240 PROCEEDINGS OF THE NATIONAL MUSEUM vol. lo* 



in this cage, along with cow dung, fungi, carrion, and dead leaves. 

 In this case the conditions approximated those in a moderately wooded 

 area, and the beetles could, because of the absence of a bottom to 

 the cage, burrow to any desired depth. 



All rearing cages were kept in partial shade, for seldom was any 

 species of Geotrupes collected in an open field. If there was a single 

 tree in a field the beetles always took advantage of its shade. 



After several months it was apparent that rearing was best under- 

 taken in the large enclosure. The smaller the container the more 

 difficult it was to induce the beetles to do anything. In addition, 

 moisture and mites both became problems. Several of the beetles in 

 the gallon cans laid eggs in wads of dung, but few of the eggs hatched. 

 Gamassid mites appeared to be the cause of this failure, for when the 

 mites clustered on an egg it never hatched. Fortunately, this problem 

 was relatively minor in the outdoor enclosure, where much of the 

 life history data was obtained. 



There was one question that often could not be answered. Was 

 the developmental rate of the immature stages either accelerated or 

 retarded when they were brought indoors, where temperatures were 

 usually higher and certainly fluctuated more rapidly than temper- 

 atures 6 or more inches underground? Early in the course of the 

 work it was proved satisfactorily that larval development could be 

 accelerated. One of the female blackburnii confined in a gallon can 

 indoors oviposited about March 18. On March 27 the egg hatched. 

 The larva became a second instar on April 16, a third in star on April 

 30, and a pupa on June 24. Subsequently it was found that in this 

 case the development of the early stages was not particularly rapid, 

 but that the time of development of the third instar to pupa was 

 greatly shortened. 



It was later found that acceleration of larval development was 

 possible only under certain circumstances. If the female beetle was 

 brought indoors and it oviposited, and development occurred from 

 the start at a warm temperature, then it was possible to produce 

 more rapid growth than was normal. However, if the egg was laid 

 in a natural habitat and remained there for even a few days, its 

 subsequent development could not be greatly affected even by much 

 higher temperatures. This conclusion was reached by doing a small 

 amount of digging in the cage of blackburnii at different times. On 

 each occasion 10 or 15 larvae were collected and kept alive in salve 

 boxes. These then could be compared with larvae subsequently 

 collected from the cage to see if there was any great difference in 

 growth between them. There was not. 



It can be argued that conditions in the cage were not natural, 

 the light being dimmed by the screen, the soil frequently dug up, 



