588 BULLETIN UNITED STATES GEOLOGICAL SURVEY. [YoI.Xl. 



usual, ia a multiform and plastic group, liketlie Bomhyces, whose blood 

 we can trace in groups like the Glaucopidians, which we now separate 

 from them, the differeuce having grown to be a large one, we shall find 

 more clearly proofs of such a condition of groups of individuals. I pro- 

 pose to call them Frogenera. An exami^le is, for instance, Dutana; 

 also Ichthyiira, Nadata, Clisiocampa, Orgyia (and Uucronia as a division 

 of Semileuca, if we are obliged to admit Neumcegeni into Heniileucaj as 

 I believe). Other instances will occur to the student. The siiecies of 

 such Progenera stand in a nearer connection than usual ; with some of 

 the forms the interbreeding may not have become suspended. In the 

 butterflies Grapta and Basilarchia (I use this term for the American 

 Bros, Arthemis, Proserpina, Ursula, Bissippus, excluding the Californian 

 forms, and thus, perhaps, as a division of Liminitis) are instances of 

 Progenera. Subgenera are smaller assemblages of species in a genus, 

 agreeing in some minor peculiarity of structure. They, are not groups 

 of coincident forms varying less among themselves than is the rule with 

 " species," while yet not "varieties," being more distinct and true. In 

 the study of such groups, particularly in that of Basilarchia, as I have 

 elsewhere pointed out, lie immense possibilities in the direction of as- 

 certaining the causes of so much diversity in the Lepidoptera. 



INSECTS INJURIOUS TO VEGETATION. 



Eugonia snbsignaria Hiibner. 



This whitish Geometrid used to be so common in Brooklyn, when I 

 went to school there in 1857 and subsequently, that the horse-chestnuts, 

 elms, and maples, the latter especially, became completely defoliated, 

 and the brown measuring worms used to hang down and cover the 

 sidewalks, ultimately to the great discomfort of the passers by. 1 have 

 seen ladies come into the house with as many as a dozen of the worms 

 on their skirts and crawling over their clothes. ]S"ervous persons were 

 much frightened in discovering the disagreeable-looking but harmless 

 caterpillar on their garments. At the same time the worms of Alypla 

 S-macitlata and Tkyreus Abhotii were very common on the grape vines. 

 Also the larvce of Beidamia inscripta, Eudryas unio, and Chamyris cerin- 

 thaweTQ common. In New York, as well, some trees about the old Post- 

 office, on jSTassau street, were similarly affected by the larvre of B. suh- 

 signaria. The advent of the English sparrow changed all this. The 

 naked brown larvffi of subsignaria disappeared before them. Gradu- 

 ally all the other naked larvae became scarce or disappeared. Orgyia 

 leuGOstigma, with its hairy uneatable larvae, became more common. In 

 Buffalo, where this was always common and the naked larvae were rare 

 or unknown, the English sparrow did no good as a destroyer of the 

 caterpillars on the city shade trees. When I lived in Amity street, 

 Brooklyn, about 1859, I remember to have found on our small grape 

 vine, in the contracted back yard to the usual brown-stone house, the 

 larvae of most of the species here mentioned, as well as Bveryx cJioerilus 



