226 JOURNAL OF ECONOMIC ENTOMOLOGY • [Vol. 2 



2 Recent Work in Insect Behavior 



As numerous as this group of animals is, comparatively little has 

 been done on them by workers classed as students of animal behavior, 

 and furthermore that which has been accomplished has been directed 

 largely toward species of relatively little economic importance. The 

 pomace fly (Drosophila ampelophila) has received much attention in 

 the Harvard zoological laboratories, chiefly because of its availability" 

 during the winter months, since it is easily reared in artificially heated 

 rooms. Carpenter^ has made a study of the reactions of this fly to 

 light, gravity and mechanical stimulation. The fly moves toward a 

 source of light, i. e., light has a directive effect, but this is not appar- 

 ent until a sufficiently powerful kinetic stimulus (light or mechanical) 

 has been exerted to induce locomotion. When very high intensities 

 are used, e. g., a 250 c. p. arc light, at 40 cm., the directive effect of 

 the light is apparently inhibited. Continued exposure to direct sun- 

 light caused many insects to come to rest in the least brightly illu- 

 minated regions and with the heads away from the source of light. 

 This last fact is explained because this is the position in which the 

 least light enters the eyes, and in which, as a consequence, the kinetic 

 stimulus is least. The great number of these flies around cider 

 presses, orchards and packing houses where fermenting fruit is often 

 found in quantities, leads one to wonder how these creatures find these 

 localities. It is, of course, a well known fact that these flies deposit 

 their eggs in fermenting fruit, and that the larv« or maggots feed 

 and develop in such matter. The most natural inference (because 

 these insects bear conspicuous compound ej^es) is that the food is 

 located by means of the sense of sight, but as a matter of fact ''they 

 find their food with great certainty even in the dark." This led 

 Barrows* to take up an investigation of their reactions to "odorous 

 substances." The flies were tested by accurate methods to various 

 intensities of substances commonly found in fermenting fruit, such 

 as ethyl alcohol, acetic and lactic acid, and acetic ether, each used 

 separately and also mixtures of them. The intensity of concentration 

 was known in each, an important consideration in such work. It was 

 found that the optimum strength of ethyl alcohol and acetic acid 

 is 20 and 5 per cent respectively. It was further ascertained that 

 cider vinegar, fermented cider and California sherry contain alcohol 

 and acetic acid in percents very close to the optimum strength. By 

 experiment it was next determined that the sense of smell by means 

 of which food is found, is located in the terminal segment of the 

 fly's antenna. 



