DISTRIBUTION OF INSECTS. 



279 



sionally seen # . Mr. Darwin has recorded (Nat. Voy. p. 587) 

 that "a few grasshoppers occur a little inland at Ascension," and 

 that " rats and land- crabs swarm in numbers." The island bears 

 all the marks of having been the seat of volcanic action at a 

 comparatively recent time ; and the poverty of its fauna and flora 

 may very probably be due to the shortness of the period during 

 which it has been in a condition fit for the reception and support 

 of organic life, as well as to its very restricted area. Sea-birds are 

 very numerous, and some of them, I was told, nest on the island. 

 The marine fauna, from the little that I could observe of it, struck 

 me as one that would repay a systematic research. I believe 

 that both the mollusks mentioned by Mr. Murray (p. 15), cer- 

 tainly the Nerita, were among those which I found crawling in 

 abundance on the rough tufa-rocks near the turtle-ponds, and 

 subsequently presented to the British Museum. A bivalve, which 

 appeared to be a true oyster, was plentiful just about the water- 

 line ; and numerous shells of other mollusca, bleached to whiteness, 

 lay in the rock crevices ; while the general abundance of that 

 class of animals was amply evidenced by the long beach of the 

 well-known " Ascension sand," which appeared to consist solely 

 of rolled and polished fragments of shells. Several splendidly 

 coloured fish, resembling Acanthurus, were taken by the hook 

 over the side of the steamer at her anchorage ; and many others 

 could be discerned in the clear water near the shore, as well as 

 companies of gaily striped and spotted small species in the turtle - 

 ponds. But the most striking and active animal I noticed was 

 a species of crab (of the genus Ocypoda ?) which swarmed on the 

 hot rocks, close to the sea, in the full sunshine. These crabs 

 possess an amazing agility, reminding one in their actions of the 

 quickest hunting spiders, and evade with remarkable success any 

 attempt to seize them ; I even found it difficult to strike them 

 with a stick. Their colouring is protective, being a dark reddish- 

 purple, thickly spotted with white, and nearly resembling that 

 of the rocks which they frequent, the spots representing the 

 numerous orifices in the porous tufa. 



In reference to St. Helena, Mr. Murray observes (p. 22) : 



* I remember to hare read, in an account of a visit to Green Mountain (upon 

 which I cannot now lay my hand), that variegated reddish butterflies were ob- 

 served on the ascent. In all probability these were Pyrameis Cardui. Green 

 Mountain has on it a scanty native vegetation, as well as introduced vegetables 

 and garden-flowers. 



