79 



No part of a plant seems to be exempt from their attacks ; driving their sharp Beaks 



tlirough the epidermis, they suck the sap from the leaves, the young twigs, the roots, and 



, even the rough bark of the stem. A good 



represensation of a too common species, A. itiafi, 

 the apple blight, is given at Fig. 90, and illus- 

 trates the structure of most of these insects ; we 

 have the winged male of the natural size and the 

 same with the female magnitied. The best 

 remedy for all the small insects which affect the 

 bark and foliage of trees, is undoubtedly a fre- 

 quent application of a solution of whale oil soap 

 thrown on to the foliage by means of a syringe. 

 The bark-lice which swarm on apple-trees in the 

 autumn may be easily cleaned off by means of a 

 "" I'i". 90. thorough scrubbing with soap-suds ; the addition 



of flour of sulphur to this mixture will prevent 

 fungoid diseases making way where the Apliides have injured the bark. Many of the 

 species make galls on different plants as on the poplar. The injuries done by these 

 minute flies, I have said, is very great. Kirby and Spence state that the damage done to 

 hops alone in England often made as much difference as £200,000 in the duty on hops in 

 one year. I have myself occasionally seen in the south of England, what gave promise of 

 being a splendid crop of hops, rendered worthless by a species of Aphis, in the short 

 period of about a fortnight. It is to this family that the dreaded Phylloxera belongs which 

 has absolutely rendered the cultivation of the vine impossible in some parts of France, and 

 I know from personal information that a large grape-grower in one of the best champagne 

 districts in that country had, in 1880, on account of this insect, simply to give up vine- 

 growing, grub up his vineyards, and burn the vines. 



Our President has so ably described this insect in its different forms in several papers 

 during the past year or two that further reference to it is unnecessary. 



In the last division, Monomera, which have only one joint in the tarsus, we find those 

 extraordinary insects the Coccids, or Scale insects, as they are called, on account of the 

 peculiar shape of the females, which in different species take different forms ; some are 

 oval and more or less convex, some shaped like a boat turned bottom upwards, some 

 kidney shaped or globular ; and one of the best known, the oyster-shell bark louse, takes 

 the shape its name implies. Westwood remarks truly : "These form one of the most 

 anomalous tribes of insects with which we are acquainted, and which already prove that 

 annulose animals may exist, which become more and more imperfect as they approach the 

 winged state, and which in that state lose all trace of articulation in the body as well as 

 of articulated limbs (as in the female Cocci), leaving, in fact, inert and fixed masses of 

 animal matter, motionless and apparently senseless, and which resemble nothing more 

 nearly than the vegetable excrescences called galls." 



The females undergo only a partial transformation, and never possess wings ; the 

 males on the other hand have a complete metamorphosis, with a quiescent pupal state, 

 in which the rudiments of the antenna?, wings, etc., are perceptible, and have the legs 

 arranged on the breast with the anterior pair directed forwards, a peculiarity not occurring 

 in any other insects. The mature female retains the beak, but does not acquire wings, 

 and the male has two wings, but the mouth parts disappear. 



The eggs are hatched beneath the protecting scale, which was formerly the mother's 

 body ; they soon make their escape, as active little six-footed grubs, with slender beaks 

 and two long bristles at the end of the body ; and in some species, as C. adonidum, the 

 Mealy Bug of the greenhouse, are covered with a white powdery covering. Most species, 

 however, are naked. At this stage both sexes are alike. 



As soon as they leave the scale they move along the branches towards the tip, and 

 fix their beaks in the bark of the twig. From this time they remain motionless, fastened 

 to the epidermis of the plant by means of small white downy threads emitted from the 

 undersides of their bodies, they lose the caudal bristles, a scale forms over them, and 

 they increase rapidly in size. 



