THE COCCI D.'E. 383 



curious white cottony stuff which encircles them and protects them 

 from the air. When we crush this white mass the Aphis within it 

 bursts, and a red stain is produced hke blood. Some others live 

 in groups, which are enclosed in the galls which they produce by 

 irritating the structures of certain plants. 



The family of the CcccidcB are very closely allied to the 

 Aphides, and are frequently called scale insects or mealy bugs. 

 They are very interesting, and may be easily distinguished from 

 the plant lice. The development of the Coccidcs does not progress 

 so regularly as it does in the Aphides, and it stops short, and 

 even retrogrades in most remarkable manners. They do a great 

 deal of harm to vegetation ; but some, such as the cochineal 

 insects, are most useful to man, on account of their furnishing 

 magnificent colouring matters and inducing commerce. 



In the engraving on page 381 the rounded scale-like insects on 

 the cactus are females. The female Cocci possess a certain amount 

 of activity when they are born, and they search out leaves and twigs 

 or stems upon which they intend to feed. Having made up their 

 minds they stick their sucker into the tissue of the plant, and can 

 never take it out again. They are found firmly attached to it, and 

 it will be noticed that they gradually lose all trace of the articula- 

 lations of the body, that they become motionless and apparently 

 senseless, so that they resemble vegetable excrescences. They are 

 always sucking, and even their courtship is spent whilst they are 

 imbibing the juices of the plant beneath them. They lay a large 

 quantity of eggs, and produce a greater or less abundance of a 

 cottony matter. The o.^^ laying goes on without any movement 

 on the part of the mother, and when she dies her body dries up and 

 often forms a shelter for the newly born creatures. The larvse, as 

 soon as they are born, spread over the branches and leaves, and 

 remain there during the warm weather. They are usually very 

 small, but they increase to such an extent that the death of the 

 plant becomes almost certain. It appears that they are repro- 

 duced somewhat like the Aphides, but only the males have wings. 



The engraving on page 382 represents the males of the co- 

 chineal insect highly magnified. 



