On Certain Grass-Eating Insects. 87 



triangular form of C. decorellus. At the base of the valve there is 

 a short flattened spine. The harpe has become highly special- 

 ized at the tip, there being on its mesal surface many short 

 chitinous spines. The uncus has become reduced to a slender 

 spine, while the lower limb has suffered little reduction. 



17. Cranibus extorralis. This species has no very close affin- 

 ities among the species studied. The narrow fore wing indicates 

 a high degree of specialization ; all the veins branch near the 

 outer margin of the wing. The antennae are highly specialized. 

 The primitive elongate form of the clasps connects this species 

 with C. luteolellus. At the base of the valve a rudimentary spine 

 occurs and this connects the species with the Unistriatellus 

 Group. At the tip of the harpe a pair of curved spines have 

 arisen. The uncus has been reduced somewhat, though not 

 well shown in the figure. This species stands at what might be 

 termed the head of a straight line of development. 



Siibdivision III. The Agitatcllus Group.— ?\^\.^s III. , IV. , IX. , 

 X., XI., XII., XIV., Figures 18-27, except figure 25. 



This group represents a line of development from forms in 

 which the clasps became broadly and equally developed before 

 other morphorlogical changes occurred. This group includes the 

 most specialized forms and, as might be expected, great diversity 

 in form occurs in the genital organs. 



18. Cramhis innotatellus. In this species the fore wing is 

 rather broad and the veins are independent. The antennae are 

 not highly specialized. The clasps are broad and nearly equal. 

 Upon the edge of the harpe a row of cbitinous processes has been 

 developed, which terminates in a stout recurved hook. The 

 uncus has been strongly reduced and modified. While the gen- 

 italia exhibit considerable specialization, it is what might be 

 termed a sidewise development, and from the ancestors of this 

 form, or a closely allied species, the next two species have arisen. 

 The genital plate has been strongly modified. 



19. Crambiis topiarius. The broad fore wing and the inde- 

 pendence of most of the veins stamp this species as more general- 

 ized than C. albelbis. The male genitalia are similar. In each 

 the haroe has been reduced very much. The valves are broad, 

 flattened and convex mesally, but in C. topiarbis a tuft of very 

 long hairs has been developed at the base of the harpe. As a 



