148 PROC. ENT. SOC. WASH., VOL. 23, NO. 6, JUNE, 1921 



rarely strongly chitinized (ex. some species in Epinotia). They are occasionally 

 more or less fused with gnathos (ex. some Olethreutidae) and are frequently rudi- 

 mentary or absent (ex. Laspeytresia). 



Gnathos (Gn). 



The gnathos is a paired organ, ventral to the anus, arising near the base of the 

 uncus below the soci if the latter are present and consisting in its completeness 

 of two lateral arms and a ventral plate (Vp). The arms may be tree, more or 

 less tentile and hairy (ex. Sparganothis^ Synnoma). Much more commonly they 

 are fused at their tips into a strongly chitinized, smooth hook or beak-like struc- 

 ture (ex. Cacoecia, Gelechia), or into a variously modified and ornamented knob 

 (ex. Co/eophora, Depresparia). Occasionally the joined arms are reduced to a 

 mere band (ex. Holcocera). The ventral plate (Figs. 2, 3) if present, is situated 

 in a median line immediately below the anus and is more or less fused with the 

 arms when these are present. It may be a broad shield-like structure (ex. Pe- 

 ronea) or a narrow chitirious strip along the under side of the alimentary canal 

 (ex. Pyrausta, Cerosloma). It is sometimes greatly developed and apparently 

 free lying against and covering much of the anal tube; in which case the arms 

 themselves may be absent. It is often absent or not to be differentiated as a 

 distinct part. 



The gnathos is subject to very great modification. Rarely it is entirely ab- 

 sent (ex. Amorbia, Coelostathma). 



Tegumen (Tg). 



The tegumen is really the entire external covering of the 9th and 10th seg- 

 ments which have not been differentiated in the foregoing 8 parts and from which 

 these 8 parts originate as specialized sclerite structures; but specifically it is rec- 

 ognized as the chitinized dorsal part, articulating at its lower extremities with 

 the vinculum and from which arises the uncus, soci and gnathos, the other parts 

 being normally membranous. This chitinized part of tegumen has been con- 

 sidered by many as the tergite of the 9th segment continued ventrally in the 

 vinculum which is recognized as the sternire of the 9th segment. In certain 

 isolated forms a suture just below the base of uncus would seem to substantiate 

 this view; but the structure is normally so fused that it is impossible to differ- 

 entiate two distinct parts, and we are inclined to consider the entire chitinized 

 tegumen as part of the 10th segment; the 9th segment being greatly reduced 

 and continued dorsally as membrane only. 



In several groups the 8th abdominal segment is more or less modified and ap- 

 parently a part of the genital apparatus, either as a specially chitinized covering 

 (ex. Gelechia) or forming a lobed and strongly haired structure closely associated 

 with the genitalia proper (ex. Pandemis). 



In his presidential address before this society in 1914 the 

 senior author gave in outline the progress of the classification of 

 the Micro-Lepidoptera up to that time and showed how it had 

 culminated in a comprehensive and natural system based 

 fundamentally on venation as conceived and elaborated by 

 Meyrick, who brilliantly utilized the foundations laid by Heirrich- 

 Schaefer. 



It was even then realized that while venation is the funda- 



