Crablike Spiny Orbweaver Egg Sac

Subject: Looks like an egg sac
Location: South East NC
September 11, 2016 8:14 am
Hi, found this inside the rain deverter on my husbands truck this morning.
Do you know what it is?
Thank you!
Signature: Suzanne

Crablike Spiny Orbweaver Egg Sac
Crablike Spiny Orbweaver Egg Sac

Dear Suzanne,
The first thought that passed through our mind when we looked at your image is that this might be the egg sac of a spider, and we followed that supposition, which quickly led us to the Featured Creatures site and a nearly identical image of the Egg Sac of a Crablike Spiny Orbweaver or Spinybacked Orbweaver Spider,
Gasteracantha cancriformis.  The egg sacs are described on Featured Creatures as being:  “Ovate egg sacs, 20 to 25 mm long by 10 to 15 mm wide, are deposited on the undersides of leaves adjacent to the female’s web from October through January. The egg mass consists of 101 to 256 eggs, with a mean of 169 (based on 15 egg masses). After the eggs are laid on a white silken sheet, they are first covered with a loose, tangled mass of fine white or yellowish silk, then several strands of dark green silk are laid along the longitudinal axis of the egg mass, followed by a net-like canopy of coarse green and yellow threads. Eggs are frequently attacked by specialized predators, primarily Phalacrotophora epeirae (Brues) (Diptera: Phoridae), and occasionally Arachnophago ferruginea Gahan (Hymenoptera: Eupelmidae) (Muma and Stone 1971). Eggs take 11 to 13 days to hatch, then spend two to three days in a pink and white deutova stage before molting to the first instar.”  A similar image can be found on Nature Closeups and on BugGuide.

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