31 [451] 



Dr. Fitch lias given an account of this insect in his second ISTew York 

 Eeport, and points out the principal varieties, but without referring 

 them to their corresponding larvie. 



We have spoken above of the comparatively late season of the year 

 when the Datana-moths issue from the pupa state in which they have 

 passed the winter. This circumstance might suggest an interesting in- 

 quiry into the causes which produce the great diversity in the periods 

 of insect life. Not only do animal, as well as vegetable organisms oc- 

 cupy every part of nature's domain, but they are also widely distributed 

 as respects the seasons of the year. As we have our spring, summer, 

 aud fall flowers, so we have our early and late insects, destined to keep 

 in check the earlier and later vegetation. One way in which this is 

 brought about is an unexplained diflfereuce in the time required for the 

 develoj^^ment of different species of insects in the i)upa state. Of the 

 many moths which pass the winter in this condition, some emerge in the 

 month of May, a much larger number in June, whilst a few, like the 

 moth of the fall web-worm, and the Datana minutra of which we have 

 here been treatiug, often lie dormant till well into July. The ultimate 

 or economical reason for this diversity is sufficiently obvious, but the 

 actual or physiological causes which produce it, are' unknown, and j)er- 

 haps unknowable. All we can say is, that it is their nature to do so. 

 Here, for instance, are two chrysalids, lying side by side, belonging it 

 may be to closely allied species, and scarcely distinguishable from each 

 other. Yet one shall feel the first touch of sping and come forth, whilst 

 the other shall lie dormant and motionless, heedless alike of winter's cqld 

 and summer's heat, till at length the dial points to the predestined hour 

 in the cycle of its existance. Then, without any known or visible cause, 

 the vital forces begin to circulate, and the creature exhibits tokens of 

 reviving animation, within the darkened chamber of its sepulture. 

 Gradually it rouses itself from its lethargy, and throws off its swaddling 

 cerements, and puts on its beautiful garments, and comes forth to the 

 light and liberty of a more exalted state of existance. 



We do not mean to say that these changes take place without the op- 

 eration of natural causes, but that these agencies are of so subtile a na- 

 ture, and of so delicate an adjustment, that they will probablj^ forever 

 lie beyond the reach of human investigation. 



PRACTICAL TREATMENT. 



This insect has never been known to increase to any very serious ex-' 

 tent, an€l it cannot be regarded, at most, as more than a third-rate inju- 

 rious insect. We have occasionally seen small apple trees nearly defo- 

 liated by them ; but our own experience has been mostly with the black 

 walnut variety. We have an ornamental row of these trees which we 



