258 ILLINOIS ACADEMY OF SCIENCE 



II. EXAMPLES OF PHYSIOLOGICAL LIFE-HISTOKIES 



Some of tlie best known examples of physiological life- 

 histories are suggested by some of the insects. One of 

 the tiger beetles {Cicindela hirticollis Say) deposits eggs 

 in June ; these hatch in the sandy soil in which they are 

 laid, feed on ants and other insects, molting once or twice 

 during the summer. When the cold weather begins they 

 <?lose their burrows and remain below ground during the 

 winter. They begin feeding again early in the spring, 

 pass to the pupa stage, and emerge as adults in July. 

 After feeding for a few days the adults burrow into the 

 sand and remain until the following June when they come 

 out of hibernation, deposit their eggs and remain in their 

 habitats in some numbers so that in the ordinary sum- 

 mer, one is able to collect these old individuals mixed 

 with the new freshly emerged ones of the next genera- 

 tion. Thus in this species we have two years between 

 generations and some special conditions apparently 

 necessary both in the larva and in the adult, before they 

 will proceed with development at the time of the usual 

 hibernation period. 



The codlin moth of the apple passes the winter in the 

 larval stage, pupates after a few warm days in spring. 

 The pupae emerge as adult moths about the time that the 

 apple trees have begun to leaf out. They deposit eggs 

 which on hatching into small larvae provide the so-called 

 worms wliich are familiar in wormy apples. The small 

 larvae enter the young fruits and after feeding for a 

 time reach the fully grown condition, make their way 

 out, down to the tree trunk where they spin a cocoon, 

 pupate, and produce a moth which again lays eggs for 

 the second generation. Under certain weather conditions 

 a third generation is produced late in the summer, but 

 under certain other weather conditions no larvae of this 

 second generation of moths will proceed with develop- 

 ment until after some special conditions of temperature 

 and moisture have been imposed upon them. Thus we 

 see the physiological life-history of the codlin moth var- 

 ies with weather conditions and presents some special 



