Co7'relation of Structure a7id Host-Relation 179 



basis for the first of the prerequisites — that of systematic classi- 

 fication from structure alone. 



For the second, knowledge of host-relations, we have 

 Mayr's table and the extensive rearings and notes of the Divi- 

 sion of Entomology of the U. S. Department of Agriculture, 

 which my chief, Dr. C. V. Riley, permits me to use for this 

 purpose, as well as his own personal notes made mainly ini 

 Missouri prior to 1876. In all these comprise more than 200 

 rearings and of the 150 species in the National Museum collec- 

 tion, about 120 have been reared and the host-insect identified 

 with sufficient accuracy for our present purpose. 



lyCt us see then how far uniformity of habit goes in this 

 group, by taking up one after another of the described genera : 



Rhoptis Forster. — European : — Coccus racemosus. 

 American: — Pseudococcus aceris, (111.) Dactylopius ephedrae (Cal.) 



Holcotliorax Mayr. — European : — Lithocolletis 5 spp., Tischeria com- 

 planella, Nepticula spleudidissimella, Hyponomeuta 4 spp., Plusia 

 nioneta. 



Aphyctcs Mayr. — European : — Coccidae 9 spp., nearly all Lecaniinas. 

 American : — Lecanium, gspp., (Mo., S. C, Ala., Cal., Va., Oreg. Fla.) 

 Dactylopius, 2 spp., (Cal.) Ceroplastes, 2 spp., (Ariz., N. Mex.) 

 Kermes i sp., Pulvinaria iunumerabilis, (la.) Diaspis rosae, (N. 

 J.) Mytilaspis citricola, (Fla. ) 



Blastothrix Mayr. — European : — Coccidae, 9 spp., mainly Lecaniinae. 

 American: — Lecaniuni, 4 spp., (N. Y., Cal., Fla.), Pseudococcus 

 yuccEE (Cal.) 



Psilophrys Mayr. — European : — Lecanium sp. 



Leptomastix 'Fc&rst. — American : — Dactylopius destructor, (D. C.) 



Copidosoma Ratz. — European : — Agrotis fumosa, Hadena polyodon, L,eu- 

 cania albipicta, Plusia 5 spp., Catocala electa, Geometra, Cidaria 

 variata, Eupitliecia 4 spp., Tortrix sp., Carpocapsa splendora, Hy- 

 ponomeuta 2 spp., Cerostoma sp., Depressaria 2 spp., Gelechia fa- 

 vilaticella, Lita alsinella, Tachyptilia populella, Coleophora, 2 spp. 

 American : — Papilio turuus, (W. Va.) Celaena renigera, Plusia bras- 

 sicae, (many states.) Aletia xylina, (Ark.) Acronycta sp., (Mo.) 

 Unknown Noctuid larvae, 3 spp., (Colo., Ont., Quebec.) Sericoris 

 coruscana, (N. H.) Gelechia gallgesolidaginis, (Mo.) G. pseudaca- 

 ciella, (D. C.) G. gallaeasterella, (N. J.) G. sp. (Ala.) G. viburuella, 

 (Mo.) G. epigaeella, (Va.) Tinea granella, (D. C.) Bucculatrix 

 thuiella, (Mo.) Coleophora sp., (D. C.) Lithocolletis fitchella, (D. 

 C.) Unknown Tineid larva, (Mo.) 



