278 



Marvels of Insect Life. 



Pliolo by 



A Common Scale-Insect. 



organs except the rostrum, 

 which still enables them to 

 feed. The eggs are deposited 

 under the scale, from which 

 the young grubs emerge after 

 a short period of crowding 

 together. Then they disperse 

 and seek unoccupied spots 

 in which to thrust in the 

 rostrum and become fixed. 



The scale- Insects are not 

 a large famil}'. Only about 

 eight hundred species are 

 known from all parts of the 

 world, and less than a hundred 

 of these have been found in 

 the British Isles, of which 

 number a very few are real 

 natives, most of them having 

 found their way into green- 

 houses with foreign plants. 

 It is here that the scale- 

 out of doors it is doubtful if 



On tho stems of wild rose and dogwood often may be found what look like little 

 drops of fat or wax. Examined under the microscope, it will be seen that the 

 pointed end consists of a female scale-Insect, and the broad, fatdike expansion is 

 a marginal secretion of wax. The photograph shows a portion of a colony of 

 adult females on dogwood, and is magnified twelve times. 



Insects are chiefly a terror to the gardener ; 

 much damage is done in our climate, the most serious pests in this department 

 being the mussel scale ^ and oyster-shell scale,- which attack fruit trees. In the 

 greenhouse, where they have to deal with more tender plants, and are actively 

 sucking at the sap all the year round, the damage they inflict often amounts to 

 extirpation of the plants. The sucking at the juice is not the only trouble. Scale- 

 Insects, like green-fly, excrete a sweet, clear liquid, which is eagerly sought by ants, 



bees, wasps, and other Insects, 

 and as some species that have 

 been watched have been found 

 to discharge this liquid twenty 

 times in a day, it will be seen 

 that a considerable quantity 

 accumulates on the leaves of 

 greenhouse plants, where 

 heavy showers cannot wash 

 it away, as they do outside. 

 This sticky coating on the 

 leaves provides a suitable 

 medium for the development 

 of a low form of fungus, which 

 runs riot in it. This fungus 

 does not attack the tissues of 



A.spidiotiis ostreaefonnis. 



Photo by] 



A Common Scale-Insect. 



[W. West^ 



A single example from the group in the preceding photograph is here shown on a 

 larger scale ; that is, twenty-five times the natural size. The dark mark in the 

 broad margin is a juvenile example of the same species. 



^ Mytilaspis pomorum. 



