11 



has more direct influence than air temperature does in bringing about 

 variations in the life history of a subterranean insect like the changa. 



The cage used in procuring data on egg laying was a rectangular 

 wooden sash, 24 inches long, 8 inches wide, and 1 inch high. Lateral 

 grooves inside the sash, in which panes of glass could be run, per- 

 mitted the depth of soil placed between the panes to be regulated. 

 With a half inch of earth, the depth found to be most satisfactory, the 

 runways of the adults were always in sight and could be observed 

 without removing the glass. The cages were placed horizontally 

 and covered with a dark cloth to simulate natural conditions. Sliced 

 potato was at first used as food, but later sprouted corn was sub- 

 stituted. 



As eggs were laid they were protected from the parent changas by 

 a zinc ring the height of the space between the panes. It is possible 

 that the egg stage was affected by keeping the eggs in a location so 

 much more liable to temperature changes than the natural egg cham- 

 ber located some inches below the surface of the ground. However, 

 incubation of eggs in the cages seemed to be influenced as much by 

 the moisture content of the surrounding soil as by the air tempera- 

 ture. It was impossible to collect exact data on the relation of length 

 of incubation to soil-moisture content. 



The young changas upon hatching were isolated in shell vials 5 

 inches long and 1 inch in diameter, which contained sand and 

 sprouted corn. The changas were measured and transferred to vials 

 of fresh food once a week until arriving at the fourth instar. After 

 the fourth instar they were transferred to 250-cubic-centimeter Erlen- 

 meyer flasks containing earth and sprouted corn. All changas from 

 the fourth instar on were measured and transferred to fresh flasks 

 every second day. Moisture conditions in vials and flasks were kept 

 as near the optimum as possible. 



Individuals reared from the egg were noticeably smaller when the 

 final instar was reached than those taken in the field in the fourth 

 instar or later and brought to the adult stage. The former indi- 

 viduals averaged about 3 millimeters less in body length and about 

 1.5 millimeters shorter in medial length of the pronotum. 



It is not probable that the unnatural conditions under which the 

 rearing work was done affected the length of the developmental 

 stages very seriously, for nearly mature changas taken in the field and 

 brought through to the adult stage in the laboratory averaged about 

 the same length of time for the last two instars as did individuals 

 reared from the egg. Furthermore, the total length of the egg 

 stage and developmental and preoviposition periods, as determined 

 in the laboratory, equals about one year, which corresponds with 

 field observations. In nature the postembryonic developmental 

 stages are perhaps somewhat shorter than in the insectary. 



