238 Variation in the Mealworm, Tenebrio molitor 



Males and females are represented here in nearly equal numbers, 

 viz. 1004 % to 1000 </. 



In the beginning of the month of April the first pupae appeared. 

 The males were at first in the majority, and that in such a manner 

 that 3 male individuals were obtained to 1 female. Gradually the 

 number of females increased, yet not so much but that in the end 

 of that month this ratio was still 125 j" — 100 %. In the month of 

 May the females appeared in a greater number, so that by the end of 

 May the ratio was the reverse of that in the end of April, namely 

 100 cT — 123 $ . Only in the month of June </ and % appeared in about 

 equal numbers, namely 100 J^ — 103 $. The result over the whole 

 gathering-period was as is mentioned above viz. 1000 (/ — 1004 %. 



This original predominance of the males did not, strange to say, 

 reappear in my own cultures, in subsequent years. In these as a 

 rule the appearance of males and females was generally numerically 

 equal in the various periods of the gathering. Perhaps the environ- 

 mental conditions, which were in my cultures, of course, much more 

 equable than in trade populations, play a part in this phenomenon. 



The ratio of the sexes was verified once more in a great number of 

 divers cultures of the generations 1918, 1919 and 1920. In all, 13,754 

 pupae were examined, which were represented by 6866 males and 6888 

 females, i.e. 1000^^—1003 $. 



3. The Difference in Length between the Sexes. 



Larvae and beetles are difficult to measure in a living condition. 

 Through fidgeting and uneasiness, and other causes, they give rise to very 

 unreliable figures in measuring. The pupae are very uneasy when 

 measured immediately after their emergence from the larvae. They turn 

 round, stretch themselves, contract or make all kinds of contortions ; in 

 short they try to resist the operation. 



Also the softness of their body renders it generally impossible to 

 determine their length exactly. If, however, the pupae are left to 

 themselves in the incubator for 48 hours, then all difficulties are at an 

 end. The body of the pupa has become a firm tractable object by the 

 hardening of the chitinous skin. Its movements are much less violent, 

 they quiet down sooner, so that we find no longer any difficulties. 



The mode by which the pupae, whose shape is as a rule strongly 

 crescentic, were measured will be explained more clearly in another 

 paper, and the results of the investigation as to length will be given in 

 connection with hereditary and environmental factors. 



