SPINNING MITES. 103 



CASE Tetranychus ferrugineus {Boisd.), Ent. Hort., p. 90. 

 VIII. 



This mite lives in greenhouses on the Cyclamen Coum and 

 persicum, and often makes great ravages. It pricks the leaves 

 underneath, beginning at the base of the petioles. When these 

 are attacked by the little insect they take a violaceous or reddish 

 hue above ; their vegetation is stopped, they fade and fall. In 

 examining them with the glass, the underside is seen to be 

 covered with small blackish dots caused by the prickings of this 

 microscopic parasite. It is excessively small, of a more or less 

 dark ferruginous red. When the cyclamen begins to be attacked, 

 which can be seen at the first glance, the only remedy, according 

 to M. Boisduval, is to Hft the pots and burn the tubers in order to 

 prevent these little beings spreading over the neighbouring plants. 

 Flower of sulphur has been tried as a remedy with Httle success. 



Tetranychus russulus {Boisd.), Ent. Hort., p. 89. 



This is a little mite mentioned by M. Boisduval, which he thinks 

 has probably been imported from Mexico, or from some other 

 country of Central America. It is only found on cacti, particu- 

 larly on the mamillaria, the echinocactus and neighbouring kinds, 

 and is known to amateurs of succulent plants under the name of 

 ro2igct. It is ferruginous red and almost microscopic, and does 

 much damage to the plants on which it estabHshes itself, and if 

 remedies are not promptly applied, it soon destroys them. 



Fumigations of tobacco, or powdering the plants with it, have 

 been used in such cases with success. 



Tetranychus vitis {Boisd.), Ent. Hort., p. 92. 



M. Boisduval gives the following description of this species : — 

 *' When towards the end of summer we see the leaves of the 

 vine marbled above with broad yellow blotches, it is often the 

 indication of the presence of a very small parasite, which lives in 

 family on its under side. On examining such a leaf with a very 

 powerful lens, we see at first that it is carpeted with a rather loose 



