FOUNDATIONS FOR SEX 



83 



Iclcs would l»e female determining. By hav- 

 ing a sufficient number of these genes the 

 jiroduction of diploid males would be cur- 

 tailed to a point at which their various fre- 

 quencies could be explained. In support of 

 this liyi)othesis, multiple alleles to the num- 

 ber of at least 9 were found to exist for 

 thi.> single sex locus. 



In principle at least, the honey bee could 

 have the Habrobracon scheme of sex de- 

 termination. Rothenbuhler (1958) has re- 

 cently collected the researches which test 

 this possibility. Tests of the multiple allele 

 hypothesis as applied to the honey bee were 

 made by Mackensen (1951, 1955) who in- 

 terpreted evidence for inviable progeny pro- 

 duced by mating of closely related individ- 

 uals as proof that this species as well as 

 Habrobracon juglandis follows the multiple 

 allelic system. The discovery of male tissue 

 of bii)arental origin in mosaic bees from re- 

 lated i)arents was considered as further evi- 

 dence for the multiple allelic theory of sex 

 determination (Rothenbuhler, 1957). 



Most recent cytologic evidence supports 

 the concept that there are 16 chromosomes 

 in the gonadal cells of the male and 32 in 

 those of the female (Sanderson and Hall, 

 1948, 1951; Ris and Kerr, 1952; Hachinohe 

 and Onishi, 1952; Wolf, 1960». Hachinohe 

 and Onishi (1952) found 16 chromosomes 

 as characteristic of the meiosis in the drone. 

 Wolf observed a nucleus in both bud and 

 spermatocyte of the only maturation (equa- 

 tional) division. 



The greatest progress has been made in 

 understanding the mechanisms of sex mosai- 

 cism in the Hymenoptera species. These 

 mosaics, although ordinarily of rather rare 

 occurrence, have a direct bearing on sex 

 determination and development. In Apis, 

 iiolyspermy furnishes the customary basis 

 for their formation. One sperm fertilizes 

 the haploid egg nucleus and another sperm, 

 which has entered the egg instead of degen- 

 erating as it ordinarily does, enters into 

 mitotic cleavage and eventually forms is- 

 lands of haploid cells of paternal origin 

 among the diploid cells derived from the 

 fertilized egg (Rothenbuhler, Gowen and 

 Park, 1952). Evidence showing that genetic 

 influences affect the sperm nucleus toward 

 stimulating its independent cleavage is 

 found to exist in Apis material (Rothen- 



buhler, 1955, 1958). Tliousands of gynan- 

 dromorphs have been observed in Apis, all 

 but a small number of which have been pro- 

 duced in this manner. This method of initi- 

 ating sex mosaics also exists for Habrobra- 

 con (Whiting, 1943b) but is rather rare. 

 In Habrobracon the frequent mode has a 

 different origin. The gynandromorph is 

 formed from the cleavage products of the 

 normal fertilization of the egg nucleus com- 

 bined with those of a remaining nuclear 

 product of oogonial meiosis. Under these 

 conditions the female tissue is 2N of bi- 

 parental origin and the male tissue is N of 

 maternal origin (Whiting, 1935, 1943b). 

 This type is less frequent in Apis but one 

 specimen has been described by Mackensen 

 (1951). 



A number of other ways in which sex 

 mosaics may occur are occasionally ex- 

 pressed in these species. Three different 

 kinds of male tissue have been observed in 

 individual honey bee mosaics produced by 

 doubly mated queens — haploid male tissue 

 from one father, haploid male tissue from 

 the other genetically different father, and 

 diploid male tissue of maternal-paternal 

 origin. In other cases, the diploid, biparental 

 tissue was female and associated with two 

 kinds of male tissue (Rothenbuhler, 1957, 

 1958) . Cases where the haploid portions of 

 the sex mosaics are of two different origins, 

 one paternal and the other maternal, while 

 the female portion is representative of the 

 fertilized egg, are known in Habrobracon 

 (Whiting, 1943b). Similarly, Taber (1955) 

 observed females which were mosaics for 

 two genetically different tissues and which 

 he accounted for as the result of binucleate 

 eggs fertilized by two sperm. Mosaic drones 

 of yet another type were observed by 

 Tucker (1958) as progeny of unmated 

 queens. They were interpreted as the cleav- 

 age products from two of the separate nu- 

 clei formed in meiosis. These cases represent 

 a number of the possible types that arise 

 through meiotic or cleavage disfunctions 

 under particular environmental or heredi- 

 tary conditions. 



Tucker (1958) studied the method by 

 which impaternate workers were formed 

 from the eggs of unmated queens. For this 

 purpose he used genetic markers, red, char- 

 treuse, ivory, and cordovan. Observations 



