138 



B. P. UVAROV, 



A study of long series of both forms showed that the differences in the vertex, 

 as given above, are quite unrehable, since the median keel of the fastigium proved 

 to be absent in one per cent, of the specimens of migratoria, as well as in about 7 per 

 cent, of danica ; the transverse keel was found in 80 per cent, of migratoria and in 

 about 47 per cent, of danica ; as for the flatness or convexity of the vertex, it is 

 too indefinite a character to be reliable. The only trustworthy characters are, 

 therefore, the shape of the pronotum and the relative length of the elytra and hind 

 femora. In order to avoid, as far as possible, any subjective judgment, I have 

 expressed these characters in terms of actual measurements. This is quite simple 

 in the case of the elytra and femora, since there exists an inverse proportion between 

 their lengtlis, and we may simply express the length of the femora as a percentage 



cA 



^ )>. :.. 



Fig. 1. Lociista migratoria, L. : A, B, phase danica, L., (^, Turkestan; C, D, ph. migratoria (^, 

 progeny of preceding specimen ; E, ph. migratoria, typical $, Astrakhan ; F, elytron. 

 Elytron natural size, remainder X 3. 



of the length of the elytra. As for the shape of the pronotum, numerous measure- 

 ments have shown that the width of the metazona (measured between the shoulders, 

 i.e., at its widest), if expressed as a percentage of the length of the w^hole pronotum 

 (along the median keel), gives the best and most reliable impression of the actual 

 shape. The relative height and form of the median keel, which seem to be excluded 

 from consideration by using this proportion, is but a secondary character which 

 depends entirely on the relative length and width of the pronotum. If we imagine 

 that the short and broad pronotum of migratoria undergoes a lateral compression, 

 we may expect it to become longer, and its median keel higher and convex, especially 

 in the metazona, which should be most influenced by lateral compression ; there is 

 no doubt, therefore, that the shape of the median keel must be, and actually is, subject 

 to changes correlated with those of the length and width of the whole pronotum. 



