THE GRASSHOPPER 



bodies to the object of contact. The young parasites thus 

 palmed off by their mother on the grasshopper, who has no 

 idea what has happened to him, make their way to the base 

 of the wing of their unwitting host, where they find a ten- 

 der membranous area which they penetrate and thereby 

 enter the body of the victim. Here they feed upon the 

 liquids or tissues of the now helpless insect and grow to 

 maturity in from ten to thirty days. Meanwhile, how- 

 ever, the grasshopper has died; and when the parasites are 

 full grown, they leave the dead body and bury themselves 

 in the earth to a depth of from two to six inches. Here 

 they undergo the transformation that will give them the 

 form of their parents, and when they attain this stage they 

 issue from the earth as adult winged flies. Thus, one 

 insect is destroyed that another may live. 



Is the Sarcophaga kelhi a creature of uncanny shrewd- 

 ness, an ingenious inventor of a novel way for avoiding the 

 work of caring for her offspring? Certainly her method 

 is an improvement on that of leaving one's newborn prog- 

 eny on a stranger's doorstep, for the victim of the fly must 

 accept the responsibility thrust upon him whether he will 

 or not. But Doctor Kelly tells us that the flies do not 

 know grasshoppers from other flying insects, such as 

 moths and butterflies, in which their maggots do not find 

 congenial hosts and never reach maturity. Furthermore, 

 he says, the ardent flv mothers will go after pieces of 

 crumpled paper thrown into the wind and will discharge 

 their maggots upon them, to which the helpless infants cling 

 without hope of survival. Such performances, and many 

 similar ones that could be recounted of other insects, show 

 that instinct is indeed blind and depends, not upon fore- 

 sight, but on some mechanical action of the nervous sys- 

 tem, which gives the desired result in the majority of cases 

 but which is not guarded against unusual conditions or 

 emergencies. 



When we consider the many perfected instincts among 

 insects, we are often shocked to find apparent cases of 



[21] 



