A MUTATION IX THE MOTH-LIKE FLY. 



After eight days the larva becomes quiescent and pupates, 

 spending two days in the pupal stage. The chitinous coverings 

 become more extensive during this time and much darker, 

 (-]..< ially over the head and the thorax (Fig. 3). The Malpighi.m 

 tubule- become shorter and the reddish brown pigment in them 

 becomes -mc\\ hat darker (Fig. 3, M.P.T. . I hiring the pupal 

 ompound eyes, each containing about -eventy- 

 li\e facets, develope. The same reddish brown pigment that 

 urs in the ocelli and in the Malpighian tubule- also dc\elope- 

 in the; of the compound eyes. The chitinous walls between 

 the facets become darkly colored but only after the re<l<li-h 

 brown pigment of the facets is thoroughly established. 1 hiring 

 ilie formation of the compound eyes the ocelli degenerate. 



The adult emerges as an extremely hairy inject \\iih pigment 

 piv-ent in three forms. The compound eyes (Cl - -. j .md 5 ' 

 and the Malpighian tubules (Fig. 4, M.P.T.) contain the reddi-h 

 broun pigment first observed in the larval ocelli and Malpighian 

 inl.iiles. The chitinous covering of the body i- colored with 

 bioun- (.1 various degrees of intensity and the hair- \\hich o>\er 

 i he body and the wings range in color from \\hiie to bn>\\n and 

 Ma. k. Fspecially on the wings the color change- of the haii> 

 are so .ibrupt as to give a mottled appearance. Small patches of 

 hair>. coarse and black, and very conspicuous are located at the 

 end- of the wing veins. 



The adult life lasts from two to nine days, depending upon the 

 M-\ and upon the event of copulation. All normal adult- are 

 po-iti\i-l\ phototropic and negatively geotrojtir when they lir-t 

 emerge bnt become noticeably less sensiti\'e to light and to 

 ^raxity as they grow older. These two reaction- play an 

 import. nit role in bringing the two sexes together for copulation. 

 The adult- are apparently sexually mature at the time of ejiier^in^ 

 and copulation takes place within a few hours. In copulation the 

 male -ei/e- the female uith a pair of heavy terminal forceps. 



II. CHARACTER OF THE Mt i \ii<>\. 



The mutation varies from the normal lly in three pha-e- of it- 

 structuie and in it- reaction to light. All these difference- may 

 be traced to a -ingle scource, namely, the l.ick of tin- reddi-h 

 l>io\\n pigment in all of those structures in which it ordinarily 



