1S.1T.] 175 



A^ NOTE ON T HE BIOLOGY OF STEXUS SIMILIS Herbst. 



BT K. G. BLAIB, B.Sc, F.E.S. 

 (Published by permissiou of the Trustees of the British Museum.) 



A single full-grown larva of this species was captured at Callington, 

 Cornwall, on June 22nd, on the underside of a leaf of Burdock (Arctium 

 lappa), and two cocoons of the same species, each containing a pupa, 

 were found on other leaves of the same plant. 



As S. hipunctatus Er. appears to be the only member of this genus 

 whose larva has been described (Schiodte, Nat. Tidsskr. 1872, iii, 8, 

 pp. 548-552, t. 18. figs. 1-9 * ; Fowler, Col. Brit. Isl. ii. p. 328), and 

 nothing is recorded of its mode of life or pupal state, these incomplete 

 notes on the life-history of S. similis may be of intei'est. 



The larva is very similar to that figured by Schiodte, with very long 

 and slender antennae, palpi, and legs, but shows various minor points 

 of difference. The anterior clypeal margin instead of being rounded 

 with six small teeth is truncate in front with three small teeth, one 

 median and another at each angle of the truncate margin. The ocelli, 

 six in number on each side, form an open ring with a gap behind large 

 enough to contain an additional one; in S. h/puiictati/s the ring is 

 complete. The long basal joint of the anal cerci is rather strongly 

 expanded in the middle. 



The cocoon is a double structm-e, spun flat against the under side 

 of the leaf; it is white, and very' similar to that of Gomventzia (Coin'o- 

 pierijx) psociformis, though larger and of not so close a texture. The 

 inner cocoon is regularly elliptical, measuring 7\ x 4| mm. ; the outer 

 one, more irregular in its outline, measures about 16 X 11 mm. 



"When first found it was possible to distinguish vaguely the pale 

 whitish piipa within its double envelope, but when examined on my retura 

 home, on July 4th, the beetles had emerged from both, and one was 

 already dead. It is a matter for regret that the pupa was not more 

 closely obser\'ed. 



The situation in which they were found was in an orchard on some 

 steeply rising grovtnd about 100 feet above and 150 yards distant from a 

 small stream. Though diligent search was made, no further specimens 

 were found on neighbouring plants. The larvae had probal)ly been 

 feeding on some Aphids inhabiting the same leaves. 



British Museum (Xat. Hist.), 



Cromwell Road, S.W. 

 Juhj 16th, 1917, 



* Reproduced by Ganglbauer, Kiif. Mitteleur. ii. 1S95, pp. 547, 551, IF. 25,26: Eeitter, Fauna 

 Germanica, ii. 190il, t. 52. f. 1, 



