February, '17] McCOLLOCH: UNDERGROUND INSECTS 187 



cave was placed eight feet below the surface of the ground and the roof 

 two feet below the surface. The floor space of this cave is five by seven 

 feet. The walls, roof and floor are six inches thick, and the roof is 

 reinforced. The entrance is through a manhole at one corner with an 

 iron ladder leading down to the floor. The advantage of the manhole 

 type of entrance is that it does not cause much change of temperature 

 when opened. The temperature was recorded in the same way as in 

 the case of the temporary cave. 



This cave was completed about the last of July and since then has 

 been used in the rearing of white grubs, wireworms, and false wire- 

 worms, as well as a number of other species. It has proved even more 

 satisfactory than the first cave and the temperature control has been 

 even better. From August 1 to November 1, the temperature was 

 held at from 75° to 65° and since then there has been a gradual decrease, 

 amounting to about one-eighth of a degree a day. The daily fluctua- 

 tion of temperature is also less in the cement cave. A number of 

 experiments were made during the summer to determine what influence 

 the cave had on the life-histories of various insects. Three generations 

 of the chinch bug egg parasite {Eumicrosoma benefica) were reared in 

 the cave and the life cycle coincided with that of the check reared in 

 the field insectary. Eggs of the false wireworms and corn ear-worm 

 hatched in the same length of time as those in the check. During the 

 time the.-e experiments were being run, the temperature of the field 

 insectary was varying from about 60° to 70° at night to about 100° 

 during the day, with a mean of about 80°. The temperature of the 

 cave was practically constant, being about 78°. 



The possibilities of this method of rearing insects, especially of 

 subterranean forms, seems to be very promising. The temperature 

 can be controlled to a much better extent than in many forms of elab- 

 orate apparatus. The fact that the daily range of temperature is so 

 small makes it possible to hold it at any desired degree for weeks at a 

 time. It is very probable that a carbon electric light connected with 

 a switch in the thermograph house would make it possible to quickly 

 rectify any drop in temperature. The conditions encountered in the 

 cave did not materially influence the insects under observation and the 

 length of the stages was the same as in the checks reared in the field 

 insectary. In fact, the conditions in the cave appeared to approxi- 

 mate those that would be encountered in the field bj^ the subterranean 

 forms studied. 



President C. Gordon Hewitt: This paper is now open for dis- 

 cussion. 



Mr. Franklin Sherman, Jr.: The paper just presented covers a 



