Insects and their world 



long ones. The grasshoppers common to pastures and roadsides belong 

 to the first group, and so do the locusts of tropical countries; these im- 

 portant pests are a kind of short-horned grasshopper, which at certain sea- 

 sons bands together into a migrating swarm, and flies hundreds of miles, 

 alighting to feed each night, and devouring everything on which it settles. 



Long-horned grasshoppers (Fig. 14) are soft-bodied, more lethargic 

 insects, with whip-like antennae, and are generally found in bushes and 

 trees rather than among grass. Related to them are the crickets and the 

 mole-crickets: the last being powerful creatures with a big head and 

 powerful fore-legs, with which they dig energetically (Fig. 2). 



Many Saltatoria 'sing' or 'chirp': the technical name for it is stridula- 

 tion, from the Latin for a harsh, creaking sound. The mechanism is 

 described in Chapter IV, in the discussion of hearing in insects. 



8. Grylloblattodea. A small group of five species, scattered through 

 cold, mountainous areas of North America, Japan and Russia. Apart from 

 its rarity, chiefly interesting in linking up several closely allied Orders. 



^. Derma ptera (North America 20; world iioo) 



Earwigs, with the exception of the imported European earwig, are not 

 commonly encountered in North America. They are mainly active at 

 night, and during the daytime generally hide away under stones, or among 

 plants. They have a pair of curved forceps at the posterior tip of the body, 

 which look dangerous, but no one quite knows what they are used for. 

 Many earwigs have a pair of elaborately folded hind-wings, like a fan, but 

 strangely enough few people have ever seen an earwig fly. 



There is an old belief that earwigs crawl into the ears of people sleeping 

 outdoors, and since they are nocturnal and seek out small cavities for 

 concealing themselves, it is likely that this may be so. Two groups of 

 earwigs have become parasitic: Hemimerus feeds in the fur of African 

 rats (Cricetomys), while Arixenia is associated with Indian bats. 



10. Embioptera (North America 10; world 150) 



Web- Spinners are small slender insects which live furtively beneath 

 stones or under bark. They are chiefly tropical but a few species occur 

 in Southern United States. Their chief interest is that they spin silken 

 tunnels, using silk glands in the tarsi of the fore-legs (see Chapter II). 



11. Plecoptera (North America 350; world 1500) 



Stonefiies; Ferlaria (Fig. 3). These are soft-bodied, rather furtive 

 insects, the nymphs of which live in clear streams and lakes. The adults 

 do not fly much, and generally sit about among stones (hence the name), or 

 on water-side vegetation. The nymphs may be either vegetarian or carni- 

 vorous, and have tracheal gills (Chapter III) for breathing under water. 



12. Ephemeroptera (North America 550; world 1500) 



Mayflies (Fig. 4). The scientific name means 'living for a day', because 



12 



