OF ARTS AND SCIEXCES. 39 



currents of streams ; but every careful obser\^er knows that, with 

 the potency of these agencies admitted, much remains to be ex- 

 plained ; as, for example, wh}^ certain species appear to be defi- 

 nitely restricted to certain stations within a given area. Nan- 

 nothemis bella affords a striking example for the territory about 

 Manchester. This little Dragonfly is active, is a fairly strong 

 flyer, and remains with us in the imago stage nearly two months 

 — from the middle of June through Julj^ and into the beginning 

 of August ; and yet somewhat careful collecting in the vicinity 

 of Manchester has failed to discover Nannothemis bella in more 

 than one station. There individuals are numerous. The pools 

 on the right of the road leading to Goff's Falls, near Pine Grove, 

 are fed by cool springs which, it is believed, never fail. Thej^ 

 certainly withstood the severe drought of last j^ear. The water 

 in this chain of pools is clear, but the bottom is entirel}- covered 

 with a rich growth of sphagnum. Here Nannothemis bella has 

 escaped the test of drought, and is it not at least possible that, 

 lacking the capacity for survival inponds whose margins might 

 in any year be changed to mere mud-beds, this species long ago, 

 after mau}^ fruitless trials at distribution hereabouts, found itself 

 restricted to the single station where it is now found ? 



But if this theor}' of tropical hibernation during the dr}- sea- 

 son appears somewhat fanciful when applied to New England 

 Dragonflies, we may return to the brook on Sm^-th Road, and 

 to a simple statement of facts. Last Juh' this rivulet, along 

 which, in ordinar}' 3'ears, the late-flying species of Dragonflies 

 are abundant, shrank, first to mere puddles, and at last to an 

 empt}^ channel, seemingh^ as dr}- as empt3^ But the little stream 

 has overhanging banks, a common characteristic of New Eng- 

 land brooks when flowing through deep meadow land, and un- 

 der these banks, in several reaches of considerable extent, the 

 mud remained moist thioughout the drought. A small number 

 of living Dragonfly nymphs were found here on the occasion of 

 several visits, and some of them undoubtedly survived . the 

 drouth, to emerge as the imagos obsen^ed here in September, 

 going as contentedh- about their aflairs as if thousands of their 

 companions had not perished — an example of the survival of the 



