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; SCALES IN MINNESOTA. 461 
sacks capable only of feeding and secreting the scale. The mouth 
of a scale-insect consists apparently of a very long, slender and 
thread-like sucking-tube, which is thrust into the tissue of a plant, 
serving as a sort of hose through which the sap ascends. To secrete 
the scale the insect is provided with many spinnerets at the poste- 
rior end of the abdomen. The arrangement of such spinnerets, or 
spinning-tubes, is very constant in the different species, and is made 
use of in classifying the numerous species of scale insects. These 
spinnerets are not easily seen, not even with a microscope, and to 
make them atall clearisa difficult matter, as the insect has to be 
boiled for many hours in a strong solution of caustic potash, so as 
to remove all the soluable matter in and about the spinnerets. 
In due time the male insect molts for the second time and changes 
to the pupal state, in which the wings, feelers, legs and other 
appendages are formed inside the pupal skin. Before long the 
male emerges asa very delicate, two-winged insect, with peculiar 
hooks in place of the lower wings, destined to strengthen the upper 
ones during flight, and with one or twolong and tail-like append- 
ages. The male, living but avery short time, requires no food and 
consequently its mouth has become rudimentary and is frequently 
replaced by a second pair of eyes. 
The female bark-louse always remains under the scale; she stays 
at home and is evidently nota believer in woman’s rights. Soon 
after the union of the two sexes the male dies, and the female com- 
mences to deposit eggs, retiring into one end of the scale, and 
gradually shrinks during the process to a mere shriveled skin, as 
indicated in the illustration showing the Oyster-shell Bark-louse. 
In some cases no eggs are deposited, but the female gives forth 
living young, as is the case in the related family of leaf-lice or 
aphids. 
‘The time in which eggs are laid varies with the species, many 
depositing them during autumn, but most species, passing the 
winter in a not fully grown condition, deposit them in the spring. 
The forms of the scales vary considerably, and most of them have 
such a characteristic appearance that they can be readily recognized 
by the naked eye. Others, however, can only be distinguished by a 
very careful investigation. 
As these insects travel only in their larval state, they can not 
readily reach plants, only a few feetaway. In this respect they are 
not nearly as well equipped as the leaf-lice, or aphids, where winged 
forms appear from time to time to enable the members of too 
crowded colonies to search and find new feeding grounds. Young 
scale-insects are often carried upon the feet of birds to distant 
places, starting new colonies in case the latter alight on plants of 
the proper kind. This explains the fact why scale-insects are so 
frequently found near the nests of birds. Other insects also carry 
them, especially the almost omnipresent ants, who are apt to spread 
them from tree to tree, so that an orchard will be soon invaded in 
all directions. The wind may also blow the young larve from plant 
to plant. But man is the main cause of scattering these injurious 
insects from place to place, from country to country, and not too 
