Volume 52, Number 2, September 2005:
Checklist of Kansas Orbweaving Spiders

Text-only version

ISSUE HOME PAGE

ABOUT THIS ISSUE
- about KSN
- about the author

IN THIS ISSUE
- introduction
- 1-6
- 7-16
- the orb web, prey, and economic importance
- 17-22
- 23-28
- predators, parasites and spider defenses
- Kansas orb weavers
- argiopidae
- tetragnathidae
- references
- acknowledgements

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Checklist of Kansas Orbweaving Spiders
by Hank Guarisco

PREDATORS, PARASITES AND SPIDER DEFENSES
The enemies of orb weaving spiders are legion. Mud dauber wasps (Sceliphron, Chalybion, and Trypoxylon) provision their mud nests with a wide variety of spiders, especially orb weavers. After locating a spider, the female wasp delivers a paralyzing sting, then transports her prey to an open mud cell that she has previously constructed. After capturing enough spiders to fill the cell, she lays a single egg, then closes the entrance with mud and begins constructing another mud nest. Once the egg has hatched, the paralyzed spiders become a ready food source for the developing wasp larva (13). I have routinely retrieved dozens of orb weavers (Neoscona, Argiope and Eustala) from four or five muddauber nests (Fig. 3). Incidentally, these mud nests often contain spiders that have not been collected by other means. For example, the Kansas record of Neoscona utahana in this checklist was based on a female taken from a mud nest.

The orb web is often the temporary home of a small, silver "dewdrop" spider (Argyrodes elevatus) which steals food from its host and may even kill and consume the much larger orbweaver! On several occasions, I observed this species feeding upon orbweaving spiders (16). Pirate spiders (Mimetus sp.) are specialized spider predators which invade a web, send signals to the host, mimicking prey or a potential mate by plucking the web, then attack its owner when it approaches to investigate (20).

The spherical egg sac of the black and yellow garden spider is often the target of many different predators and parasites (42). One winter, I examined several hundred egg sacs of this species in Douglas County and discovered the majority had been damaged or completely destroyed by birds (Fig. 4). The egg sacs appear in late summer and early autumn. By winter, the eggs have hatched but the spiderlings remain inside the egg sac until the following spring. Luckily, each egg sac containes approximately 1,000 eggs.

Spiders have a host of structural and behavioral defenses which enable them to survive their enemies' onslaughts (4). Some orbweavers (Neoscona crucifera, Larinioides cornutus) build webs at sunset and spend the day hidden in leaf retreats or under tree bark . Others (Eustala sp.) remain in exposed locations but have colors and patterns that match the background. A Eustala from western Kansas possessed a false-face pattern when viewed from the rear (15). The spiny-bellied orbweavers (Micrathena sp.) possess spines which disguise the outlines of their bodies. At the slightest disturbance, Gea heptagon drops from its web to the ground, legs folded, while the white areas on the abdomen instantly turn dark brown (47). However, dropping from the web was not an effective defense of garden spiders (Argiope sp.) against the mud dauber wasp, Sceliphron caementarium (Drury 1773) (2). The webs of garden spiders and Gea heptagon often have a parallel barrier web on one or both sides of the main web. In addition to adding structural support, these webs may quickly alert spiders of approaching predators.


Figure 3. The organ pipe mud dauber nest contains the bodies of many orbweaver spiders.