208 tHE BNtOMOLOGIST*S RECOKb. 



retlection will show the reasonableness of this. There is no test of 

 how much or how little of a description is necessary. Most generic 

 diagnoses are insufficient, many incorrect. Each generic title must 

 have its type, a type which shows the points of structure the generic 

 title covers or indicates. Genera without types are of no value to the 

 student, he cannot refer to any structure to verify the diagnosis. 

 Large genera without a type are in a metaphysical condition. They 

 are supposed to rest on " average characters," but no one species has 

 precisely these " average characters." Each species, as represented by 

 individuals of either sex, oft'ers characters specific, generic, and also 

 such as indicate its position in a certain sub-family, family, or super- 

 family. The one principle recognised in nomenclature is priority of 

 publication, and all rules are concerned to show how, under the 

 different circumstances attending the existence of names, this prin- 

 ciple is to be applied. The name belongs to literature, and is subject 

 to literary regulations. — (Prof.) A. Eadcliffe Gkote, M.A. 



The habits of Porthetria dispar. — During a recent entomologi- 

 cal trip to the Dauphine Alps, I made some (to me) interesting obser- 

 vations on the habits of P. dispar. To break my journey I made a 

 two days' (July 25th and 2Gth) stay at Aix-les-Bains, and visited the 

 woods on the hills between Gresy-Kur-Aix and the Lac du Bourget, a 

 locality previously described in this magazine (vol. vi., pp. 169-172). 

 One of the first insects that attracted my attention was F. dispar, the 

 males of which were flying rapidly about, in the broiling sunshine, in 

 much the same way as do those of Onjuia antiqua in Britain. They 

 were in thousands, both in the lanes and in the woods, but 1 observed 

 no females, the lack of large trees enabling them to hide successfully. 

 On August 18th I was at Bourg d'Aru (about 3,500 ft. elevation), in 

 the lovely Val de Veneon. Near the village I again saw the males in 

 large numbers, flying in the sunshine, and settling the moment it be- 

 came cloudy. These haunted the faces of the massive rocks that rise 

 from the path, and I was not long in detecting the females, seated 

 upon the bare rock, from which they fell helplessly when disturbed 

 with a stick. Here, too, some males were resting, sitting much in 

 the same manner as those of O. antiqua sometimes do, upon a window 

 or wall. This race, both males and females, was small, although 

 there was some variation in size ; but on the whole the specimens bore 

 much the same appearance as do those with which we are familiar in 

 Britain as the result of persistent in-breeding. There appeared to be little 

 doubt that the females had emerged from pup* whose cocoons were 

 hidden in the crevices of the rock, and that the males haunted the rocks 

 because the females were there. The days of August 20th and 21st 

 were spent at Grenoble. Both days were continuously wet and dull, 

 and entomological observations were at a discount. Strolling, how- 

 ever, under an avenue of plane trees, by the banks of the Isere, I was 

 soon aware that the trunks were plentifully sprinkled with the females 

 of /'. dispar. My curiosity awakened, I discovered that all the trees 

 forming the avenues in the town itself, as well as those in the public 

 gardens, were similarly tenanted. They were not difficult to detect, 

 yet they were certainly not conspicuous to the uninitiated. The moths 

 exhibited no very marked preference for any particular kind of tree on 

 which to rest, except perhaps in the case of the plane tree (the most com- 

 mon, by the way), all other kinds having tenants. They congregated 



