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October. The larvae of A. bifurcatus were found in drains, swamps 

 and garden- wells, chiefly in the first two, and in isolated localities 

 instead of in localities distributed over the district as was the case 

 with A. macidipennis. Full details are given of the conditions under 

 which A. bifurcatus occurs near Fiumicino. Owing to its comparative 

 scarcity in the region around Rome, it is of no importance in the spread 

 of malaria. 



Eggs of A. maculipennis deposited on 8th February began to hatch 

 in 14 days in a room and in 16 in a pig-stye where the water froze 

 during a cold period, showing that freezing, in natural surroundings, 

 does not interfere with development. During the early months of the 

 year larval development requires about 2 months. At the end of May 

 and in June this time may be reduced to 28 days, and in August to 16. 

 Speaking generally oviposition begins in February. The author 

 believes that there are 7 annual generations of A. maculipennis in 

 this region. By generations he means the progeny resulting from the 

 first consecutive ovipositions, as owing to the interval between the 

 first and last ovipositions of a given female, her progeny at a given 

 date may apparently belong to different generations. As the tempera- 

 ture falls at the end of the year the larvae become torpid. On 12th 

 November, the air temperature being 10° C. (50° F.), a larva was 

 observed to remain under water for 10 minutes. This never occurs in 

 summer. At very low temperatures the larvae may remain under 

 water for days ; they cease to feed and to grow. The hibernation 

 of A. maculipennis, as in general of all Anophehnes, shows that 

 hibernation depends on climate and must be regarded as an adaptation. 

 The nymphal stage lasts about 7 days in April and May and 50 hours 

 early in August. 



According to the observations made, the influence of vegetation on 

 the development of the larvae is not due to chemical action on the 

 water, but solely to physical action. Speaking generally, vegetation 

 may be divided into horizontal or superficial and into vertical or 

 emerging. The former is favourable to A. maculipennis, w^hile the 

 latter is unfavourable to that species and more favourable to A , bifur- 

 catus. The character of the ground around the marshes naturally 

 re-acts on them, and therefore it is foimd that marshes with a hori- 

 zontal vegetation are found in wood-less tracts, such as pasture or 

 cultivated land, which represent a more domestic condition, whilst 

 marshes with a vertical vegetation occur in bushy locahties. In the 

 latter type of marsh there is more shade and the water is colder than 

 in the former type suited to A. maculipennis. 



A full list of marsh and canal plants of the region is given. The 

 following are those most favourable to A. maculipennis: — Ranunculus 

 aquatilis, Zannichellia palustris, Potamogeton pectinatus, Myriophyllum 

 spicatum, and Ceratophyllum demersum. Many of the marshes in 

 the non- wooded zone s become covered at the end of winter with a 

 carpet of Ranunculus. Not only does this supply a support and 

 food, but it divides the water into two strata, that at the surface 

 being well-lit and warm and forming a perfect breeding place for the 

 larvae of the hibernated adults of A. maculipennis. Deep water is not 

 in itself unsuitable to the larvae, but only so to the extent that it pre- 

 vents the growth of vegetation ; when vegetation reaches the upper 



