BRITISH INSECTS 



2. Sub-Order Plecoptera (Stone Flies) 



The Stone Flies belong to the family Perlidce, and they 

 also have an incomplete metamorphosis. They are 

 fair-sized insects, with long slender antennae. It should 

 be noted that the hind wings are larger than the front 

 pair. The larvae are water-dwellers, and they subsist 

 upon both decayed vegetable substances and animal 

 food. When the larva is full-grown it crawls to land, 

 the skin splits along the back, and the perfect insect 

 emerges. This latter frequents trees, and is very active. 



3. Sub-Order Sialida (Alder Flies) 



The Alder Fly {Sialis lutaria, Figs. 23 and 24), is in- 

 cluded in this Sub-Order, and unUke the foregoing, it 

 has complete metamorphoses. The adult has the head 

 embedded in the prothorax, and it has long and slender 

 antennae. The two pairs of wings are of different 

 shape. As a rule the eggs are laid on various plants 

 near water, and as soon as the larva hatches, it makes 

 for the liquid element, where it spends its time in the 

 mud feeding upon small aquatic creatures. The body 

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