HEMIMYLACRIS. 121 



of the wing becomes central, instead of being in front of the wing-axis as in 

 the Archimylacridae. The principal veins and their branches show a greater 

 tendency to pass straight outwards to the wing-margin than in the Archimylacridae, 

 while the pronotnm has become broader and shorter, and assumes more of a 

 reniform appearance. 



The wing-surface is leathery and coriaceous, and often cross-wrinkled. Pruvost 

 states that the interstitial neuration is composed of a fine network of nervures, 

 which is more correct, the thickened wrinkled condition being a later development. 

 The body is broad and flat. 



Handlirsch regards the Mylacridre as an early, extremely developed, lateral 

 branch of the Blattoid series, and thus still retaining rather primitive characters, 

 best seen in the median vein. Handlirsch adds (190G, ' Proc. U.S. Nat. Mus.,' 

 vol. xxix, p. 7GG) : "Perhaps they owe their origin to an adaptation to their 

 environment, for it is remarkable how similar many of them are to certain leaves 

 of ferns, with which they are generally found (a fact to which Scudder had already 

 drawn attention). Probably they lived under deciduous fern-fronds, and by their 

 similarity to the pinnae were protected from their enemies." 



Pruvost (1920) considers that the Mylacridae may constitute a well individualised 

 phyletic series which sprang late from the Archimylacrid stock. He divides the 

 family Mylacridae into two divisions, Hemimylacridian and Mylacridian, the former, 

 as typified in I'li-i/Jomylarris and Hemimylacris, being really intermediate forms 

 lying between the true Archimylacrids and the true Mylacrids (Mylacridians), and 

 more nearly descended from the first. Pruvost also points out that Handlirsch has 

 placed Apojphthegma (the Hemimylacris of Saxony) with the Archimylacriclge, and 

 the American members of the Hemimylacris among the Mylacridae. He is some- 

 what uncertain whether to place the Hemimylacridians with the Archimylacridae 

 or with the Mylacridae, but decides in favour of the latter, suggesting that both the 

 Hemimylacridians and the Mylacridians are of polyphyletic origin. 



Genus HEMIMYLACRIS, Handlirsch. 

 1900. Hemimylacris, Handlirsch, Proc. U.S. Nat. Mus., vol. xxix, p. 767. 



Generic Characters. — Wings twice as long as wide. Costal area broad, in one 

 species almost triangular, in another somewhat strap-shaped. Radius with four 

 outer branches, the first dividing into two or three twigs. Median with three 

 branches directed inwards. Cubitus with 4 — 5 branches which do not occupy the 

 whole of the free inner margin. Anal area two-fifths the length of the wing, and 

 more than twice as long as wide. 



Handlirsch remarks that this genus may be classed almost as well with the 

 Archimylacrida? as with the Mylacridae, thus agreeing with Pruvost. 

 16 



