18 ARKIV FÖR ZOOLOGI. BAND 6. N:0 7. 



On the 1st to the 8th segments we notice stigmata, which 

 are dark coloured and very conspicuous. The ventral side 

 of the abdomen is almost flat, the dorsal side of the 1st to 

 the 7th segments is highly arched so that on lateral view the 

 segments appear to ha ve large conical projections half as 

 high as they are wide at the base. On the top of the pro- 

 jections there are narrow oval transverse areas, where the 

 cuticle is thin and has no cuticular teeth. In the middle of 

 the areas there seems to be a fine cuticular fold. The pro- 

 bable function of this will be discussed låter. 



The 3th to the lOth segments taper as above stated gradu- 

 ally towards the top and diminish at the same time in length, 

 so that the 9th segment is scarcely half as long as the Sth, 

 and the lOth not half as long as the 9th. 



The lOth one, the pygidium, is very short, not longer 

 than it is wide at the base, and perfectly conical. 



On the formation of the cocoon of O. fagi and O. quercus. 



That the larvse of these beetles spin a cocoon when going 

 to pupate is a well-known fact. But how this cocoon is 

 formed is, curiously enough, not yet known. 



Ratzeburg [8 p. 154] merely says »die Larve (von O. 

 fagi) hat Spinn werkreuge» and Pissot, who gives a detailed 

 account of the habits of the larva of the same beetle says 

 [7. p. 92] »Gette larve filé a la maniére des chenilles; si on 

 la tire de sa mine, elle demeure suspendue a un fil de soie». 



It seems incredible that Pissot, who noticed that the 

 larva häng suspended on a thread of.silk, did not take the 

 trouble to assert that the thread emerged from the anal 

 aperture, not from any spinneret! 



If we keep some fullgrown larvse in their leaves in confi- 

 nement and open a blotch, when the larva is observed to start 

 spinning the cocoon, which is easy to discern through the thin 

 epidermis of the leaf, it is, however, very easy to ascertain 

 that a fine liquid thread emerges from the anal opening. 



As through Silvestri's researches [11. p. 67 — 84] we 

 know, that in the larva of Lebia scajmlaris, which also forms 



