32 



BULLETIN 417. U.S. DEPARTMENT OF AGRICULTURE. 



LENGTH OF TIME REQUIRED TO COMPLETE LARVAL STAGES. 



The larvae that were reared in June and July, 1909, completed the 

 first stage in an average of 3 days ; the second in 3 days ; and the third 

 in about 15 to the date the larvae ceased feeding. The whole active 

 period of the larvae covers about 21 days for the series reared early in 

 the season. 



For the series that were reared in the fall of 1909, 4 days were re- 

 quired to pass the first stage, 10 days for the second, and 14 for the 

 third to the date the larvae ceased feeding, making a total of 28 days 

 for the active feeding period. 



The time elapsing between the date the larvae ceased feeding and 

 the date of pupation was secured from the series reared in the fall of 

 1909 and seven days were required at a temperature of from 68° to 75° 

 F. The prepupal stage, like the larval stages, is probably shorter in 

 the summer when the temperature is high and other conditions more 

 favorable to development. 



FOOD CONSUMED BY LARVAE. 



A large series of individual feeding records of larvae was conducted, 

 using jelly glasses about two-thirds full of earth. Very poor results 

 were secured with such small containers. All of the larvae in this 

 series died before pupation. The records of six specimens that 

 reached maturity before death are given in Table 5 to show the num- 

 ber of caterpillars destroyed by each. 



Table 5. — Food eaten by larvse of Calosoma scrutator. 



Hatched. 



Ceased 

 feeding. 



Malaco- 

 soma 



ameri- 

 cana, 



fourth 

 and fifth 



stages. 



Porthe- 



tria dis- 



par, fourth 



and sixth 



stages. 



Grand 

 total. 



1909. 

 June 22 

 22 

 22 

 22 

 22 

 22 

 22 



1909. 

 July 9 

 10 

 8 

 21 

 13 

 13 

 14 



Total. 

 6 

 4 

 7 

 6 

 5 

 5 

 7 



Total. 

 28 

 25 

 38 

 33 

 31 

 31 

 22 



34 

 29 

 45 

 39 

 36 

 36 

 29 









36 











The average number of mostly full-grown caterpillars consumed 

 by each of these larvae was 36. Using larger jars, giving each larva 

 more freedom, or under natural conditions, the writers believe that 

 larvae of this species will destroy as many large caterpillars as C. 

 sycophanta, which was reported in Bulletin 101 of the Bureau of En- 

 tomology to destroy an average of 41. The active feeding period of 

 O. scrutator in this series extended over 21 days, and this would have 

 been somewhat longer under more satisfactory conditions. 



It was proven in 1912 that these larvae consume with equal greed 

 pupae of Malacosoma americana and Porthetria dispar. One larva 

 that hatched June 24 of that year consumed 31 pupae of these lepidop- 

 terous species while other larvae consumed 15 to 18 pupae before be- 

 coming full-grown. 



