366 ARACHNOIDEA. 



CASE buds of the alder unfold, one can see on the still tender leaves 

 already the beginning of these Cephaloneons. It shows as a 

 small round yellow little spot, which has in the middle a green 

 point. On every such spot a gall developes itself in a short time, 

 so that by the middle of May it is already one millimetre in size 

 in which at that time is to be found two to four brownish white 

 Phytopti, J of a millimetre in length. 



Phytoptus Sp. 



This species produces bHsters of the upper side of the leaf, in 

 the angles of the nerves on both sides of the middle nerve, 

 harbouring a pale honey-coloured cylindrical mite, i of a milli- 

 metre in length. 



It frequently happens that the three above-mentioned mite 

 galls are found on one and the same leaf. Besides these there 

 is : — 



Phyllerium alnigenum, Lnk. 



On the under side of the leaf of Alnus incana. 



On the Birch Tree 

 Erineum betulinum, ScJmnu 

 Very short, spherical, and thickened at the end, like white trans- 

 parent pegs placed here and there over the surface of the leaves 

 and leaf-stalk, which appears, to the naked eye, to be strewn over 

 with fine white morsels of quartz. The Phytoptus belonging to 

 it is one-sixth of a millimetre long, and transparent white. 



On the Hornbeam. 



Phytoptus Sp. 



This species forms crumpled foldings of the ribs of the under 



side of the leaf, which, according to Frauenfeld, contain no hairy 



formation. In May a yellowish Phytoptus is to be found in 



them scarcely one-eighth of a millimetre in length, with two com ■ 



