White "Nest" in Window Frame: Likely a Moth Egg Mass

A white, foam-like 2-3 inch structure between a window screen and glass, with a black interior and black residue on wood frames, plus abundant spiders indoors. The homeowner in Green Bay wants identification before the exterminator arrives.

Probable ID: Moth Egg Mass

The description matches a moth egg mass (likely a gypsy moth or related species). Females lay eggs in sheltered spots—window frames, eaves, furniture. The "black interior" is developing caterpillars; the black residue is frass (caterpillar droppings) from hatched larvae.

Spiders Are Secondary

The spiders are attracted to the insects the moths and other prey draw. They're a symptom, not the cause.

What to Do

• Scrape off the egg mass into soapy water or alcohol.
• Vacuum frames and surrounding areas.
• Check other windows, eaves, and outdoor furniture for more masses.
• Reduce outdoor lighting to deter moths.

No pesticide needed for the egg mass itself. The exterminator can address any residual spiders or other pests.