I. TRÄGÅRDH, METAMORPHOSIS AND BIOLOGY OF ORCHESTES. 11 



Metamorpliosis. 



1. The lar va. 



The fullgrown larva attains a length of nearly 6 mm. 



The c o lo ur is quite white; on]}^ tho head-capsule and 

 parts of the prothorax are brown-coloured. 



The cuticle (Fig. 11, Pl. I) is minutely spinulated; the 

 base of the spinulse is somewhat swoUen, their tips point 

 backwards. Unlike those of the larva of O. quercus the spinulae 

 are quite colourless. 



The head capsule is dark chestnut-brown coloured; 

 its posterior margin is deeply excavated and the posterior 

 angles project strongly and are hidden underneath a fold of 

 the prothorax. 



The fr ens is very large and triangulär, as in O.populi. 



The clypeus (Fig. 1, Pl. II); the sides are straightand 

 converge forwards, the anterior margin has a deeper but 

 narrower incision than in O. quercus; one pair of thickenings 

 far laterally and near the anterior margin; they are more 

 pointed than in O. quercus; 2 pairs of small hairs laterally, 

 behind the middle. 



The labrum (Figs. 1 & 2, Pl. II) has a slightly convex 

 anterior edge, which projects a little in the middle ; the sides 

 are straight and converge forwards; the posterior margin has 

 a median triangulär projection, rounded at the top. 



Two pairs of bristles on the dorsal side; one pair inserted 

 near the middle a little in front of the postero-lateral angles, 

 is very short and blunt, whereas the other pair, which is 

 placed near the anterior edge far laterally, is more jTointed. 



At the anterior margin we notice 7 pairs of bristles; of 

 these the 3 lateral pairs are more than three times as long 

 as the others and more straight and pointed; the other 4 

 eurve downwards and backwards near the base. 



On the ventral side (Fig. 3, Pl. II) of the labrum we 

 notice two short, but rather high, oblique and bar-shaped ridges, 

 on which two pairs of very stout blunt and conical bristles 

 are inserted, which point obliquely forwards and downwards. 



The antenn 86 are nearly of the same shape as in O. 

 populi, with one oval, concentrically striated appendage and 

 3 — 4 small sensorial, conical processi. 



