167 



For destruction of the larvae, which breed chiefly in rotting straw, 

 all straw stacks, particularly oat stubble, should be carefully piled on 

 a clean floor so that they will not become damp. Any unusable stubble 

 should at once be removed. As manure-heaps also serve as breedmg- 

 places, all litter should be removed from stables at least once every 

 three 'days, and the surface of manure heaps should be constantly 

 moved in order to expose the larvae to air, sun, and their natural 

 enemies. 



Grassi (B.). Osservazioni suUa Biologia degli Anofeli. [Observations 

 on the Biologv of Anopheliues.j— .l/nr. d' Igicne, Rome, xxxi, 

 no. 6, June 1921, pp. 329-349. [Received 8th August 1921.] 

 The term " hibernating " may be rightly applied to Anophelines 

 that are fat and do not contain blood, and the author believes that the 

 females emerging in the environs of Rome in late autumn (at the first 

 onset of cold\veather) suck blood after being fertilised and digest it ; 

 the eggs, however, remain small in size and the mosquitos become fat. 

 The intestines of fat individuals are empty, and no success attended 

 repeated attempts to make these mosquitos bite. It is not known 

 whether more than one meal is needed to ensure fattening. In the 

 Roman climate only a limited number of individuals become fat. 

 They have to remain in surroundings that are not warm enough to 

 cause the ingested blood to be used for maturing the eggs. In the 

 last months of the }'ear the appearance of fresh fat indu'iduals is always 

 possible. . 



It may be thought that fattening is an annual occurrence m the lite 

 of the species independent of temperature. In this connection the 

 author thinks it possible that in late autumn Anophelines can fatten 

 when the surrounding temperature is, on the whole, warmer than in 

 spring, at which latter season the maturing of eggs takes the place of 

 fattening. This is quite probable and may be explained by assuming 

 that in spring Anophelines prefer— to a greater degree than in autumn- 

 warm situations promoting the maturing of eggs instead of fattening 

 It is, however, certain that hibernation is not a necessary link m the 

 continuation of the species. Some individuals wuth developing or 

 mature eggs may be found contemporaneously with fat specimens. 

 At the beginning of winter Anophelines that contain no blood and 

 are thin may be found. Some of them have emerged recentl}-, and 

 others have been fat and have become thin once more. 



The spring awakening of Anophelines is doubtless connected with 

 loss of fat. Individuals that have suffered such a loss leave their refuges 

 and assemble in the sheds of domestic animals. In Anophelines that 

 have lost fat the eggs are always in the backward condition they were 

 in before fattening and they do not grow in size unless blood is taken. 

 An Anopheline that has hibernated {i.e., lost fat) can mature its eggs 

 as the result of one blood-feed ; the author does not believe this to 

 be exceptional. It is certain that at least some of the first indn'iduals 

 that mature at the end of winter have a smaller abdomen than others 

 and produce a smaller number of eggs. 



The above data apply to Anopheles inaciiUpennis {clainger), but 

 A. bifiircatus exhibits similar phenomena. 



It is possible that the malaria epidemics that occur in spring in 

 northern countries may be related to the awakening of Anophelines 

 (that have hibernated, i.e., lost fat) containing sporozoits in the salivary 

 glands. This is important because Anophelines that are not fat may 



