Scarabaeidae 471 



tions being the capacity to hold moisture and supply food. For this 

 double purpose a vegetable mold is used. This consists of the thoroughly 

 rotted and disintegrated vegetable debris which accumulates beneath 

 tufts of various grasses, sedges, rushes, and similar vegetation growing 

 luxuriantly in meadows and other low-lying tracts of sluggishly draining 

 land. Forest leaf mold has not been found satisfactory. Vegetable 

 mold has a high water-holding capacity. This gives it a distinct ad- 

 vantage over mineral soils because it loses moisture more slowly and does 

 not become wet so readily when water is added to it. 



As a food, vegetable mold is readily consumed by larvae of Euetheola 

 and Cotinus,* often to the neglect of other food, while other forms, as the 

 larvae of the Japanese beetle, consume it more sparingly. It has been 

 possible to rear larvae of the Japanese beetle from egg to adult on 

 vegetable mold alone, although in such instances development is some- 

 what retarded as compared with that of larvae also supplied with other 

 food, such as grains of wheat. In the case of the Japanese beetle, best 

 results have been obtained when several grains of wheat were added to 

 the plant mold at intervals of about a week during the growing period. 

 These soon soften and germinate, and the larvae feed not only on the 

 grain itself but also on the growing rootlets. In the case of newly hatched 

 larvae, mortality may be considerably reduced by moistening the plant 

 mold with a mixture of equal parts, by volume, of water and milk previ- 

 ous to transferring it to the rearing boxes. This provides the larvae with 

 a highly nourishing food. Freshly hatched larvae treated in this man- 

 ner not only survive in greater numbers but, even when deprived of 

 wheat, have been found to pass through the earlier instars as rapidly 

 as other larvae, that were provided in addition with grains of wheat. 

 The use of a diluted milk is necessary to prevent the liberation of too 

 much ammonia due to the decomposition of the protein. Survival may 

 also be favored by burying the larvae in the vegetable mold instead of 

 merely placing them on the surface and allowing them to burrow down 

 into it on their own volition. 



The rearing boxes should be made about one-half full of plant mold 

 in the case of young larvae and two-thirds full for older larvae. In 

 either case a cushion of air is left between the surface of the plant mold 

 and the lid which is normally sufficient to meet the respiratory needs of 

 the larvae. 



In the case of sluggish larvae, like those of the Japanese beetle, the 



* Editor's Note: The late Anna Laura Hintze of Goucher College reported in Ann. 

 Ent. Soc. Amer. 18:31, 1925, the rearing of grubs of Co tints nitida on the following 

 foods, listed in the order of preference: sweet potatoes, Irish potatoes (if the skin was 

 broken), turnips, and carrots. The larvae showed a preference for a soil temperature 

 as high as 40° C. M. E. D. 



