INSECTS AND VERMES. 469 



EPHEMERA CAUDA TRISETA MAY FLY. 



JUNE 10, 1771. Myriads of May flies appear for the 

 first time on the Alresford stream. The air was crowded 

 with them, and the surface of the water covered. Large 

 trouts sucked them in as they lay struggling on the 



descriptions, that Markwick may have correctly indicated the insect ob- 

 served by White : for I am not aware that the caterpillar of any small moth, 

 except the Tortrix viridana, denudes the oak of its foliage to so great an 

 extent as that noticed in the text. White's insect evidently belonged to 

 the family of TortricidcE, or leaf-rollers, as they may be called ; as is shown 

 by its pupa being wrapped up in a leaf, which was rolled round it, and 

 secured at the ends by a web to prevent it from falling out It conse- 

 quently could not have been the Phalama Querc&s, LINN., a large moth 

 belonging to the Bombycida, the pupa of which is enveloped in a cocoon 

 of considerable size, as is seen in that of the silk-worm, perhaps the most 

 familiar instance of the family. The Phalcena quercana is a leaf-roller : 

 but this could scarcely have been White's moth, as its deep rufous-yellow 

 wings would not have appeared to him of a pale yellow colour ; and I 

 have besides no reason for believing that it ever abounds on the oak so 

 excessively as to strip the trees of their leaves. The latter remark would 

 also apply to the Tortrices of the genus Dictyopteryx of Mr. Stephens ; 

 some one of which may, however, possibly have been the insect meant. 

 But great ravages are unquestionably committed by the moth described 

 by Markwick, known to aurelians by the name of the pea-green. Ha- 

 worth's remarks on it, in his Lepidoptera Britannica, are confirmatory of 

 Markwick's observations, and are worthy of perusal, not merely on that 

 account, but as they include also an exposition of one of those admirable 

 provisions of nature by which excess in any single department is coun- 

 teracted. 



" In most seasons," Mr. Haworth says, " this insect occurs in greater 

 abundance than any other of the genus ; but a few summers since they 

 were produced in such amazing quantities about London, and also in 

 Norfolk, as threatened annihilation to our oaks; and must eventually 

 have really destroyed them, had not nature, by one of her admirable 

 efforts, cured the calamity in her own way : by simply starving the Tor- 

 trices. The oaks were defoliated by their voracious larvae ; not a perfect 

 leaf, nay hardly the rib of one, was left; in consequence of which myriads 

 of the caterpillars perished through want and hunger, or failed, through 

 weakness, to surmount the difficulties of pupation. So that very few 

 eggs were deposited for the following season ; which, as I predicted, 

 was not overburthened with an increase of the Tortrix, as many expected, 

 and which would have ruined the oaks : but, with such an astonishing 

 diminution, that hardly a single specimen was to be found where, but the 

 year before, thousands swarmed on every oak." E. T. B. 



