CHRYSANTHEMUM MIDGE. 9 



Longevity of adults. — In the life-history studies it was found that 

 males usually live less than 12 hours, while the females live from 2 to 

 3 days, in captivity and when not mated. Mated females probably 

 do not live over 24 hours. In the case of three males which were seen 

 to emerge after 1 a. m., all were found dead at 5.45 a. m. These re- 

 sults are given in detail in Table I. 



Activity. — The males are not often seen on the wing, as they die 

 shortly after mating, which takes place during the early morning 

 hours, almost directly after emergence. When on the wing, how- 

 ever, they are very active. The females, while generally rather 

 sluggish, may show great activity at times, especially in the early 

 morning and just prior to egg deposition. Dietz observed that on 

 cool days when the temperature was 50° F. in the daytime, and cooler 

 at night, the adult females were exceedingly active. Emergence rec- 

 ords taken on many cages show that there are a somewhat larger 

 number of females than males, the actual count being 464 females 

 to 365 males. 



Egg deposition. — The female when laying eggs keeps her legs at 

 equal distances apart and the ovipositor held at right angles to the 

 rest of the body, beginning probably at the third or fourth abdominal 

 segment. If not disturbed she acts with great precision. On one 

 occasion a female was carefully observed during two operations, la}dng 

 34 and 19 eggs respectively. The first oviposition period lasted exactly 

 3 minutes and 30 seconds, the second only 1 minute and 20 

 seconds. An interval of only 10 seconds elapsed between the oper- 

 ations. The tip of the long flexible ovipositor is thrust between the 

 pubescent hairs of the young terminal growth and pressed down firmly 

 on the surface. During deposition the eggs may be seen moving 

 down the tube with great rapidity, accompanied by slight contractions 

 of the ovipositor. Because of its darker color, the egg is plainly visi- 

 ble through the walls of the ovipositor. The number laid at one time, 

 according to Table II on page 10, varies from 5 to 135, with an aver- 

 age of 32. Guyton (31) found that "the number deposited by each 

 female is from 80 to 150." The eggs are usually placed in irregular 

 masses, although they may be placed in strings or chains. During 

 the whole operation the ovipositor is thrust around in a very nervous 

 manner. At times when the female moves slightly about, the body 

 is not straightened out but dragged along to the new place of deposi- 

 tion, in the original bent position. Although egg-laying may take 

 place up to and later than 4.30 p. m., the maximum egg-laying occurs 

 from the early morning hours up to midday. The midges prefer to lay 

 eggs on the terminal growth of the plant on which they emerge, and 

 particularly on the unfurling tip growth. This is true even in cases 

 150054°— 20— Bull. 833 2 



