Tipkiidae and Scoliidac 505 



While in nature normal hibernation is within the cocoon in the soil, 

 it has been found best in rearing to remove the cocoons from the soil 

 soon after their formation so as to avoid the high mortality caused by 

 the disease organisms so prevalent in soil. The cocoons are therefore re- 

 moved from the cross section trays by lifting out the cross partitions, 

 shaking out the soil, and sifting. 



The cocoons are then placed individually in 2 -dram homeopathic vials 

 and these are capped with fine copper wire screen. These individual 

 containers further prevent the spread of disease. A large number of 

 these vials may be stored in trays the bottoms of which are covered with 

 ordinary copper wire screen that allows ample air circulation when the 

 trays are stacked or held in racks. Racks so constructed as to hold the 

 trays and allow them to slide in and out are most satisfactory. 



The cocoons are held in the vials until emergence of the adults. As 

 the maintenance of large numbers of living cocoons — 40,000 to 50,000 — 

 in healthy condition through the long period of development and hiberna- 

 tion is not easy, for they should be kept at a fairly even temperature and 

 in a relative humidity of between 80 and 90 per cent. For this purpose 

 specially designed cellar rooms with controlled temperature and hu- 

 midity are best. These are refrigerated by means of special machines 

 such as are used in commercial cold storage plants. As the cocoons pass 

 from summer soil temperatures to hibernation the temperature is lowered 

 at 15-day intervals to correspond with the average mean soil tempera- 

 ture at a 3-inch depth for the particular period under consideration. It 

 has been found, however, that 3 8° F. is sufficiently low for hibernation 

 and that with insects of this group lower temperatures such as occur 

 during January and February need not be considered. As the hiberna- 

 tion period passes, temperatures are again increased at 15-day intervals 

 until the prevailing temperatures of summer are reached. Since a de- 

 tailed account of an ice-chilled cellar for hibernation has been published 

 by Allen and Burrell,* the reader is referred to those authors for further 

 details. 



As little has been published on soil temperatures with reference to soil- 

 inhabiting insects, a table has been prepared which may be of use to 

 workers in this and other fields. 



* Allen, H. W., and Burrell, R. W. Methods of obtaining emergence of Tiphia 

 adults from imported cocoons for use against the Japanese beetle. J. Agr. Res. 

 49:909-922, illus. 1934. 



