254 ARTHROPODA [CH. 



is always a quiescent pupal stage : Sialis the Alder-fly, much used 

 by anglers, Myrmeleon the Ant-lion, Hemerobius the Aphis-lion and 

 Chrysopa the Golden- eye lace-winged fly are examples of this order 

 found in Britain. 



Order IX. Coleoptera 



The Coleoptera (Gr. /coAeo'?, a sheath) or Beetles have mouth- 

 parts adapted for biting. The anterior wings termed elytra (sing. 

 elytron) are hard and horny and meet in the middle line of the 

 back in a straight suture and conceal the abdomen. The hinder 

 wings are membranous and folded and used for flight. There is a 

 grub-like larva with biting mouth-parts and a quiescent pupa which 

 takes no food. The metamorphosis is consequently complete. This 

 order has always been a favourite one with collectors, because its 

 firm exoskeleton renders preservation and identification easy, and 

 so the number of species of it named and described is much greater 

 than in the case of any other order of insects. At least 90,000 

 species are known. One of the most familiar British beetles is 



Coccinella, the Lady-bird, in which 

 the elytra are bright red in colour 

 diversified by black dots ; it is one 

 of the greatest friends of the 

 gardener, as it devours plant-lice. 

 The so-called Black-beetle as we 



have alread seen is not a Beetle 



FIG. 105. In the centre Coccinella 

 septempunctata, the Lady-bird at all but belongs to the Orthoptera, 



beetle, natural size, to the right, for example we dissect one of our 



larger British beetles such as the 



Cockchafer or June-bug (Melolontha) and compare its anatomy with 

 that of the Cockroach we cannot fail to be struck by the compara- 

 tive specialisation of the former insect as compared with the latter. 

 Thus in the Cockchafer the branches of the tracheae end in vesicles 

 (Fig. 106), the Malpighian tubes are reduced to two which are 

 beset with pouches; there is a huge tubular eversible organ, the 

 penis, for transmitting the spermatozoa to the female, and the entire 

 abdominal chain of ganglia is fused with and indistinguishable 

 from the last thoracic ganglion (Fig. 107). The reader should 

 compare with this the account given of the anatomy of the 

 cockroach on pp. 233 244. 



