36 ILLINOIS BIOLOGICAL MONOGRAPHS [430 



of certain markings. Compare for example the anterior cross-band 

 (humeral lumile) of 436 and 427; one is turned forward with a char- 

 acteristic curve, the other backward. This is a difference between the 

 two species which holds good throughout all the individuals. The 

 extension of the white shown is clearly associated with a degeneration 

 of some of the chief tracheal trunks. 



From this large series of figures we must not permit ourselves to 

 judge that all types of pattern are equally common and equally general 

 in the species of the genus. Figures 329 to 333, and figures 130 and 131 

 show the commonest and most characteristic types in the genus which 

 are universally distributed and make up vast majority of the grand 

 total for the world. 



This, the first definitely directed tendency in the group, has been 

 the union of spots to form the characteristic markings of the group 

 shown in figure 49, plate V, as combination of Al, A2, B2, or B3 to 

 make the humeral lunule so called, of A4, B4, and B5 to make the so- 

 called middle band, and of A6 and7 to make the apical lunule of the 

 taxonomists of the group. If these three types of joining are granted 

 as the first directive principle entering into the make up of the patterns 

 of the group it must also be noted that it does not apply to the 

 majority of species in nine of Horn's groups (XXVII-XXXVI) includ- 

 ing 40 species (Figs. 188 to 215 and 220 to 231, PI. XIII) . A few patterns 

 with middle band and apical and humeral lunules, and which have 

 three spots in the basal and anal portion of the elytron, are included in 

 these groups and differ from most others of similar components in the 

 presence of these spots (Figs. 273 and 274, PL XIV, and 163 and 164, 

 PL XII). These few are the only representatives which show this char- 

 acteristic middle band humeral andj apical lunule. It applies to only 

 16 species of the Horn's pilosity groups XVIII to XXII which include 

 66 species in Africa (Figs. 147 to 149a, PL XII; 269, PL XIV; 156, 

 PL XII; 265, 241 to 272, 278 to 280, PL XIV). Of the figures cited, 

 156 and 265 are of the most primitive type and 266, 267, 275 and 278 

 show modifications. 



If we grant the majority of the remaining 500 species show these 

 characteristics as variations or that they may for purposes of discus- 

 sions be assumed to have been derived from forms which did have the 

 three characteristic markings we note that in general the patterns 

 except those mentioned above fall into two parallel series one without 

 the spots, including the majority of species, and the other with them, 

 including a' comparatively small number of species. Those with the 

 three spots are confined chiefly to the land directly bordering the Indian 

 Ocean being especially numerous in Africa and India. Spots may be 

 wanting in some variants of such species as escheri (Figs. 267 and 268) 



