380 BRITISH BIRDS. 
Genus HYPOLAIS. 
The Tree-Warblers were included by Linneus in his comprehensive ~ 
genus Motacilla. Bechstein afterwards placed them in the genus Sylvia, 
which Scopoli had made for the Warblers. Various writers have at 
different times separated the Warblers into different groups, amongst 
whom was Brehm, who, in the ‘ Isis’ for 1828, p. 1283, founded the genus 
Hypolais for the Icterine Warbler, which therefore becomes its type. 
Brehm, following Linneus, misspelt this word “Hippolais,’ under a 
mistaken idea of its derivation. 
The genus Hypolais contains a small group of birds chiefly remarkable 
for laying eggs having a French-grey or salmon-coloured ground-colour. 
They form the connecting-link between Phylloscopus and Acrocephalus, 
having the nearly even tail of the former and the large bill of the latter. 
From the large-billed subgeneric group of the former (Acanthopneustes), 
besides the difference in the coloration of the eggs already alluded to, 
they can only be distinguished by the absence of the pale tips to the wing- 
coverts—which in Acanthopneustes form one, and often two pale bars across 
the wings. There are four well-defined species belonging to this genus, 
three of which do not exhibit any great variation of size, wing-formula, or 
colour. ‘The other species is perhaps more variable than any other member 
of this large subfamily, and may be divided into six or more races, which 
are tolerably distinct, although connected together by mtermediate forms. _ 
The T'ree-Warblers frequent wooded localities, bush-covered marshy 
districts, gardens, and thickets. All the species of this genus possess con- 
siderable powers of song. They build beautiful cup-shaped nests ; and their 
eggs are from four to six in number. Their food is chiefly composed 
of insects, which they search for amongst leaves and twigs and frequently 
capture in the air. 
The basin of the Mediterranean appears to be the centre of distribution 
of this genus—one or two species extending their range more to the east, — 
one of them as far as Lake Baikal. One species only is a rare straggler to 
the British Islands, 
Bictoran. 
ee 
