MORGAN HEBARD 183 



tion and marking that its racial validity is evident. The more 

 yellow Texas individuals, though the resemblance is purely 

 superficial, look indeed much like the yellowish specimens of 

 Melanoplus differ entialis (Thomas) which are also present there. 



From typical foedus fluviatilis it is distinguished by the aver- 

 age larger size and more robust form, the buffy or yellow caudal 

 tibiae and the postocular bar which is rarely solid, usually 

 decidedly broken and sometimes subobsolete. 



Like in the other races of foedus and in the related packardii 

 Scudder, the variation in coloration and intensity of the dark 

 markings is often great. 



A large series of foedus fluviatilis from Kansas averages large 

 for that race, the postocular bar is much more solid and promi- 

 nent, the caudal femora ventrad and internally are rich orange 

 in most of the dark individuals and buffy as in foedus iselyi 

 only in recessive specimens, while the caudal tibiae are glaucous 

 or pink, very rarely buff 17 and never yellow buff as is always 

 the case in richly colored typical examples of the present race. 

 A single female from Barber County, Kansas, is here listed as 

 atypical foedus iselyi, being in every way typical of it except 

 that the caudal femora are rich pink. 



Type. — 2 ; Weatherford, Texas. July 31, 1934. (F. B. Isely) . 

 [Hebard Collection, Type No. 1291]. 



Size large for the genus, form graceful but fairly robust. Vertex with 

 surface concave between the prominent lateral carinae, frontal costa at and 

 below the median ocellus similarly concave. Eye less than one and one- 

 half times as long as infra-ocular sulcus. Pronotum with medio-longi- 

 tudinal carina prominent on metazona, obsolete elsewhere; transverse sulci 

 distinct, averaging slightly more prominent than in joedus fluviatilis; 

 caudal margin of disk obtuse angulate produced with apex broadly rounded. 

 Organs of flight fully developed, well surpassing apices of caudal femora. 

 Prosternal spine erect, elongate cylindro-conical, with apex sharply rounded. 

 Furcula represented by small, strongly (rarely varying to moderately) 

 divergent, slender, tapering fingers, each several times as long as its width 

 beyond the thickened base. Supra-anal plate rather broadly shield-shaped; 

 its lateral margins moderately elevated to opposite the cereal bases, thence 

 straight convergent to the moderately acute apex; medio-longitudinal 

 concavity bounded by carinae which extend to near apex, lateral portions 

 concave. Cerci comparatively small, over twice as long as broad, tapering 



17 The few specimens known with caudal tibiae buff are all probably 

 teneral or discolored. 



TRANS. AM. ENT. SOC., LXH. 



