BRANCH ARTHROPODA; CLASS INSECT A : THE INSECTS ij 1 



May-flics, the white ants and numerous other insects 

 have, like the locust, an incomplete metamorphosis, that 

 is, the young when hatched resemble in most respects, 

 except in the absence of wings,' their parents. 



The adult water-scavenger beetle feeds chiefly on 

 decaying vegetation in the water, but instances of the 

 taking of other insects and of snails have been noted. 

 Although an aquatic insect the beetle, like its larva, has 

 no gills for breathing the air which is mixed with the 

 water, but has to come to the surface occasionally to 

 obtain air. This it does in an interesting way, which 

 should be carefully observed by the pupils. The air is 

 received and held by a covering of fine hairs on the ven- 

 tral surface of the body, so that a considerable supply may 

 be carried about by the* beetle while underneath the sur- 

 face. The beetles often leave the water by night, flying 

 abroad to other ponds or streams. In winter the beetles 

 hibernate, burying themselves in the banks of the ponds 

 which they inhabit. 



For a good account, with illustrations, of the water- 

 scavenger beetle's life-history see Miall's " Natural His- 

 tory of Aquatic Insects," pp. 61-87. 



THE MONARCH BUTTERFLY (Anosia plexippns} 



TECHNICAL NOTE. The Monarch or Milkweed butterfly is dis- 

 tributed ail over the country. It is large, and red-brown in color, 

 and lays its eggs on milk weeds where the greenish yellow and black- 

 banded larvae (caterpillars) may be found feeding. The covering 

 of scales conceals the outlines of the various external parts, but 

 these scales may be easily removed with dissecting needle and a 

 small brush. In brushing the scales from the head care must be 

 taken not to break of the mouth-parts. 



External structure (fig. 41). Note the three body- 

 regions, Jicad, tJiorax and abdomen. Is the body seg- 

 mented ? Note the dark color and firm character of the 

 chitinized cuticle. 



