MYSTERIES OF LIFE AND EXISTENCE — SNODGRASS 529 



species. Yet to all appearances she regulates her actions just as docs 

 the human workman. She is assumed to work automatically like a 

 machine, with no consciousness to direct her operations. Yet at the 

 end of one act something shifts her nerve impulses to the muscles 

 proper for the next act in the series that leads to the completed web. 



In some ways other than web-spinning Aranea seems to show some- 

 thing resembling intelligence. When an insect lands in the web, the 

 spider comes out of her retreat to inspect it and takes action according 

 to the nature of the captive or its display of activity. An ordinary fly 

 she carries off at once and makes quick work of it. In the case of a 

 grasshopper she is more cautious and deliberates before acting. Then, 

 according to Crompton (1950), she directs the end of her abdomen 

 toward the grasshopper and throws out a mass of silk, not in the form 

 of threads but as a sheet that completely enswathes the victim, which 

 now bound and helpless the spider drags to her retreat and leisurely 

 feeds on its blood. A wasp or a bee is first examined with suspicious 

 caution. The wasp, evidently recognized as dangerous, is either cut 

 out of the web or allowed to escape by its own efforts; a bee may be 

 successfully wrapped up and carried off. Such acts on the part of the 

 spider look like reasoned judgment, but since the spider is not sup- 

 posed to have reason, her behavior must be merely reactions according 

 to the nature of the visual stimulus. The spider presumably receives 

 a different ocular stimulus from the fly, the grasshopper, or the wasp, 

 each of which activates an appropriate set of muscles. If we accept 

 this explanation we are faced with the question as to how the nerve 

 connections are prearranged in advance to give the proper response. 

 Either the spider deceives us in appearing to act as if she has some 

 slight degree of intelligence, or we deceive ourselves in thinking that 

 she has none. 



The ground-living wolf spider, Lycosa, spins no web to entangle 

 her prey, but she encloses her eggs in a silken cocoon, which she at- 

 taches to her body and drags with her wherever she goes until the 

 young hatch. As observed by Crompton (1950) the mother Lycosa 

 now appears to have such a sentimental attachment to her ball of eggs 

 that she will fight to the death to retain it. Yet she does not know 

 her own cocoon from that of another spider, since she will readily 

 accept a substitute, or even an artificial cocoon made of cork. Clearly 

 the female Lycosa does not know that the cocoon she so sedulously 

 guards contains the eggs that will guarantee the perpetuation of her 

 species. Her apparent emotional attachment to the cocoon is merely 

 a temporary physiological condition necessary for the security of the 

 eggs during the incubation period, comparable to the development of 

 the milk glands and the physical modification of the uterus during 

 pregnancy in a mammal. In neither case is "maternal instinct" 

 involved. 



