CH. IX.] THE GALL-INSECT. 161 



of labourers, with here and there a huge soldier 

 that appeared like an ox among sheep ; other sol- 

 diers kept a foot or two from the column, apparently- 

 acting as videttes, appointed to guard against sur- 

 prise : others mounted the plants or blades of grass, 

 which flanked the main bodies, and, thus elevated 

 a foot and more, looked over and controlled the pro- 

 ceedings of the moving multitude. They turned 

 their heads in the different directions whence dan- 

 ger might arise, and every now and then struck 

 their forceps against the plant and produced the 

 ticking sound already mentioned, to which the 

 whole army answered simultaneously with a loud 

 hiss, and quickened their pace : after proceeding 

 thus for about fifteen paces, the two columns united 

 and sunk into the earth. The stream, however, 

 continued to flow on for more than an hour, during 

 which Smeathman watched their movements : the 

 rear was brought up by a large body of soldiers. 



CHAPTER IX. 



Parasitical Insects— Gall-Insect— Cochineal-Insect— T%e Scarlet 

 Colour used in Dyeing. 



We shall now proceed to the habits and instincts 

 of a class of insects which may with a little lati- 

 tude be termed parasitical ; some of these attach 

 themselves to the vegetable, others to the animal 

 kingdom. 



The history of the gall-insects is curious, chiefly 

 from the power they possess of diverting the laws 

 of vegetation from their ordinary into an extraordi- 

 nary track. These insects are not all of one kind ; 

 but, though differing in many respects, they have 

 this quality in common, that they deposite an egg 

 02 



