NORTH AMERICAN EUCOSMINAE. 33 



Characters as in Eucosma except: 



Fore wing with 10 normally nearer to 11 than to 9 ; no costal fold 

 in male. 



Hind wing with veins 3 and 4 tending to unite and frequently 

 united. 



Male genitalia with harpes without strong anal spine or spines on 

 cucullus ; neck usually with pronounced cluster of hair like spines. 



This genus, while it shows a general advance in venation over 

 Eucosma (veins 3 and 4 of hind wing being frequently united) can- 

 not be regarded as a natural one. Its separation from Eucosma is a 

 convenience and that is about all that can be said for it. Should it 

 be possible eventually to separate the groups in Eucosma on harpe 

 shape and larval characters Thiodia will also have to be broken up, 

 as both pattern and harpe shape show that the forms now listed 

 under the latter have developed from several of the groups of Eu- 

 cosTTia proper. In that case, however, I do not think there will be 

 any associating of species with and without the costal fold. For the 

 present the use of the fold enables division and easier handling of 

 what would otherwise be a most unwieldy group. 



In general shape of the harpes and superficial characters the geno- 

 type differs somewhat from the other species of the genus. The 

 form of genitalia in {loplocama) Thiodia formosana Clemens is 

 much more representative. A drawing of the latter is therefore 

 included to supplement the description. 



KEY TO THE SPECIES OP THIODIA. 



For the following new species, not included in tliis key, see Appendix : sororiana, nepo- 

 tinana, fertoria)ia, modlcellana, and festivana. 



1. Fore wing with a dark basal patch slanting inward from dorsum to costa__2 

 Fore wing without basal patch; or if present not slanting inward from 



dorsum 5 



2. Ground color of fore wing pure white 3 



Ground color of fore wing dirty grayish white (54) scalana. 



3. Basal patch and outer fascia of fore wing pale olivaceous gray 4 



Basal patch and outer fascia golden or copper yellow — (53) octopunctana. 



4. Cilia of fore wing red brown (51) artemisiana. 



Cilia of fore wing olivaceous, faintly dusted with blackish fuscous. 



(52) infimbriana. 



5. Fore wing with a median longitudinal white streak 6 



Fore wing without such 16 



6. Extreme costal edge of fore v/ing from base white, and on basal half un- 



marked 7 



Extreme costal edge not v,'hite from base ; or if so, basal half faintly strigu- 

 lated with fuscous 12 



7. A dark spot or dash interrupting the longitudinal white costal streak at or 



just beyond middle 9 



White costal streak continuing uninterrupted to outer third where it joins 

 first pair of white costal dashes, continuing on thence in a curved double 

 line below costa and fusing with the white costal dashes 8 



