ON THE MOSQUITOS OF MACEDONIA. 3 



Among the factors favourable to the larvae, one noted, especially in the streams, 

 the shelter afforded by watercress (Nasturtium officinale). Floating pieces of weed 

 uprooted by water-birds in feeding also often harboured larvae. In the lakes the 

 dense formation of Salvinia frequently found inshore was clear of larvae except 

 along its outer edges ; larvae also were to be found in clear spaces enclosed by this 

 fern. Patches of Spirogyra were a sure draw for larvae, which in such a situation 

 were often very inconspicuous owing to the green contents of the gut. 



Genus Anopheles, Mg. 



It is difficult, after so short an experience, to speak with finality on the relative 

 abundance, distribution and seasonal prevalence of the following four species of 

 Anopheles, nor would any figures of, for example, the percentage that each species 

 formed of the total specimens examined (unless based on collections made in a 

 great variety of situations throughout a whole season) be of particular value. We 

 observed, however, a decrease in the numbers of maculipennis, with a corresponding 

 increase on the part of palestinensis towards the end of August and throughout 

 September. But whether the abundance of the latter species has any direct relation 

 to the rise in the curve of subtertian malaria is still undetermined. There was, in 

 1917, no well-defined end to the mosquito season ; maculipennis, palestinensis and 

 sinensis entered our camps in decreasing numbers to about the middle of November 

 (Karasouli District). But for three weeks later occasional active specimens of 

 maculipennis were taken on the wing. The larvae too are very resistant to cold and 

 may continue to show activity under a covering of ice. Lt.-Col. C. M. Wenyon 

 even records a case in which after the water in a basin containing maculipennis 

 larvae had been frozen into a solid block he succeeded in resuscitating them by 

 thawing and four hours' exposure to sunshine. 



Anopheles maculipennis, Mg. 



We found this species everywhere throughout the season, but the numbers 

 observed varied considerably. At Karasouli in July and early August it was 

 apparently the dominant form as imago, and probably as larva also. At Lahana 

 however by the middle of the month maculipennis was distinctly scarcer. Its 

 numbers began to recover about mid-September and Lt.-Col. Wenyon found it 

 common in October. At Karasouli I believe a similar fluctuation was observed. In 

 October I found maculipennis and palestinensis both in numbers there ; and on 

 evenings when sinensis put in an appearance, the three species were about equally 

 represented. The later examples of this species were larger and more distinctly 

 spotted, particularly the females, than those taken earlier, in some of which the 

 spots were nearly absent even in bred specimens. Such examples closely approach 

 bifurcatus in size and general appearance, and as a matter of fact many mosqiiitos 

 sent us as the latter species proved on examination to be maculipennis. 



Anopheles bifurcatus, L. 



Although eventually discovered in a variety of localities this species was nowhere 

 numerous ; it may however prove to be abundant in the spring. The first undoubted 

 examples seen were bred from larvae taken early in September from a well and 

 (C455) 



