INSECTS : THEIB MOUTHS. 145 



and such elaborate contrivance is displayed for the comfort 

 of an obscure and offensive insect, by Him Who has not 

 disdained to exercise His skill and wisdom in its creation ! 



You know the stout flies which are denominated Horse- 

 flies or Whame-flies (Tabanus), which are so numerous in 

 the latter part of summer, flying around horses, and men 

 too, if we intrude upon their domains. They are con- 

 tinually alighting on the objects of their attentions, and 

 though driven away, returning with annoying pertinacity 

 to the attack. You may always recognise them by the 

 brilliant metallic hues — reds, yellows, and greens — with 

 which ,their large eyes are painted, often in stripes or 

 bands. These are voracious blood-suckers ; and, as might 

 be supposed from their propensities, they are well furnished 

 with lancets for their surgery. Here you may see their 

 case of instruments, which are so effective, that Eeaumur 

 tells us that, having compelled one to disgorge the blood 

 it had swallowed, the quantity appeared to him greater than 

 the whole body of the insect could have been supposed 

 capable of containing. 



All the parts here are formed of the common amber- 

 coloured chitine, brilliantly clear and translucent. The 

 upper lip forms a sort of straight sheath, in which all the 

 other parts are lodged when not in use. The mandibles 

 are narrow lancets, of which one edge near the tip is beset 

 with reverted saw-teeth, and the opposite edge with 

 exceedingly sharp points standing out at right angles ; 

 while the surface is roughened with lozenge-shaped knobs 

 set in regular rows. Below these are the maxilla, which 

 are the principal cutting instruments ; these are shaped 

 like a carving-knife with a broad blade, strengthened at 

 the basal part of the back by a thick ridge, but brought to 

 a double edge near the tip. The back-edge is perfectly 

 fine and smooth, so that the highest powers of the micro- 

 scope can only just define its outline, while the other edge 

 is notched into teeth so delicate that twelve of them are 



