' SOME USEFUL INSECTS. 243 



because if you do, you frighten it or make it 

 angry ; in either case you stand a chance of being 

 stung. 



Dragonfly. Don't kill a dragon fly. On warm 

 days you will see these beautiful flies with their 

 long bodies and gauze-like wings flashing like 

 jewels in the sunlight. 



They do not sting, are harmless, and do good 

 by eating many injurious insects, especially some 

 harmful butterflies and flies. 



Their larvae live in the water and feed on the 

 insects that they find there. They are said to 

 devour fish spawn and therefore in this respect 

 may be injurious. 



The gold eye lace flies, aphis lions, the ant 

 lion, and scorpion flies, all do good by killing 

 aphis and many harmful and irritating flies. 



You have read now of some of the useful 

 insects ; there are some others, but the ones you 

 have read about are the best known. 



How Insects Increase and are Kept in Check. 



Under favourable conditions of climate, abund- 

 ant food, and enemies not too numerous, an 

 insect will increase at an enormous rate. 



A female of the cabbage-white butterfly lays 

 about 200 eggs in heaps of 20 or 30, and she 

 goes through this performance twice a year. 

 Supposing half of these to survive and leave de- 



