British Hymenoptera. 179 



14. Nomada bifida, Thorns. (PI. VIL, figs. 7— 7&). 



Thorns., Hym. Scand., ii., p. 196. 



This species is very closely allied to ruficornis, but the 

 bifid mandibles and the following characters will dis- 

 tinguish it easily. 



(J . Mandibles bifid at the apex, the pubescence of the thorax 

 denser, and the spines at the apex of the posterior tibiae hidden in 

 a dense tuft of very fine silvery hairs (for genitalia see PL VII., 

 figs. 7—7 6). 



J . Mandibles bifid ; metathorax with a conspicuous patch of 

 silvery hairs on each side below the basal triangle ; posterior tibiae 

 with the spines of equal length, and the apex clothed with a fine 

 close silvery white pubescence. 



In colour both sexes resemble ruficornis in almost every par- 

 ticular, i. e., certain of its varieties, as bifida does not vary to such 

 an extent as ruficornis ; in the ^ the pale bands of the abdomen 

 are generally continuous or nearly so, and the $ has generally two 

 very large lateral spots on the 2nd segment, a small one on each 

 side of the 3rd, and a transverse line across the middle of the 4th 

 and 5th at the base. Length, 8 — 11 mm. 



Hah. The only localities I know for this species at 

 present are Canterbury, May ; Chobham, June ; and 

 near Norwich, J. B. Bridgman ; but I have no doubt that 

 it is mixed in many collections, as it was in my own till 

 quite lately, with ruficornis. F. Smith evidently recog- 

 nised the characters of bifida, but apparently doubted if 

 they were of specific value, as I find, in some MS. notes 

 of his, kindly lent to me by Dr. Mason, the following 

 remarks under rvficornis : — ** The types in Kirby's col- 

 lection are all the dark-coloured vars. I am not satisfied 

 of the dark vars. being identical with the pale examples 

 which are described by Kirby under the najne flava ; the 

 differences which present themselves are a general darker 

 shade of red on the abdomen, and in the markings of 

 the head and thorax. The ocelli are usually enclosed in 

 a red ring. The wings are clouded with dark stains, and 

 the mandibles are shorter, stouter, and usually bidentate, 

 the teeth more or less developed ; in fiava the mandibles 

 are sensibly more slender, longer, and not bidentate, but 

 terminate in an acute point." 



