LOCUSTS. 27 



The extent to which these species are migratory, and the height 

 at which they fly vary according to the species and circumstances. 

 Acridium peregrinum travels for some hundreds of miles ; and 

 swarms, probably of this species, have been met with a thousand 

 miles out at sea. Their breeding places are generally dry and more 

 elevated plains. Their eggs are laid in the ground, in cylindrical 

 masses, coated with earth. Their natural enemies are birds, which 

 often follow the swarm and devour large numbers of them. Their 

 chief destroyers are, however, the grubs of the flies of the genus 

 Bombylius or its allies which devour their eggs. The grubs of 

 Blister-beetles also live on them. 



Some photographs are exhibited taken of a swarm of Acridium 

 peregrinum which occurred in Algeria, showing the methods taken 

 for entrapping them (fig. 24). The foreground of one of these 

 shows the remains of what was a cornfield. The barrier is made 

 of canvas, with a strip of American leather at the top, which being 

 smooth does not give the locusts a good footing. At intervals the 

 men shake the locusts off, and they are buried in trenches. 



The species which are occasionally found in Britain are Pachy- 

 tylus migratorius, P. cinerascens and Acridium per egrinum. Acridium 

 cegyptium (1293) has since 1898 been frequently found in and around 

 London, having been imported in vegetables (fig. 25b). 



Order NEUROPTERA. 



Sub-order Lsoptera. 



This case contains the commencement of the Neuropterous series, Table- 

 the lsoptera, White-ants or Termites (1300-1310). The meta- case 35 - 

 morphosis is gradual, incomplete. In some individuals there is 

 merely a difference in size between the young and adult. The 

 wings, when present, are four, folded flat on the back when at 

 rest ; the front and hind pairs are very similar in size and neuration, 

 which is of very simple character ; the distribution of the veins 

 is, however, strangely dissimilar in different genera. Near the base 

 of each wing there is a cross line where the wings are easily broken 

 off, the basal parts remaining as horny flaps on the insect's back 

 (fig. 26). The tarsi have four joints. 



The forms usually met with in a- " Termitarium," i.e. a com- 

 munity of Termites, are soldiers and workers without wings in all 

 their stages ; and special sexual forms which have wings when adult. 



