June, '09] journal of economic entomology 227 



The eyes of insects have long been studied for their structure and 

 physiology and one of the most important studies recently made on 

 the image-forming powers of eyes was carried on by Cole." This 

 investigator experimented on Variessa antiopa (the mourning cloak 

 butterfly), Ranatra (the water scorpion), Tenehrio (the meal worm), 

 and again the pomace fly, also several other animals. This work, 

 though not conclusive for some of the species studied, provides con- 

 clusive evidence that at least the mourning cloak butterfly and the 

 water scorpion of the animals possessing compound eyes have image- 

 forming powers. This evidence is further augmented by recent 

 experiments by the writer** on two common species of flesh-flies, Lu- 

 cilia ccesar, and Calliphora vomitoria, with the further evidence that 

 the eyes of these flies have this power not so well developed as the 

 butterfly, which is probably correlated with differences in habit, the 

 flesh-flies being more dependent on their sense of smell. Parker^ in 

 his investigation of the light reactions of the mourning cloak butter- 

 fly, discovered that it reacts to bright patches of sunlight. The 

 larvfp of Corethra plumiconiis, a short-beaked mosquito, have received 

 the attention of various investigators, among them Harper,'' who has 

 investigated experimentally their daily depth migration. Ants have 

 formed the basis of a number of classical works represented by Lub- 

 bock, Forel and Wasmann, and still these interesting creatures re- 

 ceive the attention of many recent investigators with results fully as 

 significant, due to the application of new and more accurate experi- 

 mental methods. IMuch of this work has however taken the form of 

 comparative psychology, as has the splendid work of Turner.^ The 

 investigations of Fielde.^^ and Fielde and Parker.^^ have afforded us 

 much information on the sensory reactions of these organisms. 



The above references have been made to afford some idea of the 

 nature of the work carried on by students of animal behavior, and it 

 will be seen that that which concerns the economic worker most is 

 the experimental method applied, since the species studied have little 

 or no significance from the economic standpoint. But it is this experi- 

 mental method, carrying with it utmost accuracy, that may well con- 

 cern us who are interested in the control of insect pests. What is 

 most needed at this time in the study of economic species. — granting 

 the importance of a knowledge of life histories, — is a knowledge of 

 its reaction to a given stimulus (the optimum stimulus) not only at 

 one period of its life history but throughout every active period, 

 because the reaction of an animal at one stage may not be its reac- 

 tion at another, e. g., the flesh-fly, Lucilia ccesar. Though others sup- 

 posed its reactions to light to be of a rather simple nature, which is 



