ii2 AMERICAN SPIDERS 



of the young spiderlings, often for many weeks after their emer- 

 gence from the egg sac. 



The opening to the surface is the spider's only contact with the 

 outside. It is the vulnerable element in the circumscribed abode, 

 but at the same time it allows the creature to be menaced from only 

 one direction. On the surface, an inferior sensory equipment places 

 the trap-door spider at great disadvantage in combat with its 

 specialized enemies. Within the burrow, it faces the enemy pro- 

 tected by a silk door, and should that be torn away, it still has a 

 favorable situation for the use of its strong jaws. 



While demands for privacy have probably inspired the perfec- 

 tion of the underground castle of the trap-door spider, it is more 

 intriguing to think of the domicile in terms of response to the rav- 

 ages of some arch enemy. By far the most fearsome assailant is the 

 spider wasp, a common name for various species of Pompilidae, 

 which are exclusively spider predators. Other enemies may wreak 

 their toll in an insidious way and possibly destroy more individuals 

 than does the wasp, but this gleaming tyrant is a predator of the 

 first magnitude whose prey is the large, adult spider and whose 

 victory is won in hand-to-hand struggle. 



Actively foraging over the soil, unerringly directed by a sense 

 not conditioned by previous experience, the wasp arrives at the 

 trap door, beneath which sits the prospective victim possibly 

 aware, through its delicate tactile sense, of the presence of an in- 

 truder. If unprepared, or if its resistance is finally broken down, 

 the spider quickly finds itself confronted by an enemy that has lifted 

 the trap door or gnawed through it and entered the spacious bur- 

 row. The struggle that ensues is not a battle of giants. It is a very 

 unequal one from which the wasp almost always emerges the victor. 

 Swift and sure in movement, liberally endowed with fine sensory 

 equipment, and armed with a deadly sting, the wasp confidently 

 assails a larger creature fighting on a prepared battleground in the 

 deep recesses of its burrow. After a brief struggle the wasp para- 

 lyzes the spider with venom from its fiery sting, whereupon it 

 proceeds to deposit on the spider's abdomen an egg, from which 

 will hatch a voracious larva. Doomed to lie helpless while furnishing 

 fresh food for the larva, virtually dead if not actually so, the once 

 mighty spider finds its castle converted into a crypt. Industrial 

 skill has failed to make the burrow impregnable to its most formid- 

 able enemy. 



During the growing period, when the spider is remodeling and 



