INSECTS 351 



cially as there are not the same obvious distinctions as are found 

 in some other groups, e.g. Molluscs. Various subdivisions have 

 been proposed, some of the modern ones being complex, but it 

 will be the simplest plan to adopt here the comparatively old- 

 fashioned grouping into nine orders, primarily based upon the 

 characters of the wings, and which is mainly due to Linnaeus. 

 It will be enough for the present purpose if some of the commonest 

 insects are mentioned, and sufficient detail given to enable the 

 reader to refer an insect to its proper order. 



Order I. Bugs (HEMIPTERA). Four wings, of which the front pair are 

 often only membranous at the tips. 



Order 2. Fringe-winged Insects (THYSANOPTERA). Four wings, all 

 very narrow and fringed. 



Order 3. Flies (DlPTERA). A single pair of membranous wings equiva- 

 lent to the front pair of other insects. 



Order 4. Moths and Butterflies (LEPIDOPTERA). Four wings present, 

 covered with scales. 



Order 5. Beetles (COLEOPTERA). Four wings, of which the front ones 

 are converted into hard wing-cases, covering the membranous hind-wings, 

 which during repose are folded transversely. 



Order 6. Membrane-winged Insects (HYMENOPTERA). Four mem- 

 branous wings possessing but few nervures, and which cannot be folded up. 

 Fore-wing larger than the hind. 



Order 7. Net -winged Insects (NEUROPTERA). Four membranous 

 wings, with an elaborate net-work of nervures. 



Order 8. Straight- winged Insects (ORTHOPTERA). Four wings, of 

 which the front pair are horny wing-cases, while the others are membranous 

 and fold up in a fan-like manner when at rest 



Order 9. Wingless Insects (APTERA). Primitive wingless insects. 

 Insects belonging to other orders may have lost their wings by a process of 

 reduction affecting one or both sexes. 



Order i. BUGS (Hemiptera) 



The English name given to the order is somewhat libellous, 

 for though a number of repulsive forms are included here, others 

 again are beautifully coloured and attractive objects. A typical 

 species is outlined in fig. 203. There is considerable variation 

 in the matter of wings, as both pairs may be much alike, or the 

 fore-wings may be wing-cases, or again both pairs may be absent. 

 In all cases the mouth-parts are converted into piercing and 

 sucking organs, which, though much unlike the corresponding 



