BEETLE MITES. 213 



CASE the shelter of mosses is what they prefer, and it is there that they 



XIII. r ^ - , 



are found m greatest number. 



According to Curtis again, whose statement we can confirm 

 from personal observation, at all events the commonest and most 

 typical species of them, Damreus geniculatus, is found chiefly 

 under bark, and specially under the bark of fruit trees, and, 

 instead of being solitary and vagabond, it is gregarious, and con- 

 gregates in the spring in great numbers at the base of the twigs, 

 so much so, as to look like a gummy exudation. Mr. Curtis, in 

 consequence of their prodigious numbers, thinks that by extract- 

 ing the sap they must weaken the trees, and in all probability 

 reduce the size of the fruit. But M. Boisduval has been able to 

 show authoritatively that this idea is erroneous. He says : — 



"In 1858, M. Riviere brought here a great number of indi- 

 viduals of the Oribates geniculata (the black stone tick of Geoffrey), 

 which had multiplied in a prodigious manner in the hothouse of 

 the old garden of the School of Medicine, to such a degree that 

 several orchids were covered by them. This clever observer was 

 rather alarmed at the sudden apparition of all these ticks on a 

 family of plants which he particularly affected ; but he was soon 

 re-assured when he saw that not a single leaf had suffered the 

 slightest alteration, and that these little animals were hunting 

 acarus, thrips, etc., of which they were eating the eggs and larvae. 

 At the end of some months all had disappeared. From whence 

 came this legion of Oribates ? He thinks that the eggs, or indi- 

 viduals recently hatched, had been brought in the moss and 

 sphagnum of which horticulturists make use for the culture of 

 exotic orchids, and that the development had taken place m 

 the panniers and baskets containing these plants. The horti- 

 culturist is therefore to regard them as friends and not as 

 enemies. 



The more important characters used in subdividing the species 

 of this group, are drawn from the number of claws to the tarsi, 

 and certain peculiar plates or expansions, which are borne by 



