May, 1953 Burks: THe Mayrties or ILLinots 145 
Gills are borne by abdominal segments 1-7, 
but the structure of these gills varies greatly 
era, the body is elongate and fishlike, but in 
Pseudiron, it is flattened dorsoventrally. 
Sil 
309 310 
Fig. 301.—Pseudiron centralis, hind leg of mature nymph. 
Fig. 302.—Siphloplecton interlineatum, middle leg of mature nymph. 
Fig. 303.—Siphloplecton interlineatum, fore leg of mature nymph. 
Fig. 304.—Pseudiron centralis, gill of third abdominal segment. 
Fig. 305.—Siphloplecton interlineatum, head of adult male, lateral aspect. 
Fig. 306.—Siphloplecton interlineatum, terminal abdominal sternites of female. 
Fig. 307.—Pseudiron centralis, terminal abdominal sternites of female. 
Fig. 308.—Siphloplecton basale, wings. 
Fig. 309.—Siphloplecton interlineatum, male genitalia. 
Fig. 310.—Pseudiron centralis, male genitalia. 
Fig. 311.—Siphloplecton basale, male genitalia. 
