INTRODUCTION. 13 



The power of insects on the wing depends more on the size 

 of the thorax than either the size, form, or number of their 

 wings ; in other words, a monoplane is quite as good as a 

 biplane with sufficient engine power behind it. 



Of the Sialula or Alder flies (plate 8, fig. 80), we have only 

 one example Sialis /utirriaso common even-where, sitting 

 on fences or flying over the water. The eggs of this fly are 

 laid in patches on the leaves of marginal plants one patch at 

 times containing over ipooeggs and as they hatch, the lame 

 make their way down into the water, whence they emerge the 

 following year, and hatch on the surface into the well-known fly. 



II. Hymctwptcra (plate 8, figs. ;8, 79, 8 1-86, and plate 9, 

 figs. 96, 97) possess four wings, membraneous without scales, 

 never very large, the hind pair smaller than the front ; nervures 

 irregular in size and form ; mandibles conspicuous. The females 

 are furnished with a saw, sting, or ovipositor at the extreme 

 end of the body, which may be withdrawn into the body or be 

 permanently protruded. 



Hymenoptera are a very large class, including as they d<>, 

 many insects of such widely different habits. They are 

 popularly known as wasp-waisted flies, such being an easily 

 recognised characteristic. The ants, bees, wasps, ichneumon, 

 and gall flies, of which we use some few, and the saw flies are 

 included in this order. The hymenoptera are looked upon by 

 Entomologists as the most interesting and intelligent species 

 found in the insect world, containing as they do the bulk of 

 those which have communal existence and live in colonies, 

 where laws exist and the strictest discipline is maintained. 

 Many of the species are beautiful alike in form and colour. 

 Very few of them are aquatic insects, but man)' get on the 

 water accidentally. This is possibly one reason why at times 

 they are so attractive, as once on the water they buzz and make 

 a great fuss instead of quietly going ashore. If asked which 

 is our most beautiful fly, one would be puzzled to answer, but 



