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



EFFECT OF " WILT " ON CALOSOMA LARWE. 



In the area infested by the gipsy moth a disease known as " wilt " 

 is quite prevalent among caterpillars. A number of experiments 

 have been conducted to determine whether sycophant a larvae, if they 

 were obliged to feed on caterpillars affected by this disease, would 

 contract it and die. The experiments were conducted in 1910 and 

 sycophant a larvae were fed on diseased caterpillars in breeding jars. 

 The results showed that the larvae of this beetle suffer little if any 

 from wilt. A few died, but no greater number than was the case in 

 check experiments where healthy food was supplied. Only a single 

 case has been noted in the field where Calosoma larvae had appar- 

 ently died from wilt, and as the specimens were not examined micro- 

 scopically, death may not have been due to this cause. Beetle larvae 

 are so commonly found in masses of gipsy-moth pupae and cater- 

 pillars which are dead or dying from wilt that if the beetle larvae 

 were susceptible to it, large numbers of dead specimens would be 

 found. 



EFFECT OF SPRAYING ON CALOSOMA LARV.E. 



The question has been repeatedly asked whether or not the spraying 

 of infested areas would result in destroying the beetles or their larvae 

 on account of the belief that many of them would feed on poisoned 

 caterpillars. Laboratory experiments, where caterpillars were taken 

 from sprayed trees and used as food for beetle larvae, show that the 

 death rate was no greater than normal, while observations in the field 

 have failed to reveal any case where the beetles or larvae fed upon 

 dead caterpillars or those in a dying condition from feeding on poi- 

 soned foliage. Apparently the beetles migrate in the field to locations 

 where food is abundant. If eggs have been deposited in sprayed areas 

 so that larvae are abundant, little doubt remains that some of them 

 may fail to secure food and die from starvation. No direct evidence is 

 available to indicate that either the beetle or the larva is killed as a 

 result of spraying, and we have always recommended that spraying 

 should not be discontinued in cases of gross infestation in order to 

 protect the beetles. The enormous increase of Calosoma seems to 

 indicate that a discontinuance of spraying is not necessary. 



STARVATION EXPERIMENTS WITH CALOSOMA LARV.E. 



Inasmuch as the ability of Calosoma larvae to develop depends upon 

 whether sufficient food can be found, a series of experiments was 

 carried on in 1908 to determine how long they would survive in the 

 different stages if no food was supplied. The larvae were placed in 

 jars containing a small amount of earth and no food was furnished. 



