26 BULLETIN 1426, U. S. DEPARTMENT OF AGRICULTURE 
SEXUAL DEVELOPMENT 
In order to obtain information as to the time of sexual maturity, 
rate of reproduction, and number of generations annually, studies of 
the genital organs (fig. 12) of the root borers were undertaken at dif- 
ferent seasons. 
Examinations of females in the fall seem to prove conclusively 
that there is but one generation in a season. Records of fall exami- 
nations are as follows: September 7, 1915, 10 females showed no egg 
development; 6 males had testes well developed. October 7, 1915, 
2 males and 1 female were. collected from new burrows in clover 
crowns in a field, a strip of which had been plowed in the summer; 
no eggs were found developing in the ovaries of the female. On the 
same date 38 males and 27 females were taken, mainly from dead 
roots; 4 of the females had first traces of egg formation (in one case 
estimated to be one-eighth grown); no others had any indication of 
incipient eggformation. October 7, 1918 (a warm, dry season) , 3 female 
adults were taken from a plant collected and transplanted August 26. 
All of these were contained in burrows in live root tissue; only 1 fe- 
male had any egg development; in this case 3 very immature eggs 
were contained in the ovarian tubes. October 2, 1918, of 6 females 
Fic. 11.—Diagram illustrating life history and seasonal occurrence of the clover root borer 
taken from living roots, 3 contained no eggs, 1 contained two incipient 
eggs appearing as dusky spots, and 2 contained eggs barely visible 
in the ovaries. Of 31 male and 30 female borers collected October 
7, 1918, in dead roots, and examined October 10, only 1 femate had 
any trace of egg development, there being two very small developing 
eggs in the ovarian tubes. Three females were taken October 14, 
1916, from roots in a cage, all of which were reared from a female 
introduced into thecage March 9 (almost a month before the first spring 
flight); none of these daughters were found to have any eggs devel- 
oping in the ovarian tubes. Another female reared under the same 
conditions was found with an incipient egg. 
Males evidently are mature in the fall, as they have been observed 
to mate or attempt mating when brought with females into the lab- 
oratory by the writer and by H. L. Parker, at Hagerstown, October 
16, 1916, and October 6, 1915, respectively. Folsom (12) reported a 
pair, taken from roots in the field, in copulation in a cage in the lab- 
oratory on September 9. On October 3 he found on this plant 
larve, but no eggs, and one of the adults (sex not stated) died 
before November 21. The female in this case may have been a 
belated adult of the previous generation. 
Examinations of the sexual organs of borers during the latter part 
of February, 1916, revealed but 2 females showing egg formation; of 
