474 



ME. H. IS^. RIDLEY ON THE 



very abundant and conspicuous Grecko with the Aniphishcsna, 

 which is often called the snake with two heads, or may have been 

 suggested by finding an accidentally fork-tailed lizard, of which 

 an example was obtained by our expedition. The " serpents " 

 were doubtless the AmpJiishcena. The large rats are much less 

 easy to explain ; at present the only rats occurring on the island 

 are Mus rattns, the coiiimou introduced black rat. It is impos- 

 sible that the animals seen by Vespucci could have been this 

 species, which could not at that time have been introduced. 

 It is possible that there was formerly an indigenous rat-like 

 mammal, which became exterminated by the black rat. We 

 could find no tradition even of this big rat, and I fear it is quite 

 extinct. The only hope of recovering its remains lies in an 

 examination of the guano deposits of Eat Island, where its 

 bones might be preserved. 



The number of insects belonging to the orders which are 

 well known as plant-fertilizers is surprisingly limited. A few 

 small species of moths haunted at niglit the bushes of Scoparia 

 dulcis, Cassias, &c. on the o^^en spaces. A single species of 

 butterfly was very abundant on Eat Island and the main island, 

 but we never saw it visiting flowers. 



The most important fertilizer was a small endemic hornet 

 belonging to the genus Polistes, wliich gathered honey from the 

 Leguminosse and Cucurbitacese ; and three small black species of 

 Halictus were caught in the flowers of the melons, Momordica 

 charanila, Oxalis Noronlice, and the mustard. The last plant 

 was also haunted by Temnoceras vesiculosus, a pollen-eating 

 Hyrphid. The only other insects which could also be considered 

 as possible fertilizers were Tachytes inconspicuus, n. sp.. and 

 Monedula signata, two sand-wasps, Fompilus nesophila, n. sp. 

 (Hymenoptera), and Psilopus metallifer (a Dipteron), but none 

 of these were seen at or near flowers. A small black beetle also 

 was found in the flowers of an Acacia in the Grovernor's garden. 



Though the number of species of insects was not large, 

 the individuals, especially of the Polisfes and ITalicfi, were very 

 numerous, but at the same time they seemed out of all propor- 

 tion to the immense number of flowers to be fertilized. It is 

 very probable, however, that the majority of the Leguminosse 

 and aome of the other plants were self-fertilized. 



The lake on the main island contained a species of Nitella and 

 an alga, an aquatic beetle and an Hemipteron, a new species of 



