ORTHOPTERA 



395 



the sides of the first abdominal somite in the form of a small tympani- 

 form membrane. 



The destructive effects of locusts when appearing in swarms is well 

 illustrated in the case of the Migratory Locust (Pachytylus migratorius), 

 which is a native of Western Asia and Southern Europe. During 

 favourable weather these insects multiply to an enormous extent; this 

 leads to scarcity of food, and they are therefore forced to migrate (hence 

 the name) in order to find fresh pastures. Gathering in immeasurable 

 hordes, they wander forth, obscuring the sun, covering the country where 

 they alight far and wide, and in the briefest time consuming every bit of 

 green herbage. In Southern Eussia and Turkey such swarms are not a 

 rare phenomenon, but they have -also on several occasions spread their 

 devastations over Central Europe. Allied 

 species frequently make similar havoc in 

 Asia, Africa, and America. 



The third family of saltatorial Orthop- 

 tera consists of nocturnal insects living in 

 concealment, and therefore of dark colour. 

 They are the Crickets (Gryllidae), several 

 of which are capable of burrowing. 



The Mole Cricket (Gryllotalpa vul- 

 garis), as its name implies, represents the 

 mole among insects. Like the latter, it 

 digs out subterranean passages, and also 

 possesses a cylindrical body, supported on 

 short legs, the broad fore -limbs being 

 modified into digging spades. Since large 

 muscles are required to put these digging 

 instruments into operation, their thickness 

 and the extraordinary size of the first thoracic somite becomes intel- 

 ligible. The mole cricket deposits its numerous eggs in holes under- 

 ground, and then, in order that the sun may more effectively warm 

 the soil and consequently the eggs, the insect bites off the roots of 

 the plants growing above them, which consequently perish. But for 

 this one failing, the mole cricket would be considered among useful 

 animals, since its chief food consists of cockchafer grubs, and other 

 insect larvae and worms. It is easily got rid of by placing flower-pots in 

 its runs in such a manner that the insect is forced to drop into them. 



The thick-headed black Field Cricket (Gryllus campestris) inhabits 

 small holes, which it digs out for itself. The males of this species are 

 the untiring musicians of fields and heaths. 



The House Cricket (Gryllus domesticus) is a very similar insect, but 



HIND-LEG OF FIELD LOCUST 

 (Ste'iiobuthrus pratorum). 



, Row of chitinous teeth on the 

 inner side of the femur. Below : 

 Some of the teeth, strongly mag- 

 nified. (After Landois.) 



