On Certain Grass-Eating Insects. 85 



in C. vulgivagellus. The two members of thescaphium are short 

 and nearly sickle-shaped. The genital plate is quite irregular. 



9. Craynbus vulgivagellus. The narrower wings and the 

 greater development of the labial palpi indicate a higher degree 

 of specialization than in the preceding. The antennae are also 

 more highly specialized. The harpe has been more reduced, but 

 in other respects the genital organs are almost identical. 



The Unistriatellus Group. — Plates II., VII., XII., XIII. .Figures 

 10-13. The valve has nearly the same form as in C. decor ellus, 

 but it is more irregular. The harpe has become a stout recurved 

 hook in C. unistriatellus but in the other species the harpe is more 

 reduced. There has been developed at the base of the valve an 

 accessory spine. This group was probably separated from a species 

 closely allied to C. decorellus. In the Decorellus Group speciali- 

 zation has reduced the eflficiency of the harpe and left the uncus 

 comparatively unmodified. In this group the harpe and the ac- 

 cessory spine have become very eflScient, while the uncus has 

 become very slender. The uncus seems to be exactly alike in the 

 four species of this group. 



10. Crambus unistriatellus. This is the most generalized 

 species of the group. In the fore wing none of the veins have 

 become coalesced and the wing is broader than in the other 

 species. The harpe in this group gives no reliable character for 

 separating the species. In this species the harpe is strongly re- 

 curved and there are three recurved chitinous hooks on the penis. 

 The genitalia show a high degree of specialization in some ways 

 but the wings place this species as the most generalized. 



11. Crambus leachellus. The fore wing is narrower than in 

 the preceding and vein V, and vein V^ have coalesced at the base ; 

 this has also occurred in the remaining species of this group. 



12. Crambus hastiferellus . The narrowing of the fore wing 

 and the coalescense of vein V, and vein V, has been carried still 

 further. The genital plate is more specialized than in C. leach- 

 ellus. 



13. Crambus prcefectellus. This is the most specialized of the 

 group as is seen by the still narrower fore wings. 



The Giradellus Cro2ip.—Y\2XQ.s II., IV., VIII., X., XIII.. 

 XIV., Figures 14 and 25. 



14. The two species included in this group are highly specialized 



