14 BULLETIN 251, U. S. DEPARTMENT OF AGRICULTURE. 



for the first year — do not eat nearly as many caterpillars as beetles 

 that are older. On the other hand, the younger beetles seldom deposit 

 eggs, while the older ones are very prolific. 



Experiments conducted with small brown-tail moth caterpillars 

 indicate that a much larger number of this species was destroyed. 

 This is undoubtedly due to the small size of the caterpillars, and 

 similar results would probably be secured if small gipsy-moth cater- 

 pillars were used for food. 



In some of the laboratory experiments beef was offered to the 

 beetles for food. They fed upon it to some extent for a short time, 

 but after a week they refused to eat. Apparently they do not care 

 for this substance if caterpillars are available. 



EXPERIMENTS IN FEEDING BEETLES ON CATERPILLARS INFECTED BY WILT. 



Several experiments have been conducted in feeding sycophanta 

 beetles upon gipsy-moth caterpillars infected with the bacterial dis- 

 ease known as " wilt."- Experiments were started in July, 1907, 

 a single pair of beetles being fed from July 23 to August 14 with 

 caterpillars which showed pronounced symptoms of the disease. 

 Twenty-one larvae were eaten, three were so badly injured that they 

 died, and the remaining larva? supplied to the beetles in the jar died 

 from disease. These beetles ate slightly less than another pair that 

 were fed on healthy caterpillars. Both pairs entered hibernation and 

 those that were furnished diseased caterpillars showed no ill effects. 

 Several similar experiments have been conducted since that time, 

 and the results indicate that these beetles are not susceptible to the 

 '"wilt." Each year large numbers of gipsy-moth caterpillars die 

 from the disease in jars where Calosoma beetles are confined for 

 experiments, and if it was seriously destructive to the beetles or their 

 larva? the fact would have been determined by heavy mortality among 

 them. 



EFFECT OF SPRAYING ON BEETLES. 



Several attempts have been made to determine whether Calosoma 

 beetles are injured or killed by feeding on gipsy-moth caterpillars 

 taken from sprayed trees. In 1910 a small area of brush growth near 

 the laboratory was sprayed with arsenate of lead, and gipsy-moth 

 caterpillars collected from time to time were furnished the beetles 

 for food. Check experiments were also run in unsprayed areas. The 

 experiment failed to show that any of the beetles were injured by 

 feeding on caterpillars taken from sprayed foliage. Several col- 

 onies of beetles have been liberated in woodland that has been 

 heavily sprayed, and not infrequently beetles are found on street or 

 park trees which have been sprayed with arsenate of lead. Dead 

 beetles or their larva? are found very rarely, and thus it is evident 



