TIIYSANURA. 



553 



at the ba.>e of the anterior wings. Both sexes of the 

 also produce similar though feebler chirping sound>, by 

 rubbing the femora of the posterior legs against the edge of the wing- 

 covers. 



Insects are almost universally distributed, from the equator to the 

 extreme limits of vegetation ; certainly with a considerable diminu- 

 tion in the number of species, and in their size and beauty of colour. 

 Some forms are truly cosmopolitan, e.<j., Vanessa runlvi. Fossil 

 nsects are found in 

 increasing numbers of 

 species, from the car- 

 boniferous formation to 

 the tertiary period. The 

 best preserved are those 

 enclosed in amber and 

 the impressions in the 

 lithographic slate. 



()r<l?i- 1. TIIYSANURA* 

 (including COLLEM- 

 BOLA). 



Win (/less insects, 

 Jiairi/ or sea/// 1><><l ;/ crer- 

 i HI/ : n-itli rudimentary 

 masticating mouth part* 

 mill setiform anal fila- 

 ments, /rhic/t mai/ w/vv 

 as a springing appara- 

 tus, at tin 1 cinl of the 



ten-segmented abdomen. 

 Development w itJi <> H t 

 mettimorpJiosis. 



The Thysanura seem to have preserved most completely the 

 primitive character of the oldest insect form*. The elongated 

 Cam poil i<la- particularly recall certain Myriapods, especially since 

 they may have rudimentary feet on the abdomen (tig. 459, a, !>). 

 On this account the Ca/npoiliila' have been regarded a> ancestral 



FIG. 459. rt, Citmpodea xtajihylinut (after J. Luliliock). 

 b, Anterior half of the body of C. Fnigili* (after 

 Palmen). Tr, Trachea; S, stigmata; P, legs; I", rudi- 

 mentary aluliuiiiual feet. 



* John Lubbock. " Monograph of the Collernbola and Thysanurn." 

 1873. 



