An unusual insect that few people get to see in iowa is the grass carrier wasp of the genus isodontia.
Brown eggs on window screen.
Well it s most likely that a moth has selected your window to lay her eggs.
For example if the color of the sac is pink or black then it is probably not a spider egg sac.
Moth and butterfly larvae are caterpillars.
Analyze the coloring of the larvae.
Come to think of it perhaps you ve seen these before.
In nature the nests are located in hollow stalks or stems of.
Observe the color to determine if what you are looking at might be a spider egg sac.
Some eggs sacs are brown yellow or even yellowish green.
Maggots are completely white.
The name refers to the nesting habits of the female wasp.
Insect larvae that would be on a window screen are either white or brown with black or white heads.
These look like moth eggs and if you look carefully in the lower left corner there is a tiny recently hatched caterpillar we will attempt to identify the eggs but we are guessing a member of the family saturniidae or the subfamily arctiinae.
A thread in the insect and spider identification forum titled strange eggs laid on window screen.
The wasps fill nest cavities with grass and occasionally other plant fibers till the nest resembles a loose pile of brown grass clippings stuffed into a protected opening.
Actually they look like patches of tiny little eggs hundreds of them.
Do you keep a light on at night near this screen.