INSECTS. 301 



with coloured liquid globules, and then two other wings gradually 

 appear. As soon as the wings are fully expanded, and have attained 

 their beautiful gauze-like texture, the dragon-fly begins to dart about, 

 and to catch any insect that may fall in its way. 



Equally rapid, exactly steered, and unwearied in its flight, is the 

 gnat. The wing of a gnat has been calculated, during its flight, to 

 vibrate 3000 times in a minute : these wonderful wings are covered on 

 surface and edge with a fine down or hair. 



The alternations of bright sunshine and rain which are common in 

 March, are extremely favourable to the appearance of gnats. The first 

 that appear are called the winter midges {Tricliocera hyemaMs). As 

 the spring advances, these midges are succeeded by others of a dif- 

 ferent species ; and as the weather becomes warmer, the true gnats 

 appear. The sting of the gnat {Culex pipiens) is well known ; though 

 gnats themselves are generally so rapid in their movements, and so 

 much dreaded, that very few people care to examine the delicacy and 

 elegance of their forms. The sting is very curiously formed (see fig. 

 134). The sucker is enclosed in a sheath, which folds up after one or 

 more of the six lancets have pierced the flesh ; it thus inflicts a severe 

 though minute wound, the pain of which is increased by an acrid 

 liquor injected into it through the curiously-formed proboscis, which is 

 covered with feathers or scales. A magnified view of one of these 

 feathers is seen at No. 3, fig. 134. A scale 

 from a gnat's wing is seen magnified 600 dia- 

 meters in Plate X. No. 7. The proboscis is 

 protected on either side by antennae, or feelers. 

 Those who will take the trouble to watch the 

 operations of the female (fig. 135), when she fig. 135. Female Gnat de- 

 is about to make her nest, will be very much positing her eggs. 

 struck with the ingenuity and admirable instinct which this little 

 creature displays. 



The bodies of insects are covered with a hard skin ; this answers 

 the purpose of an internal skeleton, and is one of their chief cha- 

 racteristics. All animals, and most fishes, have an internal skeleton 

 of bones, to which the muscles are fixed ; but the interior of an insect 

 is composed of a soft mass, and the muscles are affixed to the exterior 

 casing or horny skin, which answers all the purposes of bone, con- 

 necting the various parts, and maintaining them in their proper places ; 

 at the same time it is a perfect covering to the body. In some in- 

 sects this horny skin is remarkable for its strength, as in the beetle 

 tribe, many of which are exceedingly curious objects. 



