592 



HEMIPTERA-HOMOPTERA 



CHAP. 



known to him as being Lepidopterous, though he correctly 

 pointed out their distinctions. At present we can only con- 

 clude that the Aleurodidae undergo a metamorphosis of a kind 

 peculiar to themselves, and requiring renewed investigation. The 

 family has been monographed by Signoret, and more recently by 

 Maskell, who has increased the number of species to about sixty. 1 

 We have three or four in Britain, one of which, A. brassicae, is 

 extremely abundant on various kinds of cabbage in certain years. 

 Fam. 9. Coccidae (Scale -Insects, Mealy - bugs). -- Insects, 

 usually minute, with only a single claw to the foot ; the male with 

 one pair of wings, but without mouth-parts; the female wingless 

 and usually so degraded inform that most of the external orgu n* 

 and appendages cannot be distinguished. The form in which these 



Insects are most generally known 

 is that of a small scale or shell-like 

 body closely adhering to leaves, 

 fruits, or bark. The scales are of 

 the most varied form, so that no 

 general description can be given of 

 them. The scale may be defined 

 as an accumulation of excreted 

 matter, combined with the cast 

 skin or skins of the Insect, cover- 

 ing the body either totally or 

 partially, and thus acting as a shield 

 "a** whicl > ^ subsequent devel- 



a female scale magnified. (After opmeilt takes place. All Coccidae 



do not form scales ; but the habit of 



excreting a large quantity of peculiar matters to the outside of 

 the body is universal ; this excreted substance is frequently white,, 

 and of a powdery nature, and Coccids of this kind are known as 

 mealy-bugs. In other cases the exudation is like shell or glass, 

 and the creature may become quite encysted therein. In this way 

 the forms of Cocidae known as "ground-pearls" are formed. When 

 first hatched from the egg Coccidae are mite-like creatures, and it 

 is only subsequently that the females lose the power of loco- 

 motion. The females of numerous forms of Coccidae more 

 particularly the mealy-bugs do not lose the antennae and legs. 

 There is also a group (Brachyscelides) of Coccids that live in 



1 Tr. New Zealand last, xxviii. 1895. 



