and Systematic Arrangement of British Spiders. 45 1 



the genus Thomisus, it has the power of changing the colour of 

 the anterior intermediate pair of ej'es from dark red-brown to 

 pale golden yellow by a very perceptible internal motion. No 

 such motion appears to occur in the other eyes, which are always 

 black, 



39. Tliomisus trux. 



Thomisus trux, Blackw. Ann. and Mag. Nat. Hist. vol. xviii. p. 300. 



An adult male of this species was taken among grass in a 

 pasture at Oakland in June 1846, and I have since met with 

 several individuals of the same sex running on the ground in 

 fields near Llanrwst. 



40. Thomisus incertus. 



Thomisus iwcer^M*, Blackw. Ann. and Mag. Nat. Hist. vol. xviii. p. 297. 



My son, John Blackwall, discovei*ed a specimen of this spider 

 in an outbuilding at Oakland in June 1845 ; it was a male with 

 the palpal organs fully developed, and in the spring of 1850 I 

 received an adult female from Miss Ellen Clayton, who captured 

 it in Dorsetshire. Tliomisus incertus appears to be nearly allied 

 to the Xysticfus praticola of M. Koch (Die Arachn. B. iv. p. 77. 

 tab. 130. fig. 300, 301). 



41. Thomisus citreus. 



Thomisus citreus, Walck. Hist. Nat. des Insect. Apt. t. i. p. 526 ; 



Latr. Gen. Crust, et Insect, torn. i. p. 1 1 1 ; Hahn, Die Arachn. 



B. i. p. 42. tab. 11. fig. 32 ; Sund. Vet. Acad. Handl. 1832, 



p. 219; Blackw. Linn. Trans, vol. xix. p. 122. 



datici, Hahn, Die Arachn. B. i. p. 33. tab. 9. fig. 27. 



calycinus, Koch, Die Arachn. B. iv. p. .53. tab. 124. fig. 283, 



284 ; Uebers. des Arachn. Syst. erstes Heft, p. 24. 



Flowers growing in fields and gardens are the favourite resorts 

 of Thomisus citreus, which occurs in various parts of England and 

 Wales. There is great dissimilarity in size and colour between 

 the sexes; so much, indeed, that they have been described as 

 difi"erent species. 



Genus Philodromus, Walck. 



43. Philodromus dispar. 



Philodromus dispar, Walck. Hist. Nat. des Insect. Apt. t. i. p. 553 j 



Blackw. Linn. Trans, vol. xix. p. 123. 



fallax, Sund. Vet. Acad. Handl. 1832, p. 226. 



limbatus, Koch, Die Arachn. B. xii. p. 85. tab. 416. fig. 1017, 



1018. 



This active spider frequents wooded districts in England and 



29* 



