42 Key to Families of North American Insects. 



metathorax very large; fore wings reduced to small club-like 

 balancers; hind wings large, very delicate, with a few fine radiat- 

 ing veins. Female with the mouth-parts and antennae vestigial; 

 head and thorax fused into one piece, sexual openings in the form 

 of segmental usually unpaired canals opening on several of the 

 abdominal segments. 



1. Wingless, larviform, never leaving the host (Females) 2 



Winged, free living insects (Males) 4 



2. Spiracles more or less easily discernible, generally prominent; four or five genital 



tubes entering the brood canal; parasitic on bees, wasps and ants. (Stylops, 



Xenos) (PL 8, figs. 169, 172) XENID^E 



Spiracles not usually discernible, never prominent 3 



3. Tubercles of head apical; parasitic on Homoptera. (Agalliophagus, Antheri- 



c6mma.) HALICTOPHAGIIXE 



Tubercles of head more or less obsolete, ventral; only three genital tubes entering 

 the brood canal; parasitic on Homoptera (Fulgoroidea). (Mecynocera, 

 Pentagrammaphila.) ELENCHID^E 



4. Tarsi five-jointed, with two claws; antennae seven-jointed, the third and fourth 



joints produced laterally into long flabella; hosts unknown. (Trioxocera 



(Mexico)) MENGEID^E 



Tarsi with four joints or less, without claws 5 



-5. Tarsi four-jointed; antennae with only the third joint flabellate. (PL 8, figs- 



171, 175) XENID^E 



Tarsi three-jointed; antennae with the third or the third to sixth joints flabellate. 



(PL 8, fig. 170) HALICTOPHAGnXE 



Tarsi two-jointed; antennae with only the third joint flabellate. . .ELENCHID./E 



ORDER EMBIIDINA. 

 (EMBIOIDEA, EMBIOPTERA, OLIGONEURA.) 



Elongate feeble insects scarcely half an inch in length, occurring 

 in or near the tropics. Two pairs of similar wings superimposed 

 over the abdomen, or wingless; a pair of short anal cerci; first 

 joint of the front tarsi swollen and fitted for spinning delicate 

 tubular webs. 



1. Last dorsal plate of the abdomen not divided, nearly symmetrical, without 

 processes; first joint of left cercus simple, usually cylindrical; neuration 



complete. (Olyntha) (PL 8, fig. 174) OLYNTHIIXE 



Supraanal plate asymmetrical, deeply excised or divided, with processes 2 



2. Cerci slightly asymmetrical, first joint of left cercus simple, cylindrical, straight 

 or slightly curved or even clubbed, always without teeth on the inner side; 

 neuration strongly reduced. Posterior branch of the radial vein not forked 



