422 ENTOMOLOGICAL SOCIETY 



independently in the families Pompilidas and Vespidae, and hence 

 could not be considered affinities. 



A discussion was started by Dr. Gill as to the relative value, 

 for purposes of classification or demonstrating relationship, of 

 structures of distinct value and use to the species as opposed to 

 structural characters of little value and use. He held that the 

 morphological characters exhibited by the more useful organs 

 were least important as exhibiting relationship, for the reason that 

 such characters were most subject to variation, whereas structures 

 of less use and importance were necessarily less subject to varia 

 tion and hence more indicative of affinities. The little value of 

 morphological characters was illustrated by a reference to the 

 classification of the whale as one of the fishes by the ancient au 

 thors, and of much of the old classification which was based on 

 similarity of function rather than on true hotnologies. 



The first paper of the evening was by Dr. Dyar, and was en 

 titled : 



ON THE DISTINCTION OF SPECIES IN THE COCHLIDIAN 

 GENUS SIBINE. 



By HARRISON G. DYAR. 



Some years ago Mr. H. Druce suggested to me that the North 

 American and Mexican forms of Sibine might be of the same 

 species, as they differed only in size. I replied that this might be 

 so, but that the larvae as figured by the old authors differed 

 widely. This is a striking fact in the genus, the practical iden 

 tity of the moths and the great dissimilarity of the larvas. The 

 two species with which I am the most familiar are the North 

 American Sibine stimulea and the South American S. tri- 

 macula* The larvae differ widely as shown by published figures, 

 as I have repeatedly verified. The moths are closely similar. I 

 find that the shade of color is variable and the presence or absence 

 of the small white dots on the wings is a matter of indifference in 

 both. The specific differences narrow to two points only: (i) 

 6". stimulea is generally smaller, the expanse of males being 24 

 to 29 mm., average 26.6 mm. ; of females 31 to 38 mm., average 

 35.8 mm. ; of S. trimacula, males 31 to 34 mm., average 32.5 

 mm. ; of females 39 to 56 mm., average 46.5 mm. (2) The hind 

 wings of stimulea are uniformly dark brown, while those of 



* Hereinafter identified as S.fusca. 



