Well it s most likely that a moth has selected your window to lay her eggs.
Brown eggs on window screen.
Insect larvae that would be on a window screen are either white or brown with black or white heads.
A thread in the insect and spider identification forum titled strange eggs laid on window screen.
The name refers to the nesting habits of the female wasp.
You ve opened the curtains to take a look outside and you notice small light colored dots appearing on an area of a window or window screen.
Do you keep a light on at night near this screen.
Maggots are completely white.
However this is not true of all egg sacs.
For example if the color of the sac is pink or black then it is probably not a spider egg sac.
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.
Caterpillars vary in color in accordance to their surroundings and as they grow larger.
Moth and butterfly larvae are caterpillars.
Come to think of it perhaps you ve seen these before.
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.
In nature the nests are located in hollow stalks or stems of.
Some eggs sacs are brown yellow or even yellowish green.
An unusual insect that few people get to see in iowa is the grass carrier wasp of the genus isodontia.