ON THE ENGLISH SPECIES OF RED SPIDER. 49 



4. Revision of the English Species of Red Spider (Geneni 

 Tetranijchus and Oligonyclms). By Stanley Hirst. 



(Published by permission of the Trustees of the British Museum.) 



[Received December 8, 1919 : Read February 24, 1920.] 



(Text-figures 1-5.) 



The following note deals with the English species of mites 

 commonly called Red Spiders, and is almost entirely based on 

 material collected by the author, the coloration being described 

 from living specimens. A good deal of confusion still exists in 

 the classification of this group — for instance, the name Telra- 

 nychus telarius is not always used for the same species by recent 

 authors, and several distinct species {2\ tiliariimi, T. lintearius, 

 T. 2>opultj and Oligonychus quercinus) are wrongly considered as 

 synonyms of that species. Three new species are described in 

 tlie present note, but one of them {T. talisice) is undoubtedly an 

 introduced form. 



My best thanks are due to Lieut. -Col. Sir David Prain (Kew 

 Gardens), Prof. W. Bateson (John Innes Horticultui^al Station, 

 Merton), and to the authorities of the Royal Horticultural 

 Society's Gardens, Regent's Park, for kindly allowing me to 

 collect material in the gardens under their chai'ge. 



The drawings illustrating this note have been made by Mr. Pei'cy 

 Highley and Mr. A. J. Engel Terzi. 



Order PROSTIGMATA. 



Superfamily Tromhidloidea. 



Family Tetranychidje. 



The two principal genera Tetranychus and Oligonychus can 

 be readily distinguished from one another by the following 

 characteristics : — 



Claw of legs always simple and unmodified (never bifurcated nor 

 furnished with teeth) ; it has a slight protulaerance near the base 

 beari ng minute hairs Genus Oligonychus Berlese. 



First claw of niale either ending in minute teeth or bifurcated. Claw 

 of the other legs in both sexes usually either ending in fine hairs or 

 bifurcated Genus Tetrani/chus Dufour. 



Genus Tetranychus Dufour, 1832. 



Key to the species of Tetranychus (males) occurring in 

 England : — 



fTerminal finger of palp minute and inconspicuous or 



\ 



ibsent 1. 



l^Terminal finger well developed 4. 



fTerminal finger of palp absent. 



1 All the claws of the legs bifurcated Tetranychus schizopus 



[Zaclier. 

 Terminal finger present, but minute. 

 [^Claw of first leg alone bifurcated 2. 



Proc. Zool. Soc— 1920, No. IV. 4 



•1 



