INVERTEBRATE ANIMALS. 87 



Group 201. — Order DIPTERA. Si?, twice; Ttrepov, awing. 

 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) ; 

 5220 species are described in " Histoire Naturelle des 

 Insectes Dipteres," J. Macquart, 11 vols., 1835-1855. 

 The British species exceed 2000 ; Insecta Britannica, 

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



IT Examples : Meat-flies, Muscida ; Gnats and 

 Mosquitoes, Culicidce ; Long-legs, Tipulidce ; 

 House-flies, Anthomyia ; Hoverers, Syrphi- 

 dce; Gad-flies, Tahanidce. The African Tsetze, 

 Glossina morsitans, is a desideratum. 



Fleas, Pulicida, are inserted in this group because 

 of their resemblance to certain two-winged flies found 

 near the roots of trees in woods, Myceiopkilidce, the 

 larv8B of which infest various species of Agaricus and 

 other Fungi. 



Observe the eyes in Diopsis set at the ends of foot- 

 stalks ; the hymenopterous aspect of Mydas giganteus 

 and the extended proboscis of Pmigonia, capable it is 

 said of piercing the hide of cattle while the insect is 

 still on the wing. 

 Series of British species presented by Benjamin Cooke. 



Order LEPIDOPTERA. AeTr/j, a scale; Trrepov, 

 a wing. Wings four, covered on both sides with minute 

 imbricated scales. Estimated number of species, 24,000 

 (Bentham). 



The works used in naming and arranging the 

 series were numerous. Those of especial service were 



