OF WASHINGTON, VOLUME XI, 1909, H5 



NOTES ON THE FAMILY >EGERIIDyE (SESIID/E), WITH 

 A SYNOPTIC TABLE OF THE NORTH AMERICAN 

 GENERA. 



| Lcpidoptera, .'Hj>xriid;c. \ 



BY AUGUST BUSCK. 



The character which has been relied upon* to distinguish the 

 family ^-Egeriidae, namely, the absence of vein 8 in the hind 

 wings, proves to be an illusion. The apparent ease with which 

 the venation can be studied in the more or less transparent 

 wings of this group of moths has probably occasioned the 

 error, but if careful slides are made of softened and denuded 

 wings, it is plainly seen that the normal eight veins are really 

 present in all the genera, though veins 7 and 8 are sometimes 

 partly coalescent. 



The mode of attachment between the fore wing and the hind 

 wings in this family is peculiar and has added to the difficulty 

 of interpreting the venation rightly. Aside from the frenulum, 

 which normally, though not invariably, f is single in both sexes, 

 the hind wing has a narrow, sharp, upward fold along the costa, 

 into which the downwards-folded dorsal edge of the fore wing 

 fits snugly and securely. Anyone who has spread moths of 

 this group must have noticed how easy the task is, if the speci- 

 men is fresh and soft. By merely guiding the fore wing up into 

 position the hind wing follows along; but if once the two wings 

 arc separated, it is exceedingly difficult to get them into their 

 natural relations again and a poor mount results. This is be- 

 cause the fold on the hind wing is elastic and is difficult to 

 wedge open again if the edge of the fore wing has slipped out. 

 This fold locks the long, thin wings together very effectually 

 and enables the strong flight of these moths. 



If a pair of wings of a dry, well-mounted specimen is placed 

 on a slide il is practically impossible to separate them without 

 injury to the wings, except by sliding them longitudinally away 

 from each other. 



When this fold on the hind wing is softened and straightened 

 out in a slide-mount the costal and subcostal veins are both 

 observable. 



A similar, though not quite so strongly developed, arrange- 

 ment for holding the wings together is found in the Syntomidae. 



There is considerable difference of opinion about the nomen- 

 clature of the family /Egermke (Sesiidse). The writer is in- 



*Mi-yrick. Handbook Brit. Lcp., p. 562, 1895. 



t|'Yni;ik's arc occasionally found with divided frenulum. 



