THE GENETICS OF HABROBRACON JUGLANDIS ASHMEAD 



pects because of unfavorable cultural conditions 

 (very low humidity) or inadequate nutriment of 

 females (feeding v/ith honey instead of caterpil- 

 lar juice) v/hile females of certain genetic 

 types lay v/ithered eggs of irregular form. Non- 

 hatchability may then be the result of non-nu- 

 clear causes, recessive lethals, dominant le- 

 thals, or male-producing fertilization (P. W. 

 Whiting, 1938a, b) . 



Dominant lethals may be induced in the sperm 

 of Habrobracon by X-radiation of the males. At 

 10,000 to 20,000 R units all sperm have at least 

 one lethal. With very high dosages, 41,000 to 

 142,000 R units, some sperm are directly inacti- 

 vated while many still remain active and able 

 to carry dominant lethals into the eggs (P. W. 

 Whiting, 1937a, b). Neutrons have also been shown 

 to produce dominant lethals (P. W. Whiting, 

 1936), being actually much more effective than 

 X-rays. Ultra-short (1 meter) radio waves ap- 

 pear to be ineffective (P. W. Whiting, i937a,b). 



Biparental males have been obtained (Stancati, 

 1932; Bishop, 1937) after X-radiation of sperm 

 from related males, but the data are not suffi- 

 cient to indicate their decrease. X-radiation 

 of sperm from unrelated males has never resulted 

 in biparental males. Experiments from crosses 

 with closely related males (treated and untreat- 

 ed) indicate that while the number of haploid 

 males produced per day is not changed by X-radi- 

 ation of sperm, both kinds of biparental off- 

 spring (males and females) are decreased with 

 increasing dosages and that they are decreased 

 at approximately the same rate. This indicates 

 that X-radiation of sperm fails to modify the 

 type of fertilization and that the changes in- 



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