172 INSECTS CHAP. 



few Insects, it is clear that a classification on the basis of 

 structure is the only one that can be at present of practical value. 

 We shall therefore for the purposes of this work make use of an 

 old and simple system, taking as of primary importance the nature 

 of the organs of flight, and of the appendages for the introduction 

 of food to the body by the perfect Insect. We do not attempt to 

 disguise the fact that this method is open to most serious 

 objections, but we believe that it is nevertheless at present the 

 most simple and useful one, and is likely to remain such, at any 

 rate as long as knowledge of development is in process of 

 attainment. 



Orders. 



The great groups of Insects are called Orders, and of 

 these we recognise nine, viz. (1) Aptera, (2) Orthoptera, (3) 

 Neuroptera, (4) Hymenoptera, (5) Coleoptera, (6) Lepidoptera, 

 (7) Diptera, (8) Thysanoptera, (9) Hemiptera. These names are 

 framed to represent the nature of the wings ; and there is some 

 advantage in having the Orders named in a uniform and descriptive 

 manner. The system we adopt differs but little from that 

 proposed by Linnaeus.^ The great Swedish naturalist did not, 

 however, recognise the Orders Orthoptera and Thysanoptera ; and 

 his order Aptera was very different from ours. 



These Orders may be briefly defined as follows, the reader 

 being asked to recall the fact that by a mandibulate mouth we 

 understand one in which the mandibles, or the maxillae, or 

 both, are fitted for biting, crushing, or grasping food ; while the 

 term suctorial implies that some of the mouth parts are of a 

 tubular form or are protrusible as a proboscis, which assists, or 

 protects, a more minute and delicate sucking apparatus : 



1 . Aptera (d without, irrepov a wing). "Wingless ^ Insects ; mouth mandibulate 



or very imperfectly suctorial. Metamorphosis very little. 



2. Orthoptera {6p66<s straight, Trrepov a wung). Four wings are present, the 



front pair being coriaceous (leather-like), usually smaller than the 

 other pair, which are of more delicate texture, and contract in repose 

 after the manner of a fan. Mouth mandibulate. Metamorphosis 

 slight. 



3. Neuroptei'a {vevpov nerve, Trrepov a wing). Four wings of membranous 



^ Sysf. Nat. Ed. 12, ref. i. pars ii. p. 536 (by error, 356). 



^ It must not be supposed that all wingless Insects fall within the limits of this 

 Order, 





