Bayford : Sire x juvencus and S. noctilio in Yorkshire. loi 



' Help Notes towards the determination of British Tenthre- 

 dinida}, etc.,' appearing at intervals in 'The Entomologists' 

 Monthly Magazine.' The following- remarks made me doubt 

 the correctness of the record above-named : — 



' Two species are pretty often found in this country, gigas L. 

 2i\\<X noctilio Y . { = ?neianocerns Thorns.) .... Specimens 

 of 7ioctiLio F. are, I believe, constantly recorded under the name 

 juvencus F., and I have probably named them so for corres- 

 pondents myself. But if the true juvencus occurs at all in 

 Britain it must be very rare. I have it from Switzerland, but 

 have never seen a British specimen which I can confidently refer 



to it (If any collector has a British specimen 



corresponding to true juvcficus .... I should be exceed- 

 ingly grateful for a sight of it).' 



Acting on this invitation, I sent for determination the various 

 species I thought I had, and included with them a specimen 

 in every way, but size, identical with my recorded juvencus, 

 recently taken at York. Dr. Corbett also sent the specimen 

 recorded by him as juvencus in ' The Naturalist' for November. 



This last proves to be a female of the true juvencus F. Mr. 

 Morice says, ' It is the first I have seen with a definite British 

 locality of origin.' The rest were males and females of gigas L. 

 and noctilio F. The three species are thus proved to occur in 

 Yorkshire. In this connection it may be as well to acknowledge 

 the prescience of Mr. W. D. Roebuck, whose suspicions as to 

 the correctness of determination of the Yorkshire specimens 

 recorded as juvencus F. deserve quotation. Writing of the 

 'Yorkshire Hymenoptera in 1878,' he said, 'These specimens 

 [from a colliery near Barnsley] (and also one which was taken 

 alive in Leeds in 1877 ....), although usually referred to 

 S. juvencus, seem to agree tolerably well with Thomson's 

 description of his melanocerus. But in view of the great 

 variability of the insects of this genus, it remains for further 

 investigation to show whether they really appertain to the new 

 species [i.e., melanocerus Thoms.] or are merely aberrant speci- 

 mens of the old one; or even to show whether S. melanocerus 

 itself be truly distinct from its congener' (Trans. Y. N. U. for 

 1880). 



Like all internal feeders, specimens of Sirex vary very much 

 in size, some being fully twice as large as others. They are 

 also liable to become greasy in time, but an occasional bath in 

 benzine or petrol will remedy this at least in part. 



1905 April I. 



