MOSQUITOS OF THE PALAEARCTIC REGION. 271 



The species has a rather close resemblance to the Oriental A . aitkeni, and, as 

 suggested by Barraud, it is probable that the specimens of A. aitkeni recorded from 

 Palestine were really A. algeriensis. A. aitkeni is certainly a distinct species, since 

 the upright scales of the head are very much narrower than in A. als^eriensis, and 

 the side-pieces of the hypopygium have two distinct basal spines. 



Distribution. — Algeria [Sergent) ; Italy [Hargreaves) ; Macedonia [Waterston) ; 

 Palestine [Austen. Barraud) ; Egypt {Austen) ; Mesopotamia {Christopheys). 



2. Anopheles (Anopheles) bifurcatus, L. (fig. 2, c). 



CuJex hifurcatus, Linnaeus, Syst. Nat. Ed. x, p. 603 (1758). 



Culex claviger, Meigen, Klass. u. Beschr. i, p. 4 (1804). 



Cnlex trifurcatus. Inibricius, Ent. Syst. iv, p. 401 (1794). 



Anopheles villosus, Robineau-Desvoidy, Mem. Soc. d'Hist. Nat. Paris, iii, p. 411 

 (1827). 



Anopheles grisescens, Stephens, Zool. Journ. xii (1828). 



Anopheles antennatus, Becker, Mitt. Zool. Mus. Berlin, ii, p. 68 (1903). 



This species varies a good deal in size and colour ; small dark specimens might 

 be mistaken for A. plumheus and small light ones for .4. algeriensis. Apart from the 

 male hypopygial characters, which are absolutely diagnostic, A. bifurcatus may 

 readily be separated from .4. plumbeus and A. algeriensis by the other characters 

 mentioned in the key. 



The larva, which has been fully described by Lang, occurs generally in clean 

 water with some weed, in rather shady situations ; in the Mediterranean region it 

 is frequently found in wells. The winter is passed in the larval stage, the adults 

 dying off in the late autumn and the first brood appearing again in early spring. 



A. bifurcatus is less domestic than A. maculipennis and does not so readily 

 enter houses, but bites freely in the open. 



Distribution .-—Throughout Europe, North Africa (except desert regions) and 

 Asia Minor. Turkestan [Vassiliev). Not found as yet further east. Apparently rarer 

 in the far north. 



South European specimens are commonly smaller than those from Central and 

 North Europe, but are not otherwise distinguishable. 



3. Anopheles (Anopheles) plumbeus, Stph. (fig. 2, a). 



Anopheles plumbeus, Stephens, Zool. Journ. iii, p. v503 (1828). 



Anopheles nigripes, Staeger, Kroyer's Nat. Tidschr. h, p. 552 (1839). 



The general black colour, densely and uniformly scaled wings, white scales on 

 front of mesonotum, conspicuously hoary stripe down centre of mesonotum, ' and 

 conspicuous white frontal tuft, will suffice to distinguish this species from those 

 with which it might be confused. 



The larva and egg have been described by Lang, Eysell, and Carter and Blacklock. 

 A. plumbeus is the only species in the Palaearctic fauna which is known to breed 

 in rot-holes in trees, and the very striking characteristics of the larva aU seem to be 

 correlated with this habit. As has already been pointed out by Christophers, tree- 

 hole larvae of different genera of mosquitos commonly show three forms of modifi- 

 cation : (1) a reduction of the hairs on the head, and especially of the small bristles 

 on the antennae ; (2) an increase and enlargement of the hairs on the thorax and 

 abdomen ; and (3) a development of chitinous structures on the last few abdominal 

 segments. All these points are well illustrated by A. plumbeus. The tree-holes 

 in which these larvae are found are frequently (perhaps usually) dark, and it may be 

 supposed that the sense of sight would be of little value to the inhabitants of such 

 places, while that of touch would attain a greatly enhanced importance, since the 

 (4183) u2 



