20 B. C. ENTOMOLOGICAL SOCIETY 



"I have in a sort of way made Hydriomena the refuge of species 

 whose males I have not seen, and whose exact reference cannot there- 

 fore be given. The species under it are yet, in respect to palpi, antennae, 

 and thoracic tuftings, very variable, but I hesitate to make any further 

 divisions, as the bulk of the species lie midway between the extremes." 



This is how the position stood until quite recently, although it has 

 been felt by workers in this group for a long time past that something 

 would have to be done to further limit this unwieldy and cumbersome 

 genus. The true Hydriomenas were easily separable, and fell into a 

 natural group, but what to do with the others was the great trouble. 

 Out of 28 species listed by Dr. Dyar (U.S.N.M. Bull. 52, 1902) in 1902, 

 only 8 were true Hydriomenas. However, in that monumental work, 

 "Seitz Macro-Lepidoptera of the World," parts of which were first 

 published in 1913, and which owing to the war, has never been completed, 

 and perhaps never will be, Louis B. Prout, of the British Museum, the 

 greatest geometridist we have today, and in whose charge the geometrid 

 part was placed, has completely revised the whole of the family, with 

 the result that all those fugitive species which had found a resting-place 

 in this genus, were removed to other genera or else had new genera 

 erected for them. 



In the 1906 Check List of B.C. Lepidoptera, 13 species were listed 

 under the genus Hydriomena, of which only seven were true species of 

 this genus — the other six species have since been placed in four other 

 different genera. 



Having shown you the difficulties we have had to contend with in 

 this group, and brought you down to the point where the true Hydrio- 

 menas have been at last placed by themselves, I will now go on to give a 

 brief resume of these true species. 



Previous to 1911, very little was known about the forms described 

 by the older authors, several of them having been described from females 

 only. In that year Mr. L. W. Swett, of Boston, Mass., published an 

 article in the Can. Ent., Vol. 43. p. IZ et seq., in which he separated them 

 into three main groups according to the length of the palpi — short, 

 moderate and long. This was a distinct advance on anything attempted 

 before, and reduced them from an unwieldy mass into something like 

 approaching order. 



In the new Check List they are placed practically as Swett worked 

 them out, but since then Messrs. Barnes and McDunnough have pub- 

 lished a revision of this group (Cont. N.H. Lept. No. Amer., Vol. IV., 

 No. 1, May, 1917). This revision is based on the structure of the male 

 genitalia, with special reference to the shape of the uncus, and has 

 certainly led to a number of radical changes. The authors have retained 

 Swett's palpal subdivisions, so that with taking these two principal char- 



