On Certain Grass-Eating Insects. 83 



closely related to C. luteolellus and can be separated only on the 

 form of the scaphium, the form of the other organs being almost 

 identical. Its dark color places it in this division and from this 

 form the others are readily derived. 



3. Crambus interminellus. This species is more specialized 

 than the preceding as is shown by the narrower fore wing and by 

 the larger size. The antennae are somewhat specialized, the 

 joints in the male becoming shorter and broader, while in the 

 female a large seta has been developed on each joint ; in both 

 sexes the setae upon the edge are shorter and finer than in the 

 preceding species. The clasps retain the more primitive form 

 but have become firmly anchylosed at the base, and an accessory 

 spine has been developed. The genital plate is smooth and oval 

 quite different from that of C. caliginosellus, showing that the 

 species did not come directly from C. caliginoselhcs but in all pro- 

 bability from a more primitive form. 



4. Crambus hulstellus. In this species the narrowing of the 

 fore wing has been carried to a much greater extent and the veins 

 branch much farther from the base of the wing. The female 

 antennae exhibit a degree of specialization while the male anten- 

 nae are highly specialized. The clasps depart somewhat from the 

 primitive type and are not firmly anchylosed. This departure 

 from the type seems correllated with a lightening in color and a 

 greater distinctness in the markings. The uncus has become 

 somewhat shortened and a distinct hook has been developed. 

 The genital plate, though more specialized, shows a close relation- 

 ship to C. caliginosellus. 



5. Crambus mutabilis. Though the fore wings are broader 

 than in the two preceding species, this insect is the most highly 

 specialized of the division. The broadening of the wing, in this 

 case, is a secondary development, and has followed as a conse- 

 quence of the highly specialized male antennae. When the an- 

 tennae became so efficient probably the wings became of secondary 

 importance and consequently the process of narrowing stopped 

 and a retrogression began. In due time the same thing will prob- 

 ably occur 'in C. Imlstellus. The valve has retained its more 

 primitive form, but the harpe has been reduced to a very efficient 

 spine. Correlated with the efficiency of the harpe, a reduction 

 of the uncus has taken place. The two members of the scaphium 



