THE ENEMIES OF ENGLISH WOODLANDS 285 



which often tear up considerable areas of grass in order to 

 reach the fleshy grubs lying below, while moles also destroy 

 large numbers. 



The Lakch Aphis. 



This aphis is sufficiently plentiful, and its presence is 

 so conspicuous, that the most careless observer can hardly 

 avoid noticing it on young larch plantations. Foresters 

 who have assisted in thinning young larch have more or 

 less vivid recollections of its unpleasantly sticky nature, due 

 to the resinous matter in which the insects are enveloped. 

 The life-history of the aphis is comparatively complicated, 

 having what is known as an alternation of generations. 

 The mother aphis, which has hibernated in the axil of a 

 leaf-bud or a crack in the young bark, wakens up from 

 her dormant condition in April, just as the short spurs of 

 the larch are breaking into leaf. Her one and only duty 

 consists in egg-laying, from twenty to forty eggs being laid 

 in a cluster on the spot she has lain on since the previous 

 autumn, after which she dies. These eggs hatch out in a 

 week or ten days, and the larvse at once proceed to infest 

 the young larch needles, from which they derive their 

 nourishment by piercing the soft tissues of the needle 

 and feeding on the sap. These develop into winged or 

 wingless aphides, and successive generations are produced 

 at intervals of about six weeks until autumn, when the 

 last laid eggs are said to produce the mother chermes, 

 which is destined to carry on the swarms of the following 

 year. 



It has been asserted that the larch aphis and the spruce- 

 gall aphis are alternate generations of one and the same 

 species. Whether this is so or not we are unable to say 

 from personal observation. We have seen winged aphides 

 on spruce shoots while the larvse in the galls were still 

 young and immature at the end of May, but whether they 

 were connected with those in the neighbouring larch we do 

 not pretend to say. 



In ordinary plantations, attacks of larch aphis must be 



