INVESTIGATION OF LIFE HISTORY. 55 



2,000 caterpillars per pair of beetles. This indicates that the number 

 of caterpillars consumed, and hence the amount of benefit derived, 

 depends to a considerable extent on the size of the prey, and, further, 

 that if gipsy moth caterpillars should be scarce in any locality a great 

 number of the smaller native species would be destroyed. 



Effect of Feeding Diseased Gipsy Moth Caterpillars to Calosoma Beetles. 



Among the feeding experiments begun in July, 1907, was one to test 

 the effect, on the health of the Calosoma beetles, of feeding them dis- 

 eased gipsy moth larvae. In the other feeding experiments where 

 gipsy moth larvae were used it was found that 15^ per cent of them 

 died from the disease known as the "wilt." A single pair of Calo- 

 soma beetles was fed, from July 23 to August 14, with caterpillars 

 which showed pronounced symptoms of the disease. Twenty-one 

 larvae were eaten, 3 were so badly injured that they died, and the 

 remaining larvae supplied to the beetles in the jar died from disease. 

 These beetles ate slightly less than in the case of other pairs that 

 were fed healthy food, but showed no bad effects and went into 

 hibernation at the same time as the other pairs. Unfortunately they 

 were placed in a galvanized-iron cage and died before spring, as was 

 also the case with other pairs that were wintered in the same kind 

 of cages. The death of these beetles may, therefore, be attributed 

 to the unsuitability of the cage rather than to action of the diseased 

 food consumed. 



July 8, 1910, an experiment was started with 2 pairs of old beetles. 

 One pair ate voraciously; the female oviposited freely, and died 

 August 16 following. The other pair ate very little, no eggs were 

 laid, and both beetles went into hibernation in August. 



All the experiments conducted would seem to indicate that the 

 beetles of Calosoma sycophanta are not susceptible to the "wilt" 

 disease. 



Each year large numbers of the gipsy moth caterpillars die in the 

 feeding jars from tins disease, and if it were seriously destructive to 

 the Calosoma beetles or their larvae it would long ago have been 

 necessary to give up the experimental and rearing work. 



Experiments in Feeding Calosoma Beetles with Gipsy Moth Caterpillars 

 from Sprayed or Poisoned Foliage. 



Several attempts have been made to determine whether adult 

 Calosoma beetles are injured or killed by feeding on gipsy moth 

 caterpillars taken from sprayed trees. In 1910 an attempt was made 

 to test this matter, and a small area of brush and scrub growth near 

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

 caterpillars collected later from time to time, in order to make a test. 

 The experiments were begun on June 17, 1910, and gipsy moth 

 caterpillars from tins poisoned area were used for food until July 13, 



