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Explanation of figures—1, egg, scarcely one hundredth of an inch in length ; 2, young larva in 
its active 'stage ; 3, its appearance soon after becoming fixed ; 4, appearance of scale after the 
second plate is formed ; 5 and 6, insect at different stages, as seen under the scale ; 7, fully formed 
scale with inclosed insects, as seen from below : 8, antenna, highly magnified. The side figure 
shows the natural appearance of the scales on the tree. 
THE OYSTEK-SHELL BARK-LOUSE. 
(Mytilaspis conchiformis , Gmelin.) 
Order of HOMOPTERA. Family of Coccim®. 
Harris’s Treatise, page 252 ; Fitch’s 1st and 2d N. Y. Rep., p. 31; Walsh’s 1st Ill. 
Rep., p. 34; Riley’s 1st Mo. Rep., p. 7. 
The common Apple-tree Bark-louse, obscure and un¬ 
inviting as it at first sight appears, is, in many repects, 
one of the most anomalous and interesting* insects that 
comes under the cognizance of either the scientific or the 
practical entomologist. How it is propagated, how it 
obtains its nutriment, and how it migrates from one tree 
to another ; whether it flourishes best on a healthy or a 
debilitated tree, whether it exercises any selection 
amongst the different varieties of apple, and whether, 
with respect to its prevalence, it is upon the increase or 
fthe decrease, are questions which have long been in¬ 
volved in much obscurity, and some of which are yet 
I far from being satisfactorily solved. Yet it is an insect 
which has been long known, having been originally imported in¬ 
to this country from the other side of the Atlantic, and has been 
subjected to the prolonged scrutiny of some of the acutest ento¬ 
mologists that either Europe or this country has produced. 
It is one of the opprobria of entomology that the male of the 
Oyster-shell Bark-louse has never been discovered. Judging from 
the analogy of other species of the same genus, the male, if ever 
discovered, will be found to be a very small two-winged insect, 
yet having no special affinity with the dipterous order of insects. 
