Early stages of Latiorina pyrenaica. 401 



that has most on it is being destroyed in a way that shows 

 they are still active. 



Oct. 12th. — The plant referred to in last note is much 

 destroyed, but a visit at midnight did not result in any 

 larvae being seen. The heads or crowns of the plant have 

 their centres eaten out, and these seem to die off, the leaves 

 that remain becoming dead and brown. The larvae must, 

 of course, be hiding somewhere amongst the old leaves and 

 stems beneath the living (or now dead) surface of the plant. 

 The first-stage larva has hairs, lenticles, etc., as shown 

 in PI. LXX and LXXI. On comparing these with the 

 same stage of L. orbitulus (Trans. Ent. Soc. Lond. 1911, 

 PI. XIII), there is seen to be a difference much greater than 

 might have been anticipated from the close relationship of 

 the two species. At first glance, the much greater size and 

 boldness of the hairs and hair bases in L. orbitulus is strik- 

 ing. On coming to details w^e find this is very marked in 

 the first dorsal hairs on each segment, the base of which 

 is very large in orbitulus, small and delicate in pyrenaica; 

 even more important, the second hair, which almost rivals 

 the first, is actually wanting in pyrenaica. Curiously, the 

 small accessory hair at the front margin of the segment is 

 much the same in both species. The third hair (supra- 

 spiracular) compares in the two species much as the first, 

 bold and strong in orbitulus, delicate in pyrenaica. The three 

 marginal (sub-spiracular) hairs are, like the others, weak 

 in pyrenaica, but they differ also in position ; in orbitulus the 

 middle one, as in most of these larvae, is ventral to the other ♦ 

 two, but otherwise in an intermediate position ; in pyrenaica 

 it is almost directly ventral to the posterior hair. So far 

 these details refer rather to the abdomen. On the thorax, 

 the metathorax is, in pyrenaica, similar to the abdominal 

 segments ; in orbitulus it differs from them in possessing a 

 hair in front of I and II that emulates them in size, and 

 may or may not represent the very minute front hair of the 

 abdominal segments. On the mesothorax the hairs have 

 the same arrangement in both species, except that pyrenaica 

 has only three (sometimes two only) instead of four mar- 

 ginal hairs. The hairs on the prothorax are the same in 

 both, but look very different owing to their slenderness and 

 minute bases in pyrenaica, and this is enforced by the absence 

 of the pair of lenticles on the prothoracic plate, present in 

 nearly all first-stage Plebeiid larva. This absence of lenticles 

 affects other segments also. The dorsal lenticle is absent 



TRANS. ENT. SOC. LOND. 1915. — PARTS III, IV. (jUNE) D D 



