GENE MUTATIONS 



Minnesota, included v/asps with three or four 

 basal segments of antennae decidedly yellow 

 when reared at 30° C. The difference evidently 

 depends upon one gene v/ith various modifiers, 

 determining the' extent of the trait v/hich may 

 be increased by selection. Minnesota yellow is 

 of normal viability and may be regarded as dom- 

 inant since heterozygous females show the trait 

 under standard conditions. (Discarded) 



YELLOW, Y (base of antennae). In February, 1929, 

 two mutant males were found in the offspring of 

 a female that had been treated with X-rays 

 (dosage about 1460 R units) as a four day lar- 

 va. The mutants had the three basal segments 

 of the antennae strikingly yellow. The yellow 

 color is more definitely confined to the three 

 basal segments in this type than is the case in 

 Minnesota yellov/, but lowering of temperature 

 during development induces melanogenesis in 

 both cases. Since heterozygous females show 

 the trait, it may be called dominant. Yellow 

 is fertile in both sexes but of lower viability 

 than wild-type. Distal segments of antennae 

 often appear pale and if temperature is but 

 slightly increased over standard, yellow wasps 

 become deformed and often die in cocoons. This 

 is not the case with Minnesota yellow in which 

 viability is normal (P. W. Whiting, 1932a). 

 (Discarded) 



FUSED, fu (antennae and tarsi). A single male 

 was found in February, 1929, with antennal seg- 

 ments fused together and with tarsal segments 

 lacking or fused together (Fig. 8). The wing 

 of fused (Fig. 7) has a very characteristic and 



55 



