THE MICROSCOPE AND INSECT LIFE 



final portion of its life before turning into the per- 

 fect fly. Within some of the pockets we shall find 

 the creature itself and it must be studied. Its head 

 is still ornamented with a pair of fans, but in this 

 case they are gills by means of which the insect 

 breathes and not food scoops, for it has reached a 

 stage when food is not taken. On its tail end there 

 is a hook, by means of which it anchors itself to 

 its slipper-shaped pocket. Probably we shall find 

 bubbles of air collecting round some of the insects, 

 within their pockets ; as the time approaches nearer 

 and nearer for the change to the perfect insect to 

 take place the bubbles grow larger and larger. 

 Eventually the fly emerges within a bubble, shakes 

 it free from the pocket and floats to the surface of 

 the water without wetting its wings. 



The pond will supply insects quite as interesting 

 as the running stream. Here we may find the eggs 

 of Caddis flies, enclosed in jelly-like envelopes, rope- 

 like, horse-shoe shaped or simple masses. The 

 caterpillar cases of these insects should be slightly 

 magnified and examined, for they are marvellously 

 constructed of shells or sand, pieces of stick, leaves 

 or other vegetation. 



We may come across the young stages of the 

 common gnat. Its eggs are very small and when 

 the mother gnat lays them on the surface of ponds 

 she glues them together so that they form what is 

 known as an " egg raft." The '' raft " we shall 

 notice, if we examine it carefully, is composed of 

 a large number of eggs; each egg is elongated, 



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