S. A. Arendsen Hein 



243 



they are covered completely dorsally by the elytra, ventrally by the 

 last abdominal segment. 



When the beetle is turned on its back and the abdomen is pressed 

 with a stiff pencil, then emerges in the </ the valve with its deep 

 incision, in the $ the ovipositor (partially still telescoped) so that 

 the sex can be determined immediately, by this feature, as well as by 

 the two palpi at the distal end of the ovipositor. 



The deep incision in the valve in the ^ serves apparently to give 

 passage to the penis, lying dorsal to it, when this organ during the 

 copulation bends ventrally and in a forward direction ^ 



'0'<iA\k/La)C 



5 



Fig. 10. 



In connection with this we can understand why the membranes 

 between the 3rd and 4th and between the 4th and 5th segments are 

 more conspicuous in the ^ than in the $, as has been mentioned 

 above. For these ample membranes render a hinge-like movement 

 possible in the segments concerned, a movement which occurs when in 

 the cT those segments are bent ventrally during the coition. 



Of the above-mentioned characters this last is infallible. 



In the thousands of beetles which have been examined as to the hairs 

 of the tibia, there occurred not seldom cases (as has already been 

 mentioned) where in the ^ a row of erect hairs was wanting, whereas 

 this absence is normal in the % without exception up to the present. 



But the sex-differences mentioned above, will give almost absolute 

 certainty. 



2. Duration and Quantity of the Egg-ProductioTU 

 The eggs are deposited not in batches, but one by one, isolated. 

 They have a milk-white colour, are oblong-oval in shape, 1-75 mm.' 



1 After this paper had been sent to the editors of the Journal of Genetics, I became 

 acquainted with the study of Kerschner dealing with the male copulation organ of T. molitor 

 published in Zoologische JahrbiicUer, Bd. xxxvi. in which the author has given a sketch 

 of the valve mentioned above, and of the male and female pupae. 



Journ. of Gen. x 17 



