1890.] 57 



The following details of structure should be especially noticed : — 



The head has the vertex more or less produced between the antennse, and the 

 vertex may be broad and rounded {Dectlcus, &c.), or ending in a conical prominence 

 {Xiphldium), or of an intermediate form ; the edge of the vertex is separated from 

 the frons by a cross furrow ; the antennae have a very robust proximal joint, and 

 this is inserted in a cup, the form of which varies ; the eyes are more or less promi- 

 nent ; the lateral ocelli which the Acridiidce possess are wanting, and the central 

 one is an indistinct spot, situated immediately below the cross furrow, which separates 

 tlie frons from the vertex. 



In the thorax the pronotum shows some important characters, but is not so 

 useful in classification as it is in the AcridiidoB ; the longitudinal ridges are generally 

 wanting, but may be sometimes seen (Platycleis) , and the median one is obsolete or 

 not strongly marked. The structure of the side flaps should be noticed, especially 

 that of the inferior border, which sometimes runs backwards in a single curve to 

 meet the posterior border of the dorsal part (disc) of the pronotum, and sometimes 

 is more or less hollowed out over the shoulders, forming the " sinus humeralis." 

 Tlie prosternura may be plain {JSIeconema) , or furnished with two spines {Xiphi- 

 dit(in,&c.). The elytra have a much simpler venation than in the Acridiidce; 

 taking for example the elytron of Lo. viridissima, we see a mediastinal vein, an 

 anterior and a posterior radial vein, and an ulnar vein, and, springing from the last, 

 a dividing vein ; below this, in ^ , are two branches of the vena plicata, but in J , 

 part of the anal area with its veins is modified into a stridulating organ. The left 

 elytron when closed is carried above the right one, and in the upper or left part of 

 the apparatus the veins are thickened, especially on the under-side, and close to the 

 base of the elytron are two or three transverse strong veins, the outer of which 

 forms the internal border of an irregularly circular cell, the membranous part of the 

 elytron being unaltered, while in the right elytron this circular cell is filled by a 

 clear, transparent, glistening, vibratile membrane. By the rubbing together of these 

 two the sound is produced, and it is usually of a much shriller character than in the 

 AcridiidcB. 



The legs give most important characters. In the anterior tibiae, just beyond 

 the base, is situated what is said to be the external auditory organ, and of this 

 there are three forms : — ],open or oval (tympanum apertum), as in iI/eco«e)«a ; 2, 

 conchate (tympanum conchatum) ; 3, cleft-shaped (tympanum clausum), as in the 

 majority of genera. The disposition of the spines of the tibiae is -much used for 

 classification. The anterior tibice have a double row of spines below and a single 

 row above, and the presence or absence of apical spines in the upper row should 

 be noticed. The middle tibiae resemble the anterior ones, but lack the tympanums, 

 which these possess. The posterior tibiae have double rows above and below, and the 

 apical spines are of systematic importance. The majority of the Locustidcs have four 

 spines below, a pair on either side, which are used to fix a point from which the 

 insects spring, but in Phaneroptera there are only two spines, one on each side. 

 It should also be noticed whether the sides of the tibiae (ant.) and the sides of the 

 joints of the tarsi arc plain or sulcate. 



The structure of the genital apparatus should be noticed, especially that of the 

 supra-aual plate, sub-genital lamina, cerci, and ovipositor; the last differs fi'om that 



