120 CLASSIFICATION OF THE ANIMAL KINGDOM. 



We now come to the most interesting of all the classes we have yet 

 examined — that of Insects, the only animals of the articulated division 

 capable of flight; and, as was pointed out at the commencement of this 

 division, we find that, instead of an outward skeleton, composed of numer- 

 ous segments, they are here found condensed, and divided into only three 

 separate parts — the head, thorax, and abdomen. The former, which is 

 connected with the thorax by a moveable joint, containing the oral apparatus 

 and instruments of the senses. The thorax consisting of three segments, 

 united and supporting the legs, wings, and the abdomen, containing the 

 viscera. But before arriving at the perfect state, all insects undergo certain 

 metamorphoses, or changes from the egg to the caterpillar, thence to the 

 pupa, and after that to the imago or perfect insect, and these changes have 

 been variously classified by different authors. Professor Jones has selected 

 that of Burmeister, who calls the first division Insecta ametabola. 



The larvae or caterpillars of these animals resemble the perfect insect, 

 but have no wings, and the pupae of those which have wings in the 

 perfect state, possess rudiments of those organs. Some of this order have 

 "sucking mouths composed of four fine setae lying in a sheath," as the 

 Hsmiptera, a familiar example of which we have in the Water Boatman, 

 (JVotonecta,) so common in our ponds. The wings of this order, when 

 present, are four in number, and the upper pair generally half-coriaceous, 

 and the posterior portion membranous. Others have mouths with jaw- 

 like mandibles and maxillae, as the Ortlioptera, of which we have a familiar 

 example in the Gryllus domesticus, "the Cricket on the Hearth." This 

 possesses four wings, the posterior pair being larger than the upper, which 

 latter are of a dense leathery texture. A third order, the Dictyoptera, 

 a well-known example of which we have in the Cockroach, has four wings, 

 when they exist, and these are of equal size, and never folded. 



The second division, called the Insecta metabola, comprises those insects 

 whose larvae are possessed of legs, or without them, and the pupae is quiet, 

 or, if it moves, it does not eat. This division comprises the fourth order, 

 Neuroptera, with four equal reticulated wings, and strong lateral jaws. 

 The most perfect examples of this order are the Dragon-flies, though 

 these insects form exceptions to the general rule given above, as their 

 pupae are eminently blood-thirsty individuals. The fifth order, Diptera, 

 with little appendages, called poisers, in the place of posterior wings, and 

 sucking mouths provided with setae, and palpi, of which the common 

 House-fly forms a familiar example. The sixth order, the lepidoptera, 

 with four wings covered with beautiful scales, and a long sucking proboscis; 

 the representatives of which are too well known to need example. The 

 seventh order, the Hymenoptera, with four naked wings, traversed by 

 strong branching nervures, and larvae generally without head or feet; such 



