THE PARASITIC WASP, HADROBRACON BREVICORNIS. 45 



(b) The Orange Mutation. On March n, 1920, a female, in 

 all respects typical, was isolated as a virgin. Her progeny 

 consisted of 253 black-eyed males and i male with orange eyes. 

 This mutant occurred in the first bottle in which the mother had 

 been kept for a period of seven days. The count from this 

 bottle on March twenty-seventh numbered 46 including the 

 mutant. The cultures were at that time developing in the 

 incubator at thirty degrees centigrade at which temperature 

 the period from oviposition to eclosion is about ten days. The 

 mutant may have emerged a few days before the count was made. 

 In any case the egg from which he came was laid within the first 

 seven days of the adult life of the mother which lived until 

 April i. The mutation may have occurred during the develop- 

 ment of a single egg; at least it could not have taken place many 

 cell generations before maturation. 



The compound eyes of the mutant were rather light orange. 

 They became slightly darker with age. He was kept alive 

 until May tenth and was mated to various females. "Orange" 

 eyes as they have appeared in later generations are not neces- 

 sarily orange. They are found to vary from very light cream to 

 deep red and from yellowish orange to pink. No trace of a black 

 fleck such as occurs in the eye of Drosophila has been found. 

 The peripheral ommatidia appear black, but this is due, as 

 sections show, to black pigment in the underlying and adjacent 

 integument. Black pigment is also entirely lacking from the oc- 

 elli, although here again it occurs in the adjacent integument. I n 

 the typical wasp the eyes, both compound and simple, are always 

 jet black. Variations in orange are not considered in the present 

 paper which is concerned only with the difference between black 

 and orange. 



(c) Sex-linkoid Inheritance of Orange. The mutant was crossed 

 successfully with six black females and offspring were reared as 

 follows : 



Culture No. Black Males. Black Females. 



178 81 94 



179. ... .49 6 5 



180 73 8 7 



182 39 68 



183 162 67 



185 _i _a 



Total. 6. . 405 383 



