THE PARASITIC WASP, IIADRORRACON BREVICORNIS. 5! 



DISCUSSION. 



(a) Sex-linkoid Inheritance in the Honey-bee. Johannes Dzier- 

 zon (1845) based his theory of the parthenogenetic origin of 

 drones of the honey-bee, in part at least, upon crosses of various 

 races. Clear evidence of sex-linkoid inheritance in the bee has 

 been recently furnished by Newell (1914) who crossed a yellow 

 Italian queen to a gray Carniolan drone. All the offspring were 

 yellow. The reciprocal cross produced yellow females and gray 

 males. Heterozygous females produced yellow and gray drones 

 in equal numbers. 



Many investigators have crossed Italian bees to the black 

 French or German forms. Sex-linkoid inheritance appears to 

 be the rule here also but there are numerous apparent exceptions. 



Perez (1879) crossed yellow Italian queen to black French 

 drone and examined three hundred drone offspring. Forty-nine 

 showed markings interpreted as of paternal origin. 



Cuenot (1909) crossed black female to yellow male and ob- 

 tained females, all of which had yellow bands; three hundred 

 black males; twelve males with small amount of yellow; and 

 two males with broad yellow bands. 



Inasmuch as drones intergrading between black and yellow 

 occur it is natural to suppose that there is more than one factorial 

 difference between the tw r o races. It has been suggested that 

 those males which were apparently more or less patroclinous 

 might have arisen from eggs laid by hybrid workers, or that the 

 queen might have been of mixed origin. It may be, however, 

 that the intergrading drones were mosaics, comparable to the 

 mosaic males of Hadrobracon. 



(b) Sex Determination and Parthenogenesis. In most animals 

 there appears to be a sex-difference in chromatin content. This 

 varies, from a theoretical minute portion of one chromosome to a 

 clearly visible difference of one or more chromosomes. In the 

 case of haploid parthenogenesis, the male has the haploid number, 

 and reduction of the egg nucleus takes place in a normal manner. 

 This occurs apparently in at least most of the Hymenoptera, in 

 the white fly (Stoll, 1919; Schrader, 1920) and probably in 

 several other forms. Diploid parthenogenesis occurs in many 



