THE SORGHUM MIDGE. 53 



the approximate time required for the three stages was secured. At 

 Baton Rouge, La., the only successful attempt to secure the total 

 number of days in the life cycle gave 23J days from the time of 

 natural oviposition to the emergence of the adults. This develop- 

 ment took place during an average daily mean temperature of 79° F. 

 and an average daily mean humidity of 74.3. In San Antonio, Tex., 

 the development from egg to adult required 14 days during an aver- 

 age daily mean temperature of 84.7° F. and an average daily mean 

 humidity of 67.5. In the latitude of San Antonio, Tex., generally 

 speaking, the egg stage will cover from 2 to 4 days, the larval stage 

 from 9 to 11 days, and the pupal stage from 3 to 5 days, depending 

 upon the temperature and humidity. A very wide range in length 

 of time for the various stages has been recorded, but during the 

 normal temperature and humidity conditions in this latitude from 14 

 to 20 days are the average. 



LENGTH OF LIFE OF ADULT. 



In confinement, when no opportunity is afforded for oviposition, 

 the length of life of male and female is approximately 24 hours, while 

 females, when allowed to oviposit, live longer, generally about 48 

 hours. The length of the life of the female is largely dependent upon 

 the number of eggs she is capable of laying — death following shortly 

 after the egg supply has been exhausted. Females were found upon 

 dissection to contain from a dozen to upward of a hundred eggs. 



So far no feeding of adults has been observed. Close observation 

 has failed to reveal a single instance in which either male or female 

 partook of nourishment, their activity being confined solely to copu- 

 lation and oviposition. 



SEASONAL ACTIVITY. 



In the spring the midge appears with the first Johnson grass and 

 sorghum, and, as this grass heads considerably before the cultivated 

 sorghum, it may be said that by the time the latter has headed the 

 midge has become sufficiently abundant on the grass to make the first 

 sorghum infestation a heavy one. In the latitude of San Antonio, 

 Tex., the first midges to be found during the season of 1909 were found 

 actively ovipositing in Johnson grass on May 14. At this date the 

 neighboring sorghum had not headed, and it was not until June 19 that 

 the first brood emerged from the sorghum, which puts the date of this 

 first infestation at approximately June 5. 



Throughout the entire season the midge is found active upon its 

 hosts; in fact, as long as heading Johnson grass and members of the 

 sorghum family can be found in infested localities the midge is certain 

 to be present also. During the winter, when the activity of the midge 

 has apparently ceased, a few recurring warm days suffice to bring out 

 99370°— Bull. 85—11 5 



