44 OUTLINES OF NATURAL HISTORY. 



consist of an upper and lower lip, and of two pairs of 

 strong jaws. The jaws do not work up and down, as in 

 man, but from side to side, and they are adapted for bit- 

 ing, thus enabling the insect to live upon other insects, 

 which it captures and devours. 



Behind the head come three rings, which are slightly 

 separated from one another in the illustration (fig. 17, A, 

 t, t,' t"), but which in reality are consolidated with one 

 another so completely, that they can only be made out 

 by means of the appendages which they carry. They 

 compose collectively a region of the body which is known 

 as the chest or "thorax" (Greek, thorax, a breastplate). 

 The first of these three rings {t) carries a pair of jointed 

 legs ; the second {t') carries another pair of similar legs, 

 and a pair of wings ; and the third {t") carries a third pair 

 of legs, and a second j)air of wings. There are thus three 

 pairs of legs and two pairs of wings. 



The wings are really expansions of the skin, and are 

 nearly of equal size. They are membranous, transparent, 

 Avithoiit hairs, and rendered gauzy by an extremely fine 

 network of interlacing threads, which are known as 

 " nervures." These threads are really hollow ; and whilst 

 they serve to support the fragile expansion of the wing, 

 they also assist the insect in breathing, for they contain 

 blood-vessels and prolongations of the breathing-tubes. 



Behind the trunk or thorax comes the tail or " abdo- 

 men " (Latin, ahdo, I conceal ; so called because it con- 

 ceals the internal organs). This region of the body is very 

 distinctly composed of separate rings (nine in number), 

 none of which carry legs, and all of which except the last 

 are devoid of any appendages at all. 



Turning now to the internal anatomy of the Dragon-fly, a 

 few words may be said about its organs of digestion, its ner- 

 vous system, and its breathing and circulatory apparatus. 

 The mouth, armed with its powerful jaws, opens into a 

 gidlet (fig. 18, g), which conducts to a stomach (s). The 

 stomach opens into an intestine (i), at the commencement 

 of which are certain membranous tubes (/), which end 

 in closed extremities, and which are believed to represent 



