LACHNUS VIMINALIS. 67 



journeying is practised by the wingless individuals en 

 masse. Mr. James Salter observed that a large patch 

 of these insects had collected on the bark of a willow, 

 Salix daphnoides ; they appeared to screen them- 

 selves from the rough and rainy south-west wind then 

 blowing by retiring to the north-east side of the stem. 

 Four days later the same tree was visited by him, but 

 not a specimen could then be found by a most careful 

 search. On turning to another willow, Salix acumi- 

 nata, about five feet from the former tree, which 

 certainly was not infested four days before, the missing 

 patch was found. It is possible that this movement 

 was caused through their previous disturbance and 

 observation. If so, their march must have been very 

 persevering and determined, for the intervening 

 ground was covered by rank grass and weeds, ten or 

 twelve inches high. Cold November weather set in a 

 week later, and then not a single Aphis could be found 

 in places where previously, in another part of the 

 salictum, " myriads might have been collected without 

 difficulty." 



In Nottinghamshire this Aphis is sometimes very 

 common. Its visits are intermittent, but I learn 

 through a resident horticulturist that the harm they 

 do to the trees is not at all marked. Mr. Smee's 

 experience, however, would seem to be otherwise. 



Mr. Salter sent me in the following March some 

 thick willow stakes that had been infested durino- the 

 previous year. The effects of their puncturing was 

 conspicuous as brown stains disposed in stripes on the 

 grey bark. I could, however, discover no trace of 

 egg or hibernating female in the crevices, though 

 assisted by a lens. Whether the insect descends to 

 the earth for its winter shelter or not, is a question for 

 a future observer to settle. 



I believe that the Lachnus dentatus of Le Baron, 

 of America, is identical with Lachnus vimmalis, see 

 * Third Annual Report of Noxious Insects in Illinois,' 

 by Dr. Cyrus Thomas, 1879, p. 116. 



