime that dries to feel like cement and probably pulled half of my hair out using a nit comb, I sometimes find a plastic looking black substance that’s small sometimes straight sometimes she’ll like appearance. I’m posting a picture of what it looks like when it’s dried, leaving a boil like place on my head. I also had what looked like a tail of an insect on my hand after swimming only when I tried to remove it, it took skin with it, almost like it melted into my skin. I e been to 3 drs and I’m pretty sure they think I’m insane, if anyone told me this was happening I would think the same. It’s destroying my life! Please help!
This is cool! I work for Amazon in Buffalo, NY and this morning after a long two days of rain every one of our vans was COVERED in these little blobs, thousands of them. Very neat to know what they are!