12 ARKIV FÖR ZOOLOGI. BAND 6. N:0 7. 



The mandibles (Figs. 16 & 17, Pl. II) are comparati- 

 ve]y larger than those of O. quercus and of a deep green 

 colour, except at the edges which are brown. The shape is 

 the same as in the other two species, with double terminal 

 tooth; the upper tooth has at the inner (median) edge, near 

 the top, a narrow incision; the lower tooth is considerably 

 shorter than the upper one and curved in an even curve 

 towards the middle, with narrow pointed top. Of the two 

 usual hairs on the dorsal side, one is placed close to the 

 lateral side, the other near the middle. 



The maxillse (Fig. 2, Pl. II) are comparatively broader 

 than in O. quercus; the lobus is shorter, broader at the basa 

 and at the median edge provided with a comb of 7 straight 

 and pointed bristles, which are as long as the lobus. 



The labium (Fig. 2, Pl. II) is broad at the base and 

 tongue shaped, with convex sides and rounded anterior edge; the 

 latter, which is soft, as in the other species, has numerous 

 minute cuticular teeth arranged in transverse rows; the 

 palpi are small, not longer than they are wide at the base 

 and rounded at the top; they are placed so close to the 

 anterior edge that they project a little beyond it. 



The thorax (Fig. 12, Pl. 1). The thoracal segments are 

 shorter than the following segments of the abdomen, with 

 more flat ventral and less arched dorsal side; they diminish 

 in size sucessively forwards. 



The prothorax is slightly longer than the other two seg- 

 ments and is protected by shields both on the dorsal and 

 ventral side. 



The two dorsal shields are irregularly quadrangular, half as 

 long as the segment and separated in the middle by a 

 narrow streak of white cuticle. The ventral shields are three, 

 as in O. quercus-, their shape is seen in fig. 16, Pl. I. 



The cuticle of these shields is not provided with any 

 spinulse, but is quite smooth or even polished. 



The abdomen (Fig. 12, Pl. I); the 3—4 first segments 

 are of equal size, but the following ones diminish successively 

 in height and width; the 8—10 form a kind of tail, which 

 however tapers much more gradually than i O. quercus. 



The dorsal side of the 1 — 7 segments is highly arched 

 in the middle, so that on lateral view these segments appear 

 to have broad conical dorsal projections, which are about Vs 



