INSECTS, HARMFUL AND OTHERWISE 227 



this wayj however, but must leave the flower by one of two 

 openings near its base. In doing so it rubs against a pollen- 

 mass, which adheres to the insect's head or shoulder. When 

 the bee tries to get out of another flower it rubs off the pollen- 

 mass against the stigma, and in passing on takes along 

 another pollen mass. 



In many plants self-pollination is impossible, because the 

 stamens and pistils are in different flowers. This is the case 

 in the begonia, in the pumpkin, and many others. 



Some plants are so dependent upon insects that but for 

 them little or no seed would be formed. The common red 

 clover, generally poUinated by bumblebees, produces seed 

 only in small quantity if bumblebees are not about. 



Parasitic Insects 



Insects have many enemies and endure many hardships. 

 The rain and the cold kill great numbers, and moles, shrews, 

 bats, birds, frogs, toads, fish, etc. eat them. They are also 

 subject to disease. Attempts have been made to spread 

 contagion artificially among chinch-bugs and locusts, in order 

 to destroy them. Flies die from a fungous disease. Insects 

 prey upon each other. There are predaceous insects like 

 the dragon-fly, tiger-beetle, etc., that kill and eat many of their 

 fellows. Some insects destroy the hves of others by parasiti- 

 cally feeding upon or within them. All these checks upon 

 multiphcation are welcomed by man, providing they do not 

 affect our beneficial insects. And we consider insects useful 

 if they help us to get rid of the more harmful kinds. 



The little polka-dotted red or orange Ladybug is a very 

 useful beetle because it destroys great numbers of plant-lice, 

 scale insects, etc. It should be protected. One kind of lady- 



