10 DEPARTMENT BULLETIN 1267, U. S. DEPT. OF AGRICULTURE 



larvae are often infested with certain mites, which are decidedly in- 

 jurious to them and frequently cause their death. During the season 

 of 1915 these mites were so abundant and widely distributed that it 

 was found necessary to fumigate all samples of soil used in the breed- 

 ing boxes. 



The salve-box method of rearing larvae recommended by Davis 

 (5, p. 138) gave the best results and proved entirely satisfactory, 

 once the peculiar needs of the young larvae were ascertained. The 

 principal difficulties were to provide them with an adequate supply 

 of suitable food and to protect them from mites and disease fungi. 

 A few grains of wheat or corn were added to the boxes containing 

 the young larvae, but the larvae made no attempt to feed upon either 

 the grain itself or the plantlet issuing from it. Scarcely better 

 results attended the use of the different kinds of manure, either 

 fresh or old and thoroughly weathered. The fine, fibrous rootlets 

 of the corn plant were also tried, but without success. Finally, a 

 satisfactory food was found in a well disintegrated, brownish plant 

 residuum, or vegetable mold, a thin layer of which occurred fre- 

 quently in an old pasture at Tappahannoek, where the species bred 

 abundantly. At first this material was gathered beneath tussocks of 

 the common rush (Juncus ejfusus) where it consisted of the broken 

 and decayed culms of this plant, but subsequently was obtained 

 with much less difficulty in connection with certain grasses belonging 

 to the genus Paspalum and with Japan clover. It was the original 

 intention to utilize this material, owing to its softness, merely as a 

 medium in which the young and tender larvae might be kept with 

 the least chance of suffering injury. At first a grain or two of wheat 

 was added to each of the boxes containing this material, but it was 

 soon noticed that the wheat was le-ft untouched, whereas the vegetable 

 mold decreased rapidly in amount as the larvae grew and was re- 

 placed by excrement. The wheat kernels were thereafter omitted 

 and finely sifted vegetable mold alone used with entire success. 



A larva, after emerging from the egg, was carefully removed to a 

 small tin salve box previously half filled with a quantity of the vege- 

 table mold, finely sifted and slightly moistened. The young larva 

 would invariably burrow into the mold and excavate for itself an 

 irregular cavity, or cell, and there feed upon the surrounding ma- 

 terial. When this had been consumed, the larva was temporarily 

 removed from the box, the feces and other wastes cleaned out, and a 

 fresh supply of mold added. 



As the larvae grew, the amount of mold consumed by them in- 

 creased rapidly, necessitating frequent replenishing. The plan was 

 adopted of substituting for the vegetable mold a kernel or two of 

 corn, previously softened by soaking in water overnight. With larvae 

 from half -grown to full-grown this proved to be a satisfactory substi- 

 tute for the mold, and greatly lessened the work of caring for them. 

 Fresh kernels were added only when the old ones had been almost 

 consumed. 



Considerable difficulty was experienced in protecting the larvae 

 from the minute mites previously referred to, specimens of which 

 were identified by Nathan Banks as the hypopus stage of Rhizo*- 

 glyphus phylloxerae Riley. During the season of 1915 this pest was 



