106 INTRODUCTION TO ZOOLOGY. 



been seen to outstrip and elude its swift pursuer of the fea- 

 thered class; nay, it can do more in the air than any bird; it 

 can fly backwards and sidelong, to right or left, as well as 

 forwards, and alter its course on the instant without turning." 

 These " limber fans" are of use in another capacity; they 

 take their share in the business of respiration, and hence 

 have been termed, from analogy, " aerial gills." 



From the great importance of the wings, and from the 

 modifications in their structure, they become naturally the 

 basis for classification; and without going much into details, 

 we shall endeavour to denote the principal groups of insects, 

 and notice their most striking characteristic features and 

 habits. 



Note Tn the brief outline, here given, we have, for the sake of 



simplicity, adhered to the Linnaean orders, with the additions of Orthop- 

 tera and Strepsipiera. Some of them, it may be proper to mention, have 

 been subdivided by modern entomologists. The meaning of the com- 

 pound term by which each order is designated will be given where the 

 term occurs: but it seems desirable, at the commencement, to place before 

 the learner, at one view, a list of all the orders hereafter mentioned, with 

 the literal signification of the names, and some well-known example of 

 the insects belonging to each division. Thus: — 



I. Coleoptera, sheath-winged, beetles, &c. 



II. Orthoptera, straight -winged, crickets, locusts, &c 



HI. Neuroptera, nerve-winged, dragon-flies. 



IV. Hymenoptera, membrane-winged, bees, ants, &c 



v. Strepsiptera, twisted-winged, stylops. 



VI. Lepidoptera, scale-winged, butterflies, &c 



VII. Hemiptera, half- winged, cicadas, water-scorpions, &c 



VIII. Diptera, two-winged, flies, gnats, &c. 



IX. Aptera, without wings, fleas, spring-tails, &c 



The first of these orders Coleoptera (page 107) was established by 

 Aristotle. The term is derived from two Greek words, meaning sheathed 

 or encased wings. Of Beetles, or Coleopterous insects, we have about 

 950 Irish species, according to the catalogue mentioned at page 92, and 

 referred to hereafter. It must be recollected that the numbers quoted 

 at any particular time, as belonging to the difi'erent orders, sliould be 

 regarded as showing the extent to which they had been investigated at that 

 period, and not as representing either the proportion actually collected, 

 or that probably existing. 



