INSECTS : THEIR MOUTHS. 147 



In general, as we have seen, the macrillm are the specially 

 armed weapons ; the mandibles acting a secondary part, 

 often serving as mere sheaths in those insects which 

 pierce other animals with the mouth. But in this case 

 the mandibles are the favoured parts, the maxilla being 

 developed into broad leaf-shaped convex sheaths, inclosing 

 the mandibles. 



There are, however, two cutting blades besides.; the 

 labial palpi, which have their upper edge thick, divided 

 into four distinct joints, and set with bristles, thus re- 

 taining the proper character of palpi ; while their under 

 edge is thinned away to a fine keen blade, in which there 

 is no sign of jointing. Then there are the maxillary 

 palpi, of which the joints are furnished at their tips with 

 tiny projecting warts, doubtless the seats of a delicate 

 sense, and hollowed into a double series of chambers, 

 which are filled with a dark-coloured fluid. 



All this is very interesting to behold, and is calculated 

 to exalt our ideas of the wonderful and inexhaustible 

 resources of Omnipotence, as well as to humble us, when 

 we reflect how little we certainly understand even of 

 what we see. But, common as the Flea is, it is not a 

 matter of course that you will be able to repeat these 

 observations with the first specimen you put on the stage 

 of your microscope. Several favourable conditions must 

 combine in order to insure a successful examination. 

 You should choose a female Flea, partly because of her 

 greater size, and partly because the predatory weapons, 

 in all these piercing and sucking insects, are better de- 

 veloped in the females, — true Amazons. Then you will 

 find it needful to amputate the head, in order to get rid 

 of the front legs, the thick thighs of which else impede 

 your sight of the mouth, being projected on each side of 

 it. And this is a delicate operation; it must be per- 

 formed on a plate of glass, under a lens, with one of 

 those dissecting needles whose points are ground to a 



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