632 New Species of S) rex. 



excepting the two, or sometimes three, basal segments, which 

 are cyaneous, and there is a very conspicuous violet reflexion 

 upon the ferrugineous portion ; the posterior tibiae and tarsi are 

 of a deep dark blue ; as are also the intermediate pair, either 

 entirely, excepting only the joints, or merely externally; the 

 wings are ferrugineous, with their nervures and stigma deeply 

 so. It occasionally, but rarely, varies in having the basal 

 joints of the antennae, or the posterior tarsi, ferrugineous. 



This species inhabits the spruce fir (Pinus nigra) ; and the 

 time of its developement is the latter end of May, and the 

 beginning of June, after which it is not found ; and they last 

 about a fortnight. This is the observation of the person who 

 captured the present species in Cambridgeshire this year. 

 Twenty-seven males and sixteen females I have had the 

 opportunity of inspecting, and which, excepting the difference 

 of size, and the slight ones arising, probably, from immaturity, 

 noticed at the end of the description of the male, are all 

 exactly alike. A comparison of this insect with the Sirex 

 juvencus offers very marked distinctions : in the first place, 

 in its habits, as above noticed ; for the same person captured 

 the juvencus in a neighbouring plantation of Scotch fir 

 (Pinus sylvestris), and only there ; and the time of its deve- 

 lopement is towards the end of July, and never earlier. This 

 fully concurs with all the German accounts of it; but, should 

 these differences not be admitted, those resulting from a compa- 

 rison of structure and colour will settle the question. In 

 Sirex duplex $ , the terminal segment of the abdomen is consi- 

 derably more acuminate than in the juvencus; and the pos- 

 terior tibiae and tarsi are larger ; and, in the female S. duplex 

 the aculeus is the great distinction, which is considerably 

 longer, and the corniculus more acuminate; but the wings, 

 also, in both sexes of the latter species are much darker. It 

 is exceedingly interesting to find two insects so very closely 

 resembling; and it would suggest many hypotheses, had I time, 

 at the present moment, to indulge in them ; yet I cannot sup- 

 press one question, which it is for the botanist to determine; 

 and this is, How far does this tend to connect the Plnus syl- 

 vestris and Pinus nigra more closely and intimately together ? 



This notice being upon the genus Sirex, I may observe that 

 Fabricius's Sirex albicornis, which he, in his Systema Pieza- 

 tomm, fancies may be an Oryssus, is certainly a true Sirex ; 

 for I have it : and that it is so, the description of the aculeus 

 and corniculus evidently proves. He, probably, may not have 

 seen the insect, after he first described it in 1781 : yet it is no 

 excuse for not knowing its genus. 



Chelsea, Nov. 26. 1837. 



