242 Variation in the Mealworm, Tenebrio molitor 



difference, namely the character of the connective tissue between the 

 4th and 5th segment, is in many cases still more striking. 



In the </ as well as in the $ the separation between the 1st and 

 2nd, and also between the 2nd and 3rd segments, shows only one line, 

 being the distal edge of the most anterior segment, which after the 

 fashion of a tile covers the front edge of the following segment. The 

 separation- lines between the 3rd and 4th and between the 4th and 

 5th segments are in the (/*, as well as in the % , no longer a single line, 

 but a double one. Both lines form together the arc of a circle with the 

 chord of that arc ; the arc is the distal edge of the preceding, the 

 chord the proximal edge of the following segment. The space between 

 chord and arc (which in the (/ is strikingly larger because the distal 

 edge of the 4th segment is much more strongly concave) is spanned by a 

 light coloured membrane (connective skin between the two segments) 



Fig. 9. 



which as a rule contrasts strongly with the dark coloured surroundings, 

 and is consequently, by its larger surface, immediately observed in 

 thee/. 



By the greater concavity of the distal edge of the 4th segment in 

 the (/, this segment has, in longitudinal direction, become narrower 

 than in the $ , where this narrowing is very slight or absent. 



c. Shape of the Ventral Valve, which covers the Exterior Sexual 

 Organs. 



Penis and ovipositor are covered dorsally and ventrally by a crescent 

 shaped plate, or valve (Fig. 10). In the (^ the ventral valve is in the 

 median-line divided into two lobes by a deep incision. In the $ this 

 incision is wanting, and the distal edge of this ventral valve forms an 

 uninterrupted curved line. Both valves (the dorsal and the ventral) 

 are invisible in beetles that have attained their adult colorations, as 



