104 THE ENTOMOLOGIST. 



Some of the most difficult problems met with in the study of 

 these genitalia are involved in the striking discovery that our 

 H. nictitans consists not of two species or possibly three, as Mr. Tutt 

 established a considerable time ago, though not perhaps incontes- 

 tably, but actually of four very distinct species, barely capable of being 

 distinguished from each other without reference to the appendages 

 (there is no great difficulty in separating typical English ixdudis and 

 nictitans). An examination of the appendages suggest, nevertheless, 

 that crinanensis, the new species discovered in his researches by Mr. 

 Pierce, belongs not only to a distinct species but that it should be 

 placed in a separate genus. The query then presents itself, Is this a 

 derivative from the nictitans-paludis-lucens forms, or is it by mimi- 

 cry or some other reason approaching them from elsewhere ? We 

 have never quite satisfied ourselves, perhaps from want of proper 

 enquiry, that Pierce's species lucens is identical with nictitans var. 

 lucens. At any rate, lucens, Pierce, is to be found amongst series of 

 simple nictitans in collections, and nictitans var. lucens is very com- 

 monly really nictitans. We have a strong suspicion that nictitans, 

 Pierce, and lucens. Pierce, both have forms that are erronously 

 regarded as respectively nictitans and lucens. We find no discussion 

 of these questions in " The Genitalia." 



We miss also any discussion of the question as to Noctua tliulei, 

 Stgr. {conflua, Tr. ? ). Mr. Pierce mentions conflua as identical 

 with festiva, but says nothing as to what he means by conflua, 

 whether the mainland var. oi festiva, or the distinct or semi-distinct 

 Shetland form. 



It must be recognised that all such questions can only be authori- 

 tatively solved by exploring also the allied species ; only so can the 

 amount of difference necessary to prove specific identity or otherwise 

 be gauged, as, for instance, Everes argiades and alcetas and Guindo 

 minima have appendages that, at first glance, are absolutely identi- 

 cal, but minute, constant differences can be detected that make them 

 clearly three species. On the other hand, Plehius cegon has variations 

 between individuals, even between the opposite clasps of one indi- 

 vidual, that exceed in amount the difference that in the Everids just 

 referred to distinguishes species. 



Mr. Pierce's work will no doubt give an impulse to the study of the 

 genitalia of the Lepidoptera, calculated as it is to give much assis- 

 tance in their study. Though very complete, it nevertheless suggests 

 various directions for further study ; the marvellous structure of the 

 " Vesica " (Pierce), an investigation of the curiously aberrant forms 

 in silago and oxyacanthce, are only a little more obvious than many 

 other points for investigation. — T. A. C. 



Critical Notes on the Classification of the Corduliince, {Odonata). By 



J. G. Needham. Columbus, Ohio, December, 1908. (Annals 



of the Entom. Soc. of America, i. No. 4). 



We have here a system of classification of the genera of the 



Corduliines of the world based on wing-venation. Two diagrams 



explain the terms employed. Students of the Odonata will find this 



short article of much interest, Mr. Needham having been so long 



at work on these insects. — W. J. L, 



