GENEBAL REMARKS. 97 



Heteropterous bugs are often noted for their 

 abominable odours, but the Tettigidae hitherto known 

 are innocent in this particular. It is yet to be tested if 

 any of these forms are distasteful to birds or other 

 enemies, and, if such be the case, whether they are 

 imitated by other species. Philcenus exclamationis might 

 easily be mistaken for Deltocejjhalus ; and, indeed, all 

 the larvas of the British Aphrophorae, in certain 

 respects, show outward resemblance to Deltocephali.* 



Dr. Puton names, in his list, no less than ninety- 

 four species of European DeltocephaU,—iiia,nj of these 

 on the authority of Dr. Fieber, whose type specimens 

 are, in a great measure, lost. Dr. Sahlberg and also 

 Mr. T. Edw^ards, for specific purposes, lay some 

 stress on the proportional lengths of the head, as 

 measured against the length of the pronotum. 



The difficulty of using such measurements is great, 

 particularly as dimensions may apparently differ if 

 seen perspectively on different planes. Moreover, the 

 head is in a small degree retractile below the fore 

 margin of the pronotum. Particulars of such mea- 

 surements need not, however, be disregarded, although 

 it is almost impracticable in such minute insects 

 to eliminate all errors of oblique vision under the 

 microscope. 



I have endeavoured to draw with some accuracy the 

 neuration of many of the foregoing species ; but in 

 several cases I have been obliged to obtain informa- 

 tion from dry carded specimens. Some of these 

 examples were at the time of mounting unique, or 

 they were specimens of rare species. This circum- 

 stance rendered their dismemberment for detail- 

 drawing undesirable. 



Even when the elytra have been raised from their 

 overlappings, the wings below are so intimately 

 folded and embraced by their own nervures, that 



* The canary bird will devour almost any number of the larvae of 

 Philcenus spmnarius, and as the spume itself does not appear to be dis- 

 tasteful to it, it does not act as a deterrent through any bad flavour. 



VOL. II. H 



