94 NORTH AMERICAN ACRIDIDAE (oRTHOPTERa) 



Radinotatum minimipenne (Caudell) (Plate IV, figures 5, 6 and 7.) 

 1904. Achurum minimipenne Caudell, Sci. Bull., Mu.s. Brooklyn Inst. Arts 

 and Sci., i, p. 110, pi. vi, figs. 3 and 4. [9, Brownsville, Texas.''] 



The type is in the collection of the Museum of the Brooklyn 

 Institute of Arts and Sciences. 



As Caudell has stated, "this species seems to form a con- 

 necting link between Achurum and Radinotatum." Nearer 

 affinity is, however, with the latter and, from study of the 

 material before us, we feel fully justified in transferring minimi- 

 penne to that genus. 



The vertex is much like that of R. brevipenne (Thomas), the 

 lateral margins not overhanging and less convergent than is 

 normal in Achurum. The lateral foveolae are subobsolete, 

 agreeing with brevipenne in facing laterad, with delimiting ventral 

 carina indicated only distad; in Achurum the lateral foveolae 

 face ventro-laterad, with delimiting ventral carina indicated 

 only mesad. The caudal margin of the pronotum is not concave 

 as in brevipenne, nor is it nearly as strongly angulate-produced 

 as in Achurum. It is very possible that the differences shown 

 in this feature in these species, is wholly attributable to modifi- 

 cation resulting from degree of reduction of the organs of flight. 

 Such difference should, in consequence, be given little generic 

 value. In the genicular lobes of the caudal femora we find 

 much closer agreement with brevipenne, the dorsal pairs being 

 decidedly the more produced, the dorso-internal the longer. 

 In brevipeiine the only difference is that the production of the 

 dorsal lobes is much greater. Similar closer affinity is found in 

 the form of the male subgenital plate. The dorso-external 

 spines of the caudal tibiae vary individually in number from 

 fourteen to seventeen in the material here recorded, the average 

 being sixteen.^ When we consider that brevipenne has from 

 sixteen to twenty-three such spines, and Achurum thirteen to 

 seventeen, we see that this feature is of little value from a gen- 

 eric point of view. 



The genera Achuriun and Radinotatum are close, but the for- 

 mer, as here limited, may be quickly separated by the structure 

 of the fastigiuin of the vertex, of its lateral foveolae and the 

 proportions of the g(nii('ular lo])es of the caudal femora. 



^ Both sexes were at tlie same f imc recorded from Esperanza Ranch, near 

 Brownsville, Texas. 



^ In one specimen from Tampico, Tainaulii)as, Mexico, one of the caudal 

 tibiae has nineteen sucli spines. 



