RILEY NOTES ON THE YUCCA BORER. 339 



of similarity of habit ; and I give it as my emphatic opinion that 

 Tuccce is a large-bodied Hesperian, which, though approaching 

 the Castnians through Synemon, has no real relation with them. 

 In certain marked characters it departs from the Hesperians as at 

 present understood, and the only question which a careful study 

 of the species gives rise to in my mind is — not whether it should 

 be considered a Castnian, but whether it offers charactei's that 

 necessarily separate it from the Hesperians. Families should, I 

 think, be made as comprehensive as possible and not unduly mul- 

 tiplied ; and in considering aberrant forms, the objects of classifi- 

 cation are best subserved by retaining them in whatever division 

 can claim the balance of characters. It is better to widen than 

 to restrict in the higher groups. LeConte does better service in 

 bringing Platypsylla among the Coleoptera than does VVestwood 

 in creating a new Order — Achreioptera — for it. Phylloxera, in 

 Homoptera, is much more wisely retained in the Aphididae than 

 made the type of a new Family. Let Yucca, therefore, be re- 

 tained in Hesperidas. By its aberrant characters it may constitute 

 the type of a third tribe, for which I would propose the name 

 Castnioides. This Tribe consists at present, in addition to 

 Megathymzis yuccce, of two other good species, the one from 

 Mexico, the other from Costa Rica. It is very probable that 

 this number will be greatly increased as we become more 

 familiar with the Lepidopterous fauna of Mexico and Central 

 America, where the Yuccas and Agaves abound ; for I have lit- 

 tle doubt that the last-named plants will also be found to nourish 

 other species of the Tribe. 



I have reared from the Yucca Borer eleven Tachnia flies, all 

 belonging to the species which I have designated anonyma, and 

 which infests the larvae of a number of other Lepidoptera.* The 

 fact that Tuccce is attacked by such a parasite is further proof that 

 it is more or less an external feeder, since it is hardly probable 

 that the parent Tachina would enter the burrow, and I know of 

 no genuine endophytes that are similarly attacked. 



4th Mo. Ent. Rep., p. 129. 



