272 INTRODUCTION TO ZOOLOGY CHAP. 



Sub-order 2 : Saltatoria (The Jumping Orthoptera). 



Besides those Orthoptera which progress over the ground 

 by running, as the Earwig and Cockroach (Cursorial forms), 

 there is a large number specially modified for jumping 

 (Saltatorial forms). To this sub-order belong Grasshoppers, 

 Locusts, and Crickets. 



In all these forms, the body is laterally compressed, and 

 the hind legs are exceptionally strongly developed, since it is 

 by means of them that the insects leap over the ground ; also, 

 most of them " chirp," producing the sound with a special 

 musical instrument formed by the wing-covers and the third 

 joints of the hind legs (see below). 



Family 1 : ACRIDIIDAE (THE COMMON OR SHORT-HORNED 

 GRASSHOPPERS) 



The small Grasshoppers common amongst our grass during 

 the summer, which are so frequently to be heard and seen, 

 but are so very difficult to catch because of their extreme 

 agility, belong probably to one of the only three common 

 British genera of short-horned Grasshoppers. 



Genus Stenobothrus has delicate tapering antennae. 

 ,, Gomphocerus has club-shaped antennae. 

 Tettix .is peculiar because of the extension of the 

 first thoracic segment back ward over the abdomen. 

 It is common amongst dead leaves. 



All three genera are vegetable feeders only, and the female 

 lays her eggs in a little hole which she excavates in the soil. 



The musical organ with which the grasshopper chirps, 

 consists of a row of little bead-like projections on that side 

 of the femur next the body ; with these the grasshopper rubs 

 a prominent ridge on the outer edge of the upper wing, thus 

 throwing the wing into vibration and causing a musical note. 

 Only the males have this organ well developed, but it is 

 present in the females in a rudimentary condition. It is 

 known usually as the organ of " stridulation." 



An auditory organ, by which it is probable these sounds 

 are received, is present in the first segment of the abdomen, 

 lying just above the union of the hind leg and the thorax. 

 It consists of a little membrane or drum, surrounded more or 



