MORPHOLOGICAL EFFECTS OF CROWDING 



323 



differences in morphology, color, and ecological relations, he con- 

 cluded that these are distinct species, as many others have regarded 

 them. In hunting for dehmiting structural characters, two were 



P/fOA/or/iL Proport/oa/ 



Fig. ^t^. — Graph of the range in variation in the pronotal proportion in 358 speci- 

 mens of Locusla migratoria L. (After Uvarov 1928, by permission of the Imperial Bu- 

 reau of Entomology.) 



found — the proportions and shape of the pronotum and the relation 

 between the length of the elytra and the hind femora. The pro- 

 notum differences of these two forms are shown in Figure 32. The 

 differences may be summarized by saying that in L. migratoria (3, 4) 

 the pronotum is relatively shorter and broader than in L. danica 

 (1,2) and has a low median keel. There is a more definite constric- 

 tion in the middle of the pronotum, and the keel is straighter in pro- 



