HAZEL AND FILBERT BUD MITE. 115 



Phytoptus which causes it and also in that of the abortive, 

 swollen, and mite-infested buds to that of P. ribis, figured at 

 p. 60, that it is unnecessary to give a sjDecial illustration. 

 Like it, the mite is too small to be distinguished by the naked 

 eye. The life-history of the two sj^ecies is similar. 



It belongs to the great order of Acarina, but, together with 

 the others of the genus Phytoptus, is distinguishable by its 

 cylindrical shape gradually lessening towards the tail ex- 

 tremity ; and also by only possessing throughout its life, from 

 the time of hatching from the egg, two pairs of legs placed 

 near the head extremity behind the somewhat conical-shaped 

 feeding-apparatus. The above peculiarities distinguish the 

 genus Phytoptus clearly from others of the Acarina, of which 

 the Ked Spider of the Hop may be taken as an example, 

 which have a more or less oval or rounded shape, and, as a 

 rule, four pairs of legs during all their life, excepting in the 

 earliest stages, when they have three pairs. 



The shape of the female and larva is cylindrical ; that of 

 the males, when arrived at the stage of sexual development, 

 not unfrequently spindle-shaped. The length of the female 

 may be as much as twenty-one hundredths of a millimetre 

 (0"21 mm.) ; of the male eighteen hundredths (0*18 mm.) ; the 

 breadth from four hundredths of a millimetre to much less 

 (0'04-0"065 mm.) ; and a millimetre being a twenty-fifth part 

 of an inch, it is commonly more by the characteristic deformed 

 growth of the buds than by identification of the species of the 

 mites that the attack is known. 



As in the case of the Black Currant infestation the develop- 

 ment of the bud lengthways is checked, and it forms a more 

 widened spherical growth, with an abnormal number of bud 

 scales and abortive leaves ; these, consequently on the ab- 

 normal development of the cellular tissue, are thickened and 

 more or less sprinkled with hairs or other excrescences. 

 These deformed buds may be found early in the spring, even 

 before the Hazel leaves show themselves, and at this time the 

 leaves, or scales of the buds, are already for the most part 

 plentifully sprinkled with Phytoptus eggs. Later on the buds 

 dry up, and fall, having been previously deserted by the Gall 

 Mites, which are now mostly to be found in the newly formed 

 leaf-buds. 



With the second growth of the shoots of the Nut bushes in 

 July and August, a second growth of deformed buds is again 

 observable, distinguishable by their remarkable size and green 

 colour. 



This infestation has been so rarely reported that I have 

 had little opportunity of studying it myself, and the above 

 observations are chiefly taken from those of Dr. A. Nalepa, 



I 2 



