274 Insecta. 



(IV) General bionomics. These species appear to depend for their con- 

 tinued existence in good numbers, on their adaptability for being the first insects 

 to employ newly-formed pools for breeding. In these there is little or no struggle 

 for existence, food being abundant and enemies absent: later, Neuroptera, Coleo- 

 ptera etc. appear, and as the pools become stagnant and crowded, disease be- 

 comes rife among the larvae. The author concludes that the struggle against ene- 

 mies is greatest in permanent waters containing fish (the greatest destroyers of the 

 larvae) and other predaceous creatures, and almost non-existent in recently-formed 

 non-permanent waters: while that against disease is more or less great in waters 

 that have been stagnant for more than a short period. Thus, recently-formed 

 non-permanent situations are the most favourable breeding-grounds. The imagines 

 are unobtrusive and purely nocturnal, biting all through the night. It was shown 

 experimentally that the females, in selecting breeding-places, prefer water con- 

 taining decomposing vegetable or other matter in Suspension to absolutely clear 

 water, and that the size of the pool is of some importance. The adults have a 

 struggle for existence. Wind and heavy rains are very adverse to them: many 

 kinds of spiders prey on them, their webs often forming dense networks over 

 pools containing larvae: lizards, small frogs, and dragonflies also devour them. 

 The females appear to fly no further than the nearest blood-supply; in certain 

 cases they frequent the side of a small village nearer to their breeding-place but 

 do not travel as far as the further side. 



(V) This section deals with methods for ascertaining the distribution of 

 the larvae. (VI) In this the breeding-grounds are classified as: (a) Non-per- 

 manent waters, i. e. those formed after heavy or continuous rainfalL The most 

 important are found in marshy lands which become water-logged, the water dis- 

 appearing quickly after a few days and leaving only some deeper pools. These 

 situations are the greatest producers of Anophelines in the Island; the larvae 

 and adults being found in those parts of them which are sheltered by bush etc. 

 to some extent. (b) Altered permanent waters, including such situations as pools 

 caused to spread by rain, accumulations of water formed by obstruction of water- 

 courses through human agency etc. (c) Permanent waters, such as river-edges, 

 artificial tanks etc. The adaptability of rivers depends largely on the speed of 

 the current, for while larvae cannot live in swiftly-running waters, they may live 

 in sluggish parts of the same river. These situations produce some Anophelines, 

 but are relatively unimportant. (d) Anopheline larvae are absent from small col- 

 lections of water such as those in disused domestic Utensils, bromeliads etc. 

 (Vn) In this section the effect of rainfall is discussed. It is not so much the 

 amount as the nature of the rainfall which influences the numbers of Anophelines: 

 for instance, two months miglit have an equal amount of rainfall, but it might 

 be even and continuous in one, and torrential and intermittent in the other: the 

 former would then be much more favourable. The dense mountain-forests are 

 free from Anophelines, because the continuous rain washes out the pools, while 

 the forest screens them from sunlight. (VIII) In the conclusion the writer em- 

 phasises the need for careful research before remedial measures are taken. Tables 

 of rainfall are added, and the plates illustrate various types of breeding-ground. 



H. Scott (Cambridge). 



895) Collin, J. E., Diptera, Borboridae [of the Seychelles]. In: Trans. Linn. 

 Soc. London (Ser. 2, Zool.), Bd. XV, Heft 1, S. 101—104, 1912. 



896) _, Phoridae [of the Seychelles]. Ibid., S. 105—118, Taf. 5, 1912. 



These two reports on the material collected by the Percy Sladen Trust Exp. have 

 a considerable interest regarding Geographica! Distribution. Of the 9 spp. of Borboridae, 



