II 



January 22, 1833. 

 William Yarrell, Esq. in tlie Chair. 



A letter was rcad, atidressed to Charles Telfair, Esq., Corr. 

 Menib. Z.S.,as President of the Mauritius Natūrai History Society, 

 by M. Goudot. lt is dated at Tamatave (in the island of Mada- 

 gascar), April 20, 1832, and contains an account of a remarkable 

 phfenomenon, connected with a tree of the genus Morm, which is 

 not uncommon in the vicinity of that place. From the branchesof 

 this tree, vvhich are covered withathick coriaceous foliage, there is 

 seen to fall, niore especially towards mid-day, and under the influ- 

 ence of a borning and almost vertical sun, a copious and refreshing 

 supply of limpid de\v, or rather rain. On ascending the tree an 

 explanation of this singular property is at once obtained. Around 

 the vigorous shoots, loaded with leaves, and particularly at their 

 ramifications, are found large clusters oflarva;, covered by a whitish 

 froth, in constant agitation, and pressing eagerly upon each other 

 in their attempts to apply themselves to the surface of the bark, 

 from which they extract the sap in such quantity as to maintain 

 their bodies in a statė of saturated humidity. This sap isafterwards 

 poured out, either through particular organs scattered over the 

 surface of the body, or by means of the common excretory ducts, 

 and forms drops of small size, vvhich are gradually collected into 

 larger drops, and appear to M. Goudot to escape from the bodies of 

 the larva; vvitli a rapidity proportioned to the action of _the solar 

 rays, The activity of the larvce is, in fact, increased in a corre- 

 sponding degree with the increase in the atmospheric temperature. 

 Tovvards evening, and when the influence of the solar rays is sen- 

 sibl)'^ diminished, the production of the fluid, thus singularly se- 

 creted, is partially suspended, and the drops fall slovvly ; as night 

 advances, a fevv rare and tardy drops are heard at distant intervals ; 

 until atlast they altogether cease, to be again renewed frith thefirst 

 rays of the morning sun. When fifty or a hundred such clusters of 

 larvce zve placed, as often happens, on the šame tree, it may well be 

 imagined that the secretion may become sufficiently copious to as- 

 sume the appearance of actual rain. 



Some idea of the rapidity \vith which it falls may be obtained from 

 the modein|\vhich M. Goudot collected abottleful for transmission to 

 the Natūrai History Society of the Mauritius. He statės that in the 

 beginning of February, he placed under one of the trees in question a 

 vessel capable of holding about a litre (nearly equal to an English 

 quart). The mass of larva selected as purveyors consisted of from 

 sixty to seventy individuals, about half grown ; and the sun being 

 powerful, the drops vvere very large, and fell in quick succession. 

 He estimates that, setting aside the loss by evaporation, and by the 

 animals which drank from the vessel, he could have filled thebottle 



