The above are the only two attempts at a definition of the group 

 which exist. Both contain slight inaccuracies ; Comstock's definition 

 would exclude sniithi Druce, and polingi Skinner, both unknown to 

 science at the time, which have a wing expanse of approximately 

 1% in.; Mabille's statement that the body much exceeds the secon- 

 daries may be true of yuccae but certainly of none of the other spe- 

 cies ; the posterior tibiae are further not tinthout spurs, in all the mem- 

 bers of the group both mid and hind tibiae possess a single pair of 

 short, apical spurs, a fact which was already noted for yuccae by Riley 

 as early as 1876 (Tr. Ac. Sci. St. Louis, III, 333). 



Regarding the supposed affinity of this family to the Castniidae 

 it is a mystery to us how such entomologists as Grote, Butler, and 

 Druce could ever have been led to sustain such a theory. Apart from 

 a slight general superficial resemblance there is really nothing in 

 common between the two families. The Castniidae possess a well de- 

 veloped frenulum, the Mcgathymidae none; in the former family the 

 tibiae are spineless and the posterior ones, as far as we have seen, pos- 

 sess two pairs of spurs ; in the latter family the tibiae are all spined 

 and but one pair of apical spurs is present; the venation is totally at 

 variance, the Castniidae, among other things, having on the primaries 

 two anal veins and a four-branched radius, two of the branches being 

 stalked from the areole ; the Megatliymidac possess a single anal vein 

 on primaries and a five-branched radius, all the branches being separ- 

 ate from the cell. Further points of distinction may be found in the 

 palpi of the Castniids, which are narrow, pointed, and distinctly 

 Noctuid in character, and the antennae which are usually provided 

 with an apical spine and bunch of bristles. 



As to whether the "giant skippers" should be accorded family or 

 sub-family rank is more or less a matter of personal opinion. Most 

 of the leading European authorities, such as Tutt, Spuler, Seitz, etc., 

 appear agreed that the "skippers" form a distinct group by themselves, 

 equal in value to the two great divisions, Rhopalocera and Heterocera, 

 so long in use. Tutt (British Butterflies, Vol. I) gives them super- 

 family rank as Urbicolides or Hcsperiides and personally we are in- 

 clined to agree with him. We have therefore retained the name 

 Megathymidac, as given by Comstock. 



A complete discussion of the family with all its characteristics 

 and affinities must necessarily take into consideration the egg, larva, 

 pupa and imago. Concerning the three first mentioned stages our 



