1832.] 205 



at the base ; it is marked by the usual angular stripe (as in H. scalaris) ; the legs 

 are often piceous ; the middle femora are ciliated beneath -with long hairs, the mid- 

 dle tibia? are thickened along their lower halves, and ciliated nearly the whole length 

 of their inner sides, the hairs becoming longer towards the apices ; the posterior 

 tibia? have a few long hairs of irregular lengths on their outer sides, and only the 

 usual short adpressed ones on their inner surfaces ; the poisers and scales are some- 

 times fuscous. Not very common. 



H. floricola, Meig. 



This species may be readily known by its brownish wings, and widish, straight, 

 interrupted dorsal band on the abdomen, having no angular dilatations. The tibia?, 

 especially the posterior ones, are piceous or sub-rufous ; and there are six strong 

 projecting spines on the infra-thoracic surface, one arising from the base of each 

 coxa. Not uncommon. 



H. carbonaria, Bond. 

 This little black species is well marked, and generally distributed ; the calyptra 

 are small, and, with the halteres, black ; the wings are fuscous ; the abdomen is 

 short and wide, flattened, and marked with the usual angulated dorsal stripe ; the 

 middle tibia? are thickened towards their ends, which are shortly ciliated on the 

 inner sides ; the posterior tibia? are unarmed ; there is a minute black spur or tooth- 

 like process on the under-side of each middle metatarsus at its base ; a similar but 

 larger process is found in the same situation in H. armata ; on close inspection with 

 •a good lens, this is apparently formed by a pencil of rigid black hairs. I believe 

 this species to be identical with the A. cerea of Meigen, but not with that of Zetter- 

 stedt ; the latter is considered by Loew to be the same as the A. gibbera of Meigen, 

 and to belong to the genus Azelia. 



(To be continued). 



MEASUREMENTS IN DESCEIPTIYE ENTOMOLOGY ; A SUGGESTION. 



BY R. McLACHLAN, F.R.S., &c. 



The following remarks now almost exclusively concern British 

 entomologists. Very few years ago they might have been applied far 

 more universally. The substance of them amounts to a suggestion 

 that millimetres, and not inches and lines, nor inches and fractions, 

 should be used in all descriptions ; in effect the decimal system should 

 be accepted. 



At the present moment, there may be considered to be no existing 

 "custom" amongst British entomologists, but many of them have 

 anticipated my suggestion by rendering it inapplicable to themselves. 

 In the volume of "Transactions" of the Entomological Society of 

 London for 1881, I find ,£ descriptive " papers from the pens of 

 sixteen authors, ten of whom use " inches " or " lines " (or fractions), 

 while six use "millimetres." And more than the "thin end of the 



