380 The University Science Bulletin. 



behavior. . 



Naturally the larvae manifest a strong negative reaction to light, 

 and make effort immediately after hatching and when disturbed to 

 seek a shaded or other place of concealment. If placed near a light 

 or window they soon begin to crawl away from the light. It is 

 also quite noticable when the specimens are placed in a dark room 

 and a strong light is introduced at one end of the glass dish con- 

 tainer. This negative phototactic reaction persists throughout life. 

 It is at its highest sensibility to light just before pupation. Thus 

 pupse are most frequently found in shaded or dark places which 

 afford them a favorable means of protection. The adults, both male 

 and female, retain their negative reaction to light after emerging 

 from their pupal skins. During the period of sexual excitment which 

 follows a day or two later, the insects are still negative, and the 

 females remain decidedly so until their eggs are safely deposited. 

 Several hours or a day after egg-laying, they gradually become 

 indifferent to light, and finally a complete reversal of their former 

 reaction follows. The males also become positively phototactic 

 during the last days of their lives. The larvae of all stages feign 

 death upon being disturbed. However, when disturbance is con- 

 tinued from a few seconds to a minute at the most, they no longer 

 respond in the same manner. When disturbed the adult insects 

 make themselves very compact by drawing thorax up close to the 

 rest of body. The head is drawn upward and under the thorax, legs 

 and antennae are folded up, and death is feigned a considerably 

 longer time than in the larval state. The average feint lasts from 

 one to ten minutes 



VARIATION IN SIZE. 



The adult male insects are smaller, as a general rule, than the 

 female insects, but the small individuals are not always males. 

 There is much variation in the size of the adults. They are from 

 1.5 mm. to 4 mm. in length, the width also being proportionate. It 

 is difficult to determine the exact cause for this variation in size. 

 Poor nutrition evidently has effect upon the size. However, small 

 individuals appear among the large ones which have lived under 

 very favorable conditions. I noted marked variations in the size of 

 the different larvae of the same brood within a day or two after 

 hatching. I observed the fact, however, that the small, slowly de- 

 veloping larvae do not always produce small adults. 



