110 OUTLINES OF ENTOMOLOGY. 4 



eggs begin to form and soon fill the body of the mother insect. Upon 

 hatching, the very minute lice creep from under the scale and disperse 

 with great activity all over the tree or branch, from whence some are 

 carried by birds and insects, or are wafted by the wind to other trees, 

 and in this way they are disseminated from one orchard or vineyard 

 or grove to another. Besides the waxy scale, some species excrete a 

 great quantity of white, cottony matter, as a protection to the eggs. 

 This substance is arranged in various forms characteristic of the spe- 

 cies. 



Among the coccids that form simple scales is the widely-distributed 

 Oyster-shell Bark-louse of the apple (Mytilaspis pomonum, Bouche.) 

 This species covers the branches and trunks of trees with its pale 

 brown, somewhat oyster-shaped scales, beneath which are the females, 

 each with its almost invisible beak penetrating to the growing wood 

 and extracting sap in such quantities as to retard the growth of the 

 tree, and reduce the quantity and impair the quality of the fruit. 

 The young are hatched late in spring, and are active for a few days 

 only. Alkaline washes or kerosene emulsion applied at this time are 

 most effectual in preventing their increase. They have a few natural 

 enemies in the shape of Coccinelid beetles, Lace- wing fly larvae and one 

 or two minute parasitic flies. Two similar scales of other species are 

 found in the South on orange trees. Several species of white scales 

 (ChionaspisjaTQ also found on apple, pear, pine and willow. A smaller, 

 white, scurfy scale (Diaspis) is sometimes very abundant on the stems 

 of roses, blackberries and raspberries. The scale insects most trouble- 

 some in green-houses and on house-plants, and occurring also on the 

 orange, belong to the genus Aspidiotus. Among the scale insects that 

 produce cottony masses is Pulvinaria innumerabalis (Rath.), which ap- 

 pears in great numbers on grape vines, and especially on maple and 

 elm trees, covering the bark with its masses of flocculent matter and 

 honey-dew like excretions, greatly disfiguring and injuring vines and 

 trees. The orange tree is especially subject to the attacks of scale 

 insects; and one of these, the Fluted scale f leery a purchasij, seriously 

 threatened the existence of the groves of California, until Dr. Riley 

 happily discovered its chief natural enemy in Australia, from which 

 country the scale had been introduced, and secured the importation of 

 the useful Lady-bird beetle, which in about two years has almost exter- 

 minated the particular species of pest on which it naturally preys. 



The Mealy bugs (Dactylopius) especially troublesome on house- 

 plants and in green-houseswhile agreeing with the scale insects in 

 many particulars, do not secrete scales and the females do not become 

 fixed in one place. The bodies are covered with a white powdery 



