4 BULLETIN 1201, TJ. S. DEPARTMENT OF AGRICULTURE. 



Potato -beetle larvae,. — Larvae of the potato beetle were collected 

 on potato plants and when brought to the laboratory were placed 

 in cheesecloth cages, 9 inches square by 12 inches tall. The larvae 

 were so well mixed before they were placed in the cages that each 

 cage contained about the same number in the various instars. 

 Sprayed or dusted potato-plant foliage was given to them daily. 

 Parasitism was common only among those in the last instar. 



House flies. — Flies were reared in specially constructed screen- 

 wire cages, 12 inches square by 18 inches tall, each of which con- 

 tained one-half gallon of moist bran mash. The females readily 

 oviposited in this mash, which later served as food for the larvae 

 and which proved a good substitute for manure. Large numbers 

 of flies were thus reared, some of which were fed poisoned food 

 in these cages, while others were transferred to small observation 

 screen-wire cages in which they were dusted with powders. 



Aphids. — Some of the aphids tested were sprayed or dusted out- 

 side the laboratory, but most of them were treated inside the 

 laboratory in a manner similar to that described in another paper 

 (60, p. 508). 2 



Honeybees. — Twenty young worker bees of practically the same 

 age were placed in each of many screen-wire experimental cages 

 and were fed in a manner similar to that described in another pub- 

 lication (61, p. 181). The sawfly larvae were treated as described 

 for aphids. 



Silkworms. — Silkworm larvae were reared in the laboratory and 

 were fed leaves as follows: Mulberry-tree leaves were dusted or 

 sprayed with the various preparations and with tap water (used as 

 a control), an atomizer being used in all the spraying experiments. 

 The leaves after having been dried in the air were cut into small 

 strips which were then placed in small screen-wire cages. An effort 

 was made to put approximately the same amount of food in each 

 cage, so that a rough comparative estimate of the food consumed 

 could be made; this procedure was also followed while feeding 

 the other species of chewing insects. Ten normal silkworms, all 

 of practically the same size and not ready to molt, were put in each 

 cage. Counts were made daily (except on Sundays), the cages 

 being cleaned and treated food being renewed at the same time. 

 No disease was noticed among these larvae. 



Fall webworms. — Webs of the fall webworm were collected in the 

 fields on Monday from a variety of plants; after being brought to 

 the laboratory, these webs containing the webworms were kept in 

 large cages with a small amount of food till Tuesday noon, by 

 w r hich time the larvae were well mixed according to size (all instars 

 but the first one), and by this time they were very hungry. Tuesday 

 morning approximately the same amount of mulberry-tree foliage 

 was placed in each of several wide-mouthed bottles containing 

 water; it was then sprayed or dusted, and when the foliage was dry 

 each bottle with contents was placed in a large battery jar, 8 inches 

 in diameter by 12 inches tall. Tuesday afternoon an effort was made 

 to place approximately the same number of webworms in each jar, 



2 The figures (italic) in parentheses refer to " Literature cited," p. 54. 



