1911.] 5 



29 (28) Elytral interstices of female without punctulation. Left side-lobe 



of ffidoag-us with a large triangular tooth near the middle of its 

 concave edge. iEJdeagus narrowly pointed, its convex edge a little 

 subangularly dilated near the middle immaculatus, Gerh. 



30 (17) Head black or blackish. Thoracic impression falcate reaching at least 



to the lialf-length of the thorax. Metasternum with two straight, 

 divergent keels lineatocollis, Marsh. 



I have been influenced iii luy decision to regard all the above as 

 separate species by the following- considerations. Wliilst it may 

 reasonably be doubted whether any universally acceptable definition 

 of the term species exists, it is certain that in practice the majority of 

 naturalists at the present day use this term in the Linnaean sense, 

 a conception essentially based on the idea of common descent or 

 family relationship. Under these circumstances it appears desirable 

 to use the term variety, which at present cannot be said to have any 

 definite signification, also in the Linnseau sense, i.e., as relating to 

 something within the species. To take a concrete example : — 

 H. heydeni is usually put as a variety of ruficollis ; but, having 

 regard to the characters which heydeni exhibits, is it consistent with 

 human experience to suppose that amongst the offspring of ruficollis 

 parents some will be rufieoUis and some heydeni f If it is not, then 

 heydeni comes within the Linnsean idea of a species and should be 

 treated accordingly. Halipli do not acqviire their full colouring for 

 some time after they have reached the imago state, and this circum- 

 stance, which is particularly noticeable in autumn-caught specimens, is 

 apt to lead to errors of determination if coloiu- and pattern be unduly 

 relied on. 



ff. ohliquus, Fabr. — I have taken this species not uncommonly in 

 the Norwich district ; in the Cotswold district it is very common. The 

 black markings on the elytra vary considerably by way of exaggeration 

 and reduction. 



H. yaUens, Fowler {H. confinis var. fallens, Fowler, Col. Brit. 

 Isl., i, 153). — This species has the ground-colour of the same pale 

 yellow as ohliqtms, from which it differs in the possession of a longi- 

 tudinal impression, bounded outwardly by a distinct ridge, on the base 

 of the thorax opposite the fourth row of elytral punctures. The black 

 markings on the elytra somewhat resemble those of ohliqmis at first 

 sight, but the four inner lines are not widely interrupted liehind the 

 middle as in ohliquus ; the suture and base of elytra are narrowly 



