220 THE AMERICAN NATURALIST [Vol. LVI 



The compound scute scute-2 females are either some- 

 what intermediate between the two, or they may look en- 

 tirely like one or the other component. On the whole, 

 they are more apt to resemble scute-2 than scute. 



Origin. — From a normal female mated to a scute male, 

 the following types of offspring were obtained : males — 

 one half mormal, one half scute-2 ; females — one half 

 normal, one half somewhat intermediate between scute 

 and scute-2. From this it was concluded that the parent 

 female was heterozygous for the new character and that 

 this character was allelomorphic to scute, a conclusion 

 subsequently verified by direct tests. Six sisters of this 

 female were also tested and none gave scute-2. 



3. Scute-3 (5C3) 



Description. — Scute-3 is an allelomorph of scute and 

 scute-2. All four scutellar bristles, the two sterno-pleural 

 bristles, and a varying number of head bristles are ab- 

 sent. On the head, all three pairs of orbitals are usually 

 missing, and occasionally some of the others are gone. 



The compound females involving scute-3 and scute-2 

 are more apt to be like scute-3 than like scute-2, although 

 in general they are intermediate. Such females could be 

 distinguished from the homozygous scute-2 females in all 

 the cases observed by the absence of at least one sterno- 

 pleural bristle and generally by the absence of all scutel- 

 lar bristles. Scute-3 males are sterile. 



Scute-3 strongly resembles the scute of melanog aster. 

 In both cases scutellar and head bristles are affected. 

 Two stocks of melanogaster scute kindly examined by 

 Dr. Sturtevant agree with scute-3 in lacking scutellar 

 bristles and orbitals, and in having small ocellar bristles. 

 They both possess post-orbitals, however, and one stock 

 occasionally shows the middle orbital present. The other 

 usually lacks the postverticals. 



Origin. — Scute-3 was first observed in the offspring of 

 an F2 female from a cross of a scute female from stock by 

 two rough rimmed stump males. This female seemed to 



