RESTRICTION OF THE GENUS GELECHIA— BUSCK 565 



Chambers Mith the genotype of GeUchia, the European rhombella; 

 hosqueUa^ however, differs from Gelechia in other venational charac- 

 ters and on the basis of genitalia structures belongs to a quite differ- 

 ent group, for which Meyrick has erected the genus Stegasta, the 

 type of which is the Indian species varlana Meyrick. For com- 

 parison the striking genitalia of this genus are figured (pi. 63, fi«Ts 

 26, 27; pL 70, figs. 60, 61). 



The genus Bryotropha Heinemann, sunk by Meyrick as a synonym 

 of Gelechm, owing to the supposed lack of stable venational charac- 

 ters to differentiate it, although retained by the continental European 

 workers, proves to be very distinctly defined by the genitalia, as 

 already shown by Pierce and Metcalfe \ and its validity is further 

 emphasized by the venation and by the single bristle on the basal 

 antennal joint, a character that does not seem to have been recorded 

 before, apparently havmg been overlooked; it is a remnant of a 

 pecten, which is very significant and unusual in the family 

 Gelechiidae, shared only by very few genera, like Sitotroga and 

 Pectinophora^ from which Bryotropha is widely separated on other 

 characters. 



In Aroga, which was mainly founded on the separation of veins 

 3 and 4 in the hind wings, it is found that this character varies 

 within closely allied species and even in the sexes of the same species. 



Like the geneiic charactei-s in venation and labial palpi, certain 

 characters of the genitalia are found not to be absolute. Nature does 

 not conform with artificial synoptic tables, and these must be used 

 with discretion and with an intimate knowledge of allied forms as 

 well as of the group under study. Thus the signum of the female 

 bursa is absent in some species that are clearly referable on all other 

 characters to genera where the signum normally is present. This 

 absence in isolated species of a character present in closely related 

 species is as difficult to explain as is the purpose of the character 

 itself, but numerous examples of such absence in widely separated 

 families lead to the opinion that the absence of this character is not 

 necessarily of generic significance and that the exception to the rule 

 does not disprove the rule, as we are able to conceive it. Similarly it 

 is found that characters of the male genitalia, which normally are 

 remarkably constant and dependable in the separation of genera, are 

 found in certain genera to be variable, even within the species. Thus 

 while symmetry and asymmetry of the genitalia are not normally 

 found within the same genus, both occasionally do occur as variations 

 within a single species, as for example in the genus Chionodes, which, 

 therefore, must be defined on other more stable genitalic characters. 



» Genitalia of the tineid families of the Lepidoptera of the British Islands, 1035. 



