INVERTEBRATE ANIMALS. 89 



spit-insects, Cercopid(E ; Plant-lice, Aj^hid/e ; 

 Scale-insects, Coccidce; Cochineal-insects, Coc- 

 cus cacti; Shell-lac-insects, Coccus lacca. 



Observe the curious modifications of the " Lan- 

 tern " ; the waxen plumes in Lystra ; the 

 extravagant development of the prothorax in 

 some of the exotic Cercopidce. 



Small series of British species, presented by F. W. 

 Douglas. 



Group 200.— Family CICADID^E. >c»?cjc«/3r], the Screech-owl, 

 in allusion to its shrill note. Illustrated by about 36 

 species, including representatives of Polyneura, Gc^ana. 

 Observe the instrument by which the male Cicada 

 emits its loud note ; it is a tense membrane on its 

 sides near the base of its wings, and is well seen in 

 C. saccata, from Australia. 



A single species is found in Britain, where it is by 

 no means common. 



Upper Compartment. 

 Dmiduhia imperatoria, the largest species in the group. 



Group 201. — Order DIPTERA. Sic, twice ; 7tT=pov, a wing. 

 Wings two ; the lower pair of wings are replaced by a 

 pair of slender filaments clubbed at the tip, called 

 halteres or poisers. No two-winged fly has a sting. 



Estimated number of species, 24,000 (Bentham) ; 

 5,220 species are described in " Histoirc Naturelle des 

 Insectes Diptercs,'' J. Macquart, 11 vols., 1835-1855. 

 The British species exceed 2,000 ; " Insecta Britannica, 

 Diptera," F. Walker, 3 vols., 1856. 



1l Examples : Meat-flies, Muscidce : Gnats and 

 Mosquitoes, Culicidce ; Long-legs, Tlpididce ; 



