84 



TFIE ENTOMOLOGIST. 



loosely imbricated irregiilav scales (as shown magnified, fig. 1), 

 from the natural growths, which are smooth and lanceolate in 

 general outline. A few months later (about the beginning of 

 February) a touch to one of these distorted buds will often 

 throw off" all the diseased scales, and at their bases the 

 coming growth will be found in the numerous minute round 

 buds set close together on the common thickened centre, as 

 shown, magnified, at fig. 2. The growth of the knot from 

 these embryo buds is the work of years; but whilst the tree 

 is still bare of leaves it may be found in every stage of 

 progress: the shortened shoot beset with swollen buds, as 

 (magnified) at fig. 3; the compound form, where many buds 

 have grown close together so as to present a hard cluster, 



nq.i 



with a few shoots starting from it, fig. 4 ; and so onwards, till 

 the witch-knot is fully formed, a mass sometimes more than 

 a yard in diameter. 



The Phytoptus causing the diseased growth is grayish 

 white, cylindrical, and rarely exceeding one two-hundredth 

 of an inch in length, and a quarter of that measure at its 

 greatest width ; but its powers of elongation and contraction 

 make it difficult to give more than an approximate measure- 

 ment. From the insertion of the legs to the caudal foot the 

 Phytoptus is marked with transverse strise of such minuteness 

 as to give about a hundred to the length of the body, these in 

 the early life of the gall-mite being deeply corrugated; when 

 full grown the bands are marked with dots, about thirty-two 

 to the circumference of the mite, having a projection, when 

 seen against the light, as if possibly composed of a pencil of 

 short hairs. The legs, at full stretch, only extend about half 

 their length beyond the head, and when in motion the 



