40 THE INSECT WOELD. 



nearly the whole of the head. Some have eyes of a brilliant 

 green colour, but looked at in certain lights they appear red. 

 Fig. 22 shows the head of the gnat with its two eyes, its antenna?, 

 and trunk. 



The instrument which the gnat employs for puncturing the 

 skin, and which is called the trunk (Fig. 23), is well worthy of 

 our attention. That which is generally seen is only the case of 

 those instruments which are intended to pierce our skin and suck 



our blood, and in which they 

 are held, as lancets and other 

 instruments are held in a sur- 

 geon's case. The case (Fig. 24) 

 is cylindrical, covered with 

 scales, and terminates in a 

 small knob. Split from end 

 to end that it may open, it 

 contains a perfect bundle of 

 stings. Reaumur tried to ob- 

 serve, by allowing himself to 

 Figs. 23 and 24. *> e stung by gnats, what took 



place during the attack. He 



forgot, in watching the operations of the insect, the slight pain 

 caused by the wound, soliciting it as a favour, his only regret 

 being not to obtain it when he wished. 



Reaumur observed that the compound sting, which is about a 

 line in length, enters the skin to the depth of about three-quarters 

 of a line, and that during that time the case bends into a 

 bow, until the two ends meet. He noticed besides, that the trunk 

 case of certain gnats was even more complicated than that which 

 we have described. But we will not dwell any longer on this 

 point. 



Let us now try to give an idea of the construction and com- 

 position of this sting, which after piercing the skin draws our 

 blood. 



According to Reaumur, the sting of the gnat is composed of 

 five parts. He acknowledges, however, that it is very difficult to 

 be certain of the exact number of these parts, on account of the way 

 in which they are united, and of their form. At the present day we 



