72 ' Key to Families of North American Insects. 



densely gray dusted species, the abdomen usually marked with black or ,\ 



brown spots. (Ochthiphila, Leucopis.) OCHTHIPHiLID^ 



Costa interrupted near the end of the first vein; basal cells relatively large; 

 postvertical bristles divergent when present; arista pubescent; rather 

 slender, usually shining species with the antennae often very long and hang- 

 ing downward. (Chyliza, Loxocera, Psila.) PSILID.^ ^ 



79. Head folding back on the dorsum of the thorax; wingless flies parasitic on 



bats. (Nycteribia.) NYCTERIBirDiE 



Head sunk into the thorax, but not folded back, winged or wingless species, 

 parasitic on birds or mammals 80 



80. Palpi broader than long, projecting leaf-like in front of the head; wings when 



present with distinct parallel veins and outer crossveins; claws simple; 

 almost always parasitic on bats. (Trichobius, Strebla.) . . STREBLIDiE 

 Palpi forming a sheath for the proboscis; wings if present with the veins 

 crowded along the costa and with weaker oblique ones extending across the 

 wings; tarsal claws strong and often armed with a series of small teeth. 

 (Hippobosca, Olfersia, Melophagus [M. ovinus. Sheep-tick]) (PI. 11, fig. 

 257) HIPPOBOSCID^ ^ 



ORDER SUCTORIA. 



{SIPHON APTERA, APHANIPTERA, RHOPHOTEIRA.) 

 Small, wingless, strongly compressed, jumping insects, para- 

 sitic in the adult condition on warm-blooded animals; head small, 

 indistinctly separated from the thorax; antennae short and thick, 

 placed in depressions behind the small simple eyes which are some- 

 times wanting; mouth formed for sucking; thoracic segments not 

 fused; coxae large, close together; tarsi five- jointed; cerci one- 

 jointed; larvae worm-like; pupae enclosed in cocoons. Fleas. 



1. Thoracic segments not strongly shortened and constricted, their side plates 



extending over only one abdominal segment; labial palpi with three or 

 more false joints; maxillary palpi almost always shorter than the front 

 coxae; third joint of antennae with nine more or less distinctly separated 



false joints 2 



Thoracic segments strongly shortened and constricted, the metathoracic side 

 plates extending over two or three abdominal segments; head strongly 

 angulated anteriorly; labial palpi without false joints; maxillary palpi 

 extending beyond the front coxae; third antennal joint without completely 

 separated false joints; fully developed female with enormously dilated 

 abdomen, living beneath the skin during her final development. (Derma- 

 tophilus (= SarcopsyUa, = Rhynchoprion) [D. penetrans. Jigger-flea]) (PI. 

 13, fig. 310) {SARCOPSYLLIDM, RIIYNC OPRIONID/E). 



DERMATOPHILIDiE 



2. Maxillae triangular, acute at apex 3 



Maxillae clubbed or subquadrangular; face strongly sloping forward and recurved 



just above the mouth, where there are two tooth-like plates on each side; 



