1906.] 79 



HELP-NOTES TOWARDS THE DETERMINATION OF BRITISH 

 TENTHREDINIDM, &c. (12). 



BY THE REV. F. D. MORICE, M.A., E.E.S. 



{Concluded from page 33). 



TABLE FOR BRITISH CECESUS SPECIES. 



1. Mesopleurae shining (generally smaller than the other spp.) varus, Vill. 



— Mesopleurae dull, somewhat rugosely punctured 2. 



2. Vertical area more swollen and squarer in both sexes (1^ times broader than 



long). Hind tibiae and metatarsi (noticeably in the $ ? , and just appreciably 

 in the S S) dilated more suddenly, and to a greater extent, reaching their 

 maximum dilatation sooner, and rounded away again more gradually towards 

 the apex, than in the other species. (See fig. 10a) septentrionalift, L. 



— Vertical area flatter, and quite twice as broad as long in both sexes. The dilata- 



tion of the hind tibiae and metatarsi (especially in the $ ? ) more gradual, 

 their maximum dilatation quite near the apex, where it abruptly ceases. 

 (See fig. 10^.) latipes,Yi\\. 



Measuring the metatarsi of sepfentrionalis and latipes ? $ under 

 the microscope, I find that in septentrionalis they are a little more 

 than twice, and in latipes a little less than three times, as long as 

 broad. (The exact figures are ff, against f§). Their outline in the 

 former is roughly semioval, in the latter more clavate (subtrian- 

 gular). The colour-characters usually employed in distinguishing the 

 Croesus-^^ec\e% arc of little value. Generally varus $ has quite red 

 femora, septentrionalis. ? quite black ones, and latipes 2 black ones, 

 with a large red mark within. But septentrionalis ? also goes red 

 at times, and the (^ c? of all the species have the femora largely, if 

 not entirely, red. (The original description of varus professes to be 

 that of a (;^ ; but, strange to say, no example of that sex has ever 

 since occurred, and the type specimen seems to have disappeared !). 

 The wings of varus are clear ; but in both the other species they are 

 clouded, more or less in different specimens. Cameron says, that 

 latipes, J , has the antennae " faintly brownish beneath at the point," 

 but my own specimens do not bear this out. There is generally more 

 black at the apex of the abdomen in latipes (^ , than in septentrionalis 

 $ , but its extent varies in both. 



Miss Chawner, who has repeatedly reared all three species from 

 larvae found at or near Lyndhurst, has kindly given me full accounts 

 of the habits and appearance of tliese larvae, which agree with those 

 to be found in Cameron's Monograph. Varus is always found on 

 alder, the black larva of latipes always on birch, the bluish -green and 

 yellow larva of septentrionalis occurs on many different trees. 



