127] LEPIDOPTEROUS LARVAE — FR ACKER 127 



possible here. Many of the characters are adapted from his descrip- 

 tions and a free use has been made of his method of separating the 

 genera. 



On the basis of larval structure the butterflies may be divided into 

 about five groups. In the Hesperioidea, including the Hesperiidae and 

 Megathymidae, the crochets are triordinal and arranged in a complete 

 circle, and the body bears very short numerous secondary setae but no 

 other form of armature. The larvae of the Lycaenoidea (the Lycaenidae 

 and Riodinidae) are somewhat onisciform in shape, the head small and 

 retractile, the body covered with coarse secondary setae. Forbes has 

 called attention to the peculiar form of the prolegs, which bear an in- 

 terrupted mesoseries of crochets with a spatulate fleshy lobe arising 

 near the interruption. The Papilionidae and Parnassiidae are charac- 

 terized by the presence of prothoracic osmateria ; in the former the body 

 is practically without setae, but both secondary setae and verrucae are 

 present in the latter. The Pieridae are considered by many as belonging 

 to the Papilionoidea but the larvae are not closely related. All the 

 remaining families, Libytheidae, Lymnadidae, Ithomiidae, Heliconiidae, 

 Agapetidae, and Nymphalidae, may be grouped together as Nymphaloi- 

 dea, altho they have few larval structures in common. They are all 

 armed with scoli or fleshy filaments or a bifurcate suranal plate, except 

 the Libytheidae, which are distinguished from the others by the pseudo- 

 circular arrangement of the crochets. 



Family Hesperiidae 



The conspicuous structure of the larvae of skippers is the large head 

 attached to a strongly constricted "collar". This head is covered with 

 numerous secondary setae, often plumose but never long, sometimes 

 borne on chalazae. The labrum is shallowly concave at tip and usually 

 a shallow mesal groove is present on the cephalic surface. The front 

 extends about two-thirds of the distance to the top of the head. 



The body is either cylindrical or fusiform, widest at the proleg- 

 bearing segments, usually tapering considerably toward each end ; sec- 

 ondary setae numerous, often very short; small flattened plates some- 

 times present, possibly showing position of primary setae ; segments 

 divided into indistinct annulets, incisions all shallow or obscure; pro- 

 thoracic shield narrow, often indistinct. Prolegs with triordinal crochets 

 in a complete circle. 



Scudder divides the family into Hesperidi and Pamphilidi and 

 gives a table for the separation of the genera of the former group in 

 all stages. The family is so poorly represented at the National Museum 

 that at present nothing can be added to his work. 



