130 BULLETIN 132, UNITED STATES NATIONAL MUSEUM 



without the lobe. As far as identification goes there is little diffi- 

 culty. There is no such uncertainty^ about the lobe as there often 

 is, for example, about the costal fold in other groups. It is either 

 present and fully developed or absent (that is, the elongated, folded 

 structure, not the mere chitinized ridge at inner angle). ^" Specific- 

 ally the group presents more difficulty. Many of the species are so 

 variable in color and, differ so slightly in structure (especially those 

 of Group B) that it is a hard problem to define their specific limits* 

 To add to the difficulty most of them have a number of food plants^ 

 and many have common hosts. The trouble probably is that we are 

 recognizing too few or too many species. If the former is the case 

 then we are allowing too slight a range for structural variation. 

 Careful and extensive rearings from known parents Avill have to be 

 made before we can be really sure of our species. 



The larvae as far as known are all leaf tiers, webbing together the 

 terminal leaves into a rather compact tie and feeding upon the en- 

 closed leaves and buds. Some of the species, especially those at- 

 tacking the berry-bearing plants (strawberry, raspberry, etc.), are 

 of economic importance as enemies of cultivated plants: but none has- 

 ever been recorded as an especially serious pest. 



For convenience of identification I have divided the genus into 

 three groups according to the arrangement of spine group, Spc^^ on 

 the harpe of the male genitalia, as follows : 



Group A. — Spine group, Spc^, upon a digitus projecting from 

 neck of harpe near sacculus. 



Group B. — Spine group, Spc^, upon a digitus projecting from neck 

 of harpe near cucullus. 



Group C. — Spine group, Spc^,, not upon projecting digitus. 



The chief structural differences between close species are in the 

 strength, number, and grouping of the spines of spine groups Spc^ 

 and X on the harpes of the males and in the shape and chitinous de- 

 velopment of the genital plates of the females. These differences are 

 often slight. There is, however, little or no asymmetry in any given 

 species and the characters seem to be good. I do not attach any 

 great importance to the presence or absence of the signum. When 

 present it is very weak, often nothing but a vestigial patch which 

 might easily disappear within the limits of any given species. 



As photographs of male genitalia show very little in this group^ 

 only a few, representing markedly different forms, are given here. 

 A caution is also necessary in connection with the drawings of the 

 harpes (pis. 14, 15, 16, 17, 18). These are accurate as far as struc- 



^ The one possible exception (Olethreutes arcuella) to the contrail notwithstanding, 

 Walsingham states (Ann. Mag. Nat. Hist., ser 7, vol. 6, 1900, p. 128) that Japanese and 

 Korean species possess a short lobe, lacking In European examples. 



