ENEMIES OF PLANTS. 303 



(c) It will be interesting and instructive to place the 

 ]arva and the adult forms of the ladybug, and of the 

 lace-winged fly in the breeding-jars, and supply them 

 with portions of plants infested by aphides, and watch 

 what takes place. 



(d) In which of these stages did your specimen of 

 ladybug devour the plant-lice ? How ? 



(e) In which of these stages did your specimen of lace- 

 winged fly devour the plant-lice ? How ? 



XI. Specific Examples of Injurious Insects. 



i. Plant-lice are among the most familiar and 

 most annoying of the insects injurious to plants. 

 The family includes many species, all of which 

 are small, the largest measuring only one-fourth 

 inch in length. Most of those we see are wing- 

 less, but some of the common species have two 

 pairs of transparent wings. Our most common 

 species of plant-lice are green or black, but 

 others are red, brown, or yellow. The beak is 

 three-jointed. It is not coiled up like that of 

 the butterfly, but is attached to the head by a 

 hinge, and is bent up against the under side of 

 the body when the insect is not feeding. They 

 feed upon the buds, leaves, and tender growing 

 stems or roots of plants, and in such immense 

 numbers as to often do much damage. 



EXERCISE 15. It will be easy to find colonies of these 

 plant-lice upon crysanthemums, cherry, or plum sprouts, 

 or even roadside weeds. 



(</) Watch them closely, taking care not to dis- 

 turb them. What other insects do you see among 

 them ? Do you find two tiny tubes projecting from the 



