32 AMERICAN SPIDERS 



and quite thick. When the mass is disturbed by a gentle breeze, it 

 moves throughout its entire length with a graceful undulating mo- 

 tion." 2 The gossamer that falls during rainstorms in California 

 may well have its origin in some such concentrated area of silk. 



It is generally believed that ballooning and its resultant dispersal 

 is an instinctive impulse based on necessity, and that it constitutes 

 a protective device. The scattering of the many babies from the 

 site of the egg sac apparently works against overcrowding and 

 fratricide, and improves the chances of survival for each tiny aero- 

 naut. However, we must remember that flying is not the province 

 solely of the spiderling, and that spiders of all ages indulge in it, 

 limited only by size and weight. During their babyhood spiders 

 eat very little and probably represent no great menace to each other. 

 On the other hand, a high percentage of aeronauts may drown or 

 be dropped in situations where they have little chance of survival. 



THE EGGS 



The life of the spider begins at the time when a zygote is 

 formed by the uniting of the male spermatozoon with the ovum of 

 the female. It is believed that this occurs soon after the eggs are 

 laid by the female. The mother spider prepares a silken sheet on 

 which the eggs are placed. They issue one by one from the genital 

 opening beneath the base of the abdomen, and are bathed with a 

 syrupy fluid in which quantities of sperm from the stores in the 

 spermathecae have been discharged. At this time the eggs have a 

 very soft chorion, which is easily penetrated by the sperm at any 

 point. 



Spiders have long been listed among animals that are able to 

 reproduce parthenogenetically, that is, without having the eggs 

 fertilized by the male gamete. This belief has been perpetuated on 

 the basis of a few records, which are now completely discredited. 

 It has become well known that females can store the sperms of 

 males for weeks or months, and that they are thus able to fertilize 

 several masses of eggs in succession at distant time intervals from 

 the product of the initial fertilization. This curious fact has prob- 

 ably misled the few workers who have recorded parthenogenesis in 

 spiders, a phenomenon for which there is no unassailable evidence. 



2 L. O. Howard, "On Gossamer Spider's Web," Proc. Ent. Soc. Washington, 

 Vol. 3, pp. 191-2. 



