32 



This section of the old genus Acridium is divisible into three 

 groups, represented respectively by the familiar species, Acridium 

 dux (Drury), A. carinatum (Stoll'), and A. Olfersii Burm. A. crista- 

 tum (Linne) falls into the first group, althougb the almost total 

 absence of a median crest on the posterior prolongation of the prono- 

 tum, as well as several minor characters, separate it from other 

 members of the same division. 



These three groups seem to be of generic value, and since A. far- 

 taricum (Linn.) Ollv., ought to be taken as the type of the genus 

 Acridium proper, they must all be separated from that genus and 

 may be called respectively Tropidacris, Titanacris and Lophacris. 



TKOPIDACRIS (rpon'ig, tcxqlg). 



Head large, compressed ; space between eyes equal to the shorter 

 diameter of the eye;^ median frontal ridge broader than the length o^ 

 the first joint of the antennae ; the breadth of the labrum is equal to 

 the distance from the upper edge of clypeus to the upper limit of the 

 median frontal ridge, or one and one half times the longer diameter 

 of the eye (see previous note), or fully one and one half times 

 broader than long; the lateral angles of the front are distinct diver- 

 gent. Pronotum tapering moderately, — the breadth anteriorly being 

 to that posteriorly as 1 : 1 . 2 ; the angle of the posterior border is a 

 right angle or less ; the median crest Is much more prominent ante- 

 riorly than posteriorly, sometimes obsolete behind; the prosternal 

 thorn rather slender, barely compressed laterally, inclined backward 

 a little, the tip curved slightly backwards and pointed. Tegmina 

 fully five and one half times longer than broad, the costal edge nar- 

 row; secondary veins very prominent; internomedian vein furcate; 

 basal branch of the externomedian vein simple, but united by distinct 

 cross veins to the Internomedian vein. Wings long and broad, 

 largely spotted with dusky colors ; cross veining at tip scarcely more 

 frequent than in other parts of the wing, and perfectly regular ; the 

 area between the first and second branches of the anal vein not 

 noticeably broad, broken by cross veins into spaces not more than half 

 as long again as broad (9), or noticeably broader than the adjoining 

 ai-eas, broken by cross veins Ii\to spaces twice as long as broad (<5) ; 

 second branch of anal vein regular, sending downward one jij-imary 



1 The eyes in the male of T. Fahricii are very large, and hence the space between 

 them is a little less than the shorter diameter of the eye; and the breadth of the 

 labrum is equal to only one and one fourth times the longer diameter of the eye. 



