HEMIPTERA. 



473 



The Pentatoma oleaceiim (fig. 1044) is another plant-destroying 

 insect, which is often noticed on vegetals. 



The family of Aphides is injurious to the gardener. Some live 

 upon the leaves of plants, and suck their juices. Other kinds, as the 

 Oak Aphis, live on the trunks of trees, which they pierce, and suck 

 their juices. Some live upon the tops of young shoots, as the Rose 



Fig. 1044. — Pentatoma 

 oleaceum. 



Fig. 1043. — Lygus solani and Lygus umbellatarum. 



Aphis ; and others feed underground, and suck the roots of plants, 

 as one species which infest the lettuce. When aphides attack a plant, 

 it has a tendency to rot at the roots, and I have even known large 

 willow-trees to die down and rot after a severe attack by aphides. 

 Gardeners are generally too tardy in the destruction of these creatures ; 

 the instant they appear they should be killed with tobacco smoke. 

 Melon and cucumber plants frequently perish from the attacks of 

 these creatures, as they remain unnoticed on the under surface of the 

 leaves. 



The aphis exists in three states, — the larva, the pupa, and the winged 

 or perfect insect. It multiplies with extreme rapidity, and in the 

 winged state frequently appears in vast clouds, filling the air and 

 settling upon every object. Eggs are laid at the end of the year by 

 some specie.s, and I have hatched eggs experimentally in warm houses, 

 to be sure that they were the eggs of aphides. It is a remarkable fact 

 that the females propagate to an unknowii extent without impregna- 

 tion ; and although I have kept myriads of the Aphis vastator for 

 observation, I have never seen either an &gg or a male. We are in 

 the habit of looking to astronomy for numbers beyond the capacity of 



