SYA^OFSIS. XXI 



"Diptera," 253. Strength of wings and size of mesothorax cor- 

 related with swift flight, 253. Alulets, 253. Halteres, 253, 

 Gradual reduction in size and efficiency of the hind-wings in 

 passing from the Lepidoptera to the Hymenoptera and Diptera, 

 this change correlative with the reduction of the wing-bearing 

 segments and their muscles, 253. Cause of the buzzing of the 

 fly, 254. Larval characteristics of Tabanus, 254. Development 

 of Musca domestica, 254; larva not a generalized but an ex- 

 tremely specialized form, shape of body adapted for boring, 254; 

 forward end of body not differentiated into a head, 254. Brief 

 duration of larval and pupal life, 255. Time of appearance of 

 the imago, 255. Brauer's classification of the Diptera based 

 upon larval and pupal characteristics, 255. Position of the semi- 

 parasitic fleas and true parasites, 256. Tipulidse, 257. Resem- 

 blances of the adult to Lepidoptera, 257. Thoracic region wholly 

 exposed, 257. Absence of a sting the probable cause of absence 

 of pedunculated abdomen, 258. Presence of an external, horny 

 ovipositor, 259. Biting mouth parts and diet, 259. Resem- 

 blances of Tipulid larvae to the generalized larval forms of Lepi- 

 doptera and Hymenoptera, 259; resemblances to the specialized 

 larvae of Hymenoptera, 259. Culicidae, 259. Thoracic region 

 shortened but wholly exposed, 259. Dimmock on the mouth 

 parts and diet of the Culicidae, 260, 261. Eggs of mosquitoes, 

 261; larvje with differentiated head and abdominal respiratory 

 tubes, 261. Thoracic breathing-tubes of pupa, 261. Motions 

 of pupa produced by muscles of abdomen, 261. Asilidae, 262. 

 Posterior part of thoracic region partly concealed, 262. Carniv- 

 orous habits of robber-flies correlated with peculiarities of struct- 

 ure, 262. Tabanidffi, 263. Extreme concentration of parts of 

 body, 263; posterior portion of thorax entirely concealed, 263. 

 Cecidomyidas, 263. Aberrant characters of family, 263. Resem- 

 blances to Hymenopterous gall-flies, 263. Degraded structure 

 of mouth parts, 263. Peculiar mode of escaping from the 

 puparium, 263. Cyclorhapha, 264. Junction of the abdomen 

 in Syrphus, 264. Larvae without a differentiated head, 265. 

 Habit of devouring Aphides correlated with sucking mouth 

 parts, 265. Rat-tailed larva of Eri stalls tenax, 265. Muscidte, 

 265. Junction of abdomen in Musca, 265. Kraepelin on mouth 



