424 PERCY SLADEN TRUST EXPEDITION 



mentioned that the majority of the insects belong either to Madagascar or East African 

 forms, this being especially the case with the Lepidoptera. Dr Neils Holmgren, however, 

 records the three species of termites obtained as belonging to East Indian forms (though 

 two of the species are new). When it is remembered that termites are distributed by the 

 sea on floating logs and that the current runs from east to west, this result is precisely the 

 one which would be expected. In general it is probable that those insects which are 

 distributed by flying will on Aldabra belong to Madagascar or African forms, while on the 

 other hand those that are sea-distributed will be Oriental in origin. 



If) Myriapoda. One small species was very common among dead leaves in the 

 jungle. It seemed to play the same part in reducing the vegetable debris to humus as is 

 usually done by earthworms, which are extremely local and scarce in Aldabra. 



Three different forms of Chilopoda were obtained, the largest about 3 inches long. 

 All were found under stones, dead leaves, etc., but only one, the largest, was at all 

 common. 



(g) Arachnida. One species of scorpion is common, especially near the settlement. 

 A large variety of spiders await determination. Phalangids were altogether absent. 

 Chetifers (Chemeidae) were represented by three kinds, all apparently of different genera. 

 One was conspicuous for the large amount of silky web which it spins under stones in 

 crevices in the rock. 



(h) Mollusca. Especial attention was paid to the land mollusca. Bulimnus aldabra 

 was found to be well distributed over the whole atoll, though most plentiful at Couroupa. 

 The dry season is spent on the branches of bushes and trees, when the shell is always 

 covered with a coat of what appears to be mud ; but, from the fact that the latter is not 

 obtainable in the dry season, it is more probable that the mollusc covers itself with mucus 

 to which small particles of guano adhere. In the wet season it is hard to find, as it 

 is completely hidden by the foliage. A fresh species of land shell, a Helicinid, was found 

 on Esprit Island, but it did not seem to occur on any other part of the atoll. 



About five species of minute land shells occurred in rotting trees (especially man- 

 groves), and in the wet season in holes in rocks. 



(i) Oligochceta. Worms were represented by one earth form which was scarce in drift 

 rubbish on Esprit Island, and more common in the small area of sandy land on Picard. It 

 occurred nowhere else on the atoll, and was not found at all in the dry season. 



Malaria. In conclusion it may be of interest to mention a curious outbreak of 

 malaria which occurred. Previous to May 1908 malaria was unknown on the atoll. At 

 the end of April 1908 a steamer arrived via the Seychelles, bringing a number of labourers, 

 among whom were several men from Nossi Be, Madagascar. A little over a fortnight 

 after their arrival several cases of malaria occurred, and during the dry season the number 

 increased, the maximum being reached when the disease had as victims two-thirds of the 

 entire population of the atoll, which at the time numbered 150. 



During August the number of fresh cases decreased, and none were recorded after 

 September, though many still suffered from the disease. It was at first thought that the 

 epidemic could not be malaria, though showing every symptom of tertian fever. Men 



