1881.] 53 



(9) 6. Nerves not darker than elytra. 



(8) 7. Face with five black spots impurus. 



(7) 8. Face with four black spots distinctus. 



(6) 9. Nerves darker than the elytra. 



(11) 10. Nerves but little darker than the elytra. Face with very in- 



distinct traces of the short, double, longitudinal, dark 



line between the two uppermost spots ... fuscinervis. 



(10) 11. Nerves black or nearly so. 



(13) 12. Nerves of the coriuni only black. Face without any trace of 



dark markings between the two uppermost spots nassatus. 



(12) 13. Nerves of corium and membrane black, or nearly so. Face 



with a distinct double, longitudinal dark line between 



the two uppermost spots scutellatus. 



(5) 14. Face not distinctly spotted with black. 



15. Elytra brownish - testaceous, sprinkled with fuscous atoms. 



Head and thorax greenish-yellow tih'a. 



16. Elytra testaceous, with an abbreviated, transverse, dark brown 



band in the middle cereus. 



17. Elytra testaceous, nerves darker, along the costa a narrow 



dark line ulmi. 



The above tables (which, with one or two exceptions, were drawn 

 with the insects before me) may perhaps be useful in naming any of 

 the species hitherto recorded as occurring in this country ; but they 

 are only intended as a key to the detailed descriptions which have, 

 from time to time, appeared in this Magazine, and, like all contrivances 

 of their kind, they mast be applied strictly and with great care. 



Agallia jmncticeps and venosa are common, but hrachjptera is, I 

 believe, only recorded from Scarborough. Macropsis microcephala is 

 said to be attached to Helianthemum, and is therefore local, but 11. 

 lanio is common everywhere on oaks. 



The determination of the species of Idiocerus presents no diffi- 

 culty, except, perhaps, in the case of populi and fulgidus. The latter, 

 however, may be separated by the structural characters given above. 

 The difference between the very narrow and gradual antennal plate of 

 $ fulgidus and the oval abrupt one of populi, although not noticed in 

 Kirschbaum's description, is very striking. I. venustus I omit on the 

 authority of Mr. Scott, who says that it " may be considered as a 

 variety of I. varius." The number of our species, however, remains 

 the same, as I am able to introduce with certainty the genuine I. varius, 

 Fab. My experience of the habitats of these beautiful insects is as 

 follows : adustus and lituratus common, on willow trees ; varius scarce, 

 on osiers ; Heydeni and H-alhwn on Lombardy poplars ; confusus on 

 white poplar ; fulgidus on black poplar ; and populi on poplars 

 generally. 



