258 Variation in the Mealworm, Tenebrio molitor 



No. 23. It may occur, however, that even from the posterior 3rd 

 part of the elytra the edges diverge, so that a part of the abdomen is 

 visible (Fig. 12 6), or the divergence is only small and confined to the 

 distal part of the elytron. 



No. 24. Sometimes this phenomenon is accompanied with a reduc- 

 tion of the elytra. 



3**. As perforations. 



No. 25. The wings display holes of various shapes, number, situation 

 and extent, either on one wing-cover or on both (Fig. 12, c^ and e"). 



4°. As blister-like swellings. 



No. 26. They may occur on any part of either or both wing-covers, 

 in different shapes and extents (Fig. 12 (P; d* ; d% 



The variations mentioned under 3° and 4° are evidently the conse- 

 quences of developmental disturbances. The reduction and divergence 

 of the elytra are frequently normal specific characteristics in other groups 

 of beetles. 



h. The Legs ; the Tarsus. 



The group of the Heteromera, to which Tenebrio belongs, owes its 

 name to the unequal number of tarsal segments, which is five for the 

 1st and 2nd pair of legs, four for the 3rd pair. 



The number of tarsal segments in T. molitor may be increased or 

 decreased. This decrease may be observed (though not always simul- 

 taneously) in all three pairs of legs. It may go to the extent that the 

 tarsus finally consists of only one segment bearing the claws. 



Often there is not a trace of any indication that the reduction has 

 been brought about by a fusion of the segments. These are then of a 

 normal length and shape, as the under-mentioned figures show. 



No. 27. Fig. 13 6 I 



No. 28. „ c \ 1st leg. 



No. 29. „ e J 



No. 30. 

 No. 31. 

 No. 32. 



No. 33. 



No. 34. 

 No. 35. 

 No. 36. 



Fig. 15 c 

 d 



2nd leg. 



3rd leg. 



