154 THE CAUSES WHICH PROPAGATE 



red twilight, there arises all at once that weird and dreadful 

 whistling of the great Green Leaf-cricket on the dusky top of 

 the oaken spray, which in our younger days has so often induced 

 us to quicken our steps homeward over the burnt heather, arising 

 like the prophet at sunrise, to find this Gob Gobim vanished, or 

 the solitary place of its hiding at most betrayed by a momentary 

 chirp, and the feathered tribes again asserting their despondent 

 supremacy of song. 



In the musical species of saltatorial Orthoptera, where the 

 males are uiiiformly pugnacious with cannibal females, the pre- 

 eminence of this character seems to predispose higher capacity 

 for stridulation ; for which we may seek parallel in the long- 

 horned beetles, while a masculine diiferentiation of music indi- 

 cates migratory banding of the species. Thus, the tribe of Locus- 

 tina, whose females are discriminated by sabre-shaped ovipositors 

 serrated at the extremity, has males with alar musical organs 

 highly organised, although, indeed, a few species are mute, and 

 the females of others crepitate. In Leaf- crickets, as in Crickets, 

 stridulation results from sexual differential development of the 

 semi-elytra, which in the male of the latter mostly correspond ; 

 while in the former, the formation of the musical organ^s two parts 

 is usually accompanied with diverse development of the anal 

 fields, and induration or expansion of their veins and membrane. 

 In many species^ a /shaped lima (Plate II., Fig. 5, b, /) — helically 

 prominent on an inwardly-grooved outwardly-bowed transversal 

 branch of the anal vein, and depressed beneath the left elytron's 

 coriaceous elastic membrane — presents a serried row of obliquely 

 parallel parallelopiped dentations (Fig. 4, c) , small and soft at 

 its extremities, elongate, black, and indurated at its centre; 

 apparently abnormal excrescences of the tracheal thread, or as Herr 

 Vitis Graber affirms, modifications of the scaly membraneous folds 

 that cover the wings and body. These are fiddled obliquely 

 over the rounded, raised, and incrassated inner basal edge of the 

 right elytrons, near which is a tense and transparent iridescent 

 talc-like spot, embossed superiorly on the anal field in fashion 

 of a blue spectacle- glass, exteriorly to the rudiments of an un- 

 indurated lima {sm, Fig. 5a). As in musical insects generally, 



* Locusta [Phasgonura, Westw.) ; Thamnotrizon, Fisch. ; Decticiis, Ser. ; 

 Choloccelus. 



