THE SPIKE-HORNED LEAF-MINER. 13 



this species are active throughout the entire year, appearing in 

 abundant numbers over the grain fields during the months of Feb- 

 ruary, March, and April. The males do not live quite as long in the 

 rearing cages as do the females. They may live from eight days to 

 four weeks, but generally not over two weeks. The females may live 

 from three to five weeks and oviposit during most of this time. This 

 long period of oviposition accounts for the complete overlapping of 

 the broods. The first progeny may have progressed to the pupal 

 stage some clays before the last eggs of its mother have been de- 

 posited. The females live only from three to five days after they 

 cease to oviposit. 



The flies appear the most active when the temperature ranges be- 

 tween 85 and 95 degrees F., and when below TO degrees they become 

 sluggish in their movements, especially so in flight. 



Adults are fond of sweets and lived for a longer period in cages 

 supplied with a quantity of sugar solution than in cages not so pro- 

 vided. 



MATING. 



Adults generally begin to mate the second or third day after 

 emergence; sometimes mating occurs on the day of issuance. They 

 apparently mate several times during life. They remain in copula 

 from a few seconds to thirty minutes or more. The female is able 

 to fly about while in coitu with the male, the added weight being 

 apparently no great hindrance in flight. 



NUMBER OF GENERATIONS. 



According to the rearing experiments conducted by the senior 

 author at La Fayette, Ind., there are at least three generations from 

 about the middle of May to the first of October, after which the 

 species goes into hibernation. He found apparently six generations 

 in the latitude of Columbia, S. C. Many of the larvae of the last 

 generation at both places did not reach maturhVy. Some died upon 

 maturity of the plants and others were killed by frost. 



Rearing experiments in the vicinity of Pasadena, Cal., show that 

 there are at least eight generations of this insect throughout the year. 



The first and second generations are generally well defined, but the 

 others overlap completely, so that all stages of the insect may be 

 present at one time. In southern California it may be found in all 

 stages throughout the entire winter. 



LIFE CYCLE. 



The average life cycle in the vicinit}^ of Pasadena, Cal., is con- 

 siderably longer than in the vicinity of Columbia, S. C, because in 

 the former locality the insect reproduces throughout the winter 

 months, when the stages are very slow in development. The average 



