DAMAGE CAUSED BY ANIMALS. 215 



so that they bend over where attacked near the middle of the 

 leaf. When these lice occur in large numbers, they make the 

 look as if besprinkled with snow. 



2. ON BROAD-LEAVED TREES. 

 Gall-midges (Cecidomyidse). 



The Beech Gall-midge, Cecidomyia (Hormomyia) fagi, is a small 

 insect of 016 to 0'2 inches in length, having a blackish-brown trunk 

 and flesh-coloured abdomen, and brownish wings with grey hairs, 

 which, during its larval stage, produces the hard, conical, pointed, 

 green and red galls often occurring in large numbers on the upper 

 side of Beech leaves. 



These midges swarm in April when the female pierces the 

 upper cuticle of the young Beech leaves, and lays an egg in each 

 wound, above which is formed the green cone containing the 

 maggot, or " strig " as it is called in many parts of England. 

 These excrescences gradually change to a deep red colour, and 

 about October drop off to the ground. Very early in the follow- 

 ing year the chrysalis is formed inside the gall lying on the ground, 

 when the imago emerges in April to repeat the cycle of reproduction. 1 



Gall-wasps or Gall-flies (Cynipidse)? 



Most of the Gall- wasps attack the Oak, on which about 50 

 different species are known. 



1 Two closely related species, the, Willow or Osier Gall-midges, Cecidomyia solids 

 et C. saliciperda, also deserve a passing glance. The former is a small, blackish, long- 

 legged midge, 0*12 to 0*14 inches long, whose abdomen is ringed with red, and has 

 whitish hairs. The ova are deposited on young shoots (principally on Salix purpurea) 

 in May, and again in July. Through their suction the reddish -yellow maggots or 

 strigs occasion spindle-shaped swellings which render the withes useless. From 

 May onwards, twigs infested should be cut off and burned. The other species, 

 C. saliciperda, is still smaller, being only '08 to '12 inches in length, with blackish- 

 brown body, and milk-white wings. During May the ova are deposited in a long 

 string on the back of young shoots and stems of Willows (chiefly on Salix alba, S. 

 mminalis, and S. acutifolia), and in June the reddish-yellow maggots work their way 

 into the inside, where, from July till the following April, they bore irregular vertical 

 galleries, at the same time causing the formation of spindle-shaped swellings, which 

 ultimately become scabby from the bursting of the bark, and within which the chry- 

 salis remains. When it is not convenient to cut out the shoots or stems infested, 

 the swellings should be smeared with patent tar. (Hess, op. tit,, vol. ii. p. 98). 

 Trans. 



2 The Gall-wasps or Cynipidx are, among insects, one of the most interesting 

 families, for, like a good many fungi, they have the peculiarity of possessing an 



