290 JOUKNAL OF THE ROYAL HORTICULTURAL SOCIETY. 
can attach themselves very firmly to an object, and moreover that their 
strength must be comparatively great. 
The epidermis or skin, like that of true insects, is composed of chitine, 
and, although apparently so delicate, will resist the action of a 10 per cent, 
solution of boiling caustic potash for several minutes, and it takes from 
10 to 20 seconds' exposure 6 inches from a good coal fire to destroy its form. 
The actual length of a single mite is about -20 -'23 mm., which 
means that it would take about 120 of them placed end to end to make a 
lineal inch. 
This species of mite is not a true insect, but belongs to the order 
Acarina, which includes in it the red spiders and cheese mites, the parasitic 
mites of the mammalia, wild bees, and beetles, &c., but is distinguishable 
from all these, both in the immature or nymphal forms and in the adults, 
by the elongate form of the body and the possession of only two pairs 
of legs, and as such constitute the family Phytoptidae. Several species 
Fig. 160. — Venteal View of Phytoptus Fig. 160a. — Head of the Same, 
ribis X 350. more highly magnified. 
of the family are met with in this country ; those most familiar to the 
horticulturist being the Hazel gall-mite {Phytoptus avellanm) and the 
Pear-leaf blister-mite (P. jpyri). The Lime and certain species of Acer and 
the common Yew have also species peculiar to them ; but all these, as is 
generally known, do not confine their attacks to the buds as in the case 
of P. rihis. 
Habits and Life History. — The following observations made during 
every month of the year are the result of constant and repeated examina- 
