MALARIA, MOSQUITOES AND THE ESSEX MARSHES 37
ing 105° F. or more. This fever continues for variable periods up
to twenty-four hours or more, and then abates with profuse
sweating.
The life-history of the mosquito is well known to all: the eggs
are laid in water, and the larvae pass their whole existence there,
as also do the pupae, from which the adult insects emerge.
Of the thousand or so species of mosquitoes in the world, only
members of the sub-family Anopheles are able to transmit human
malaria. In England, we have four species of Anopheles, but the
only one which is of importance in malaria-carrying is A. maculi-
pennis.
A. maculipennis larvae were, in 1900, collected in Essex from
Lexden, Bottle End (near Colchester), Heybridge, Rochford, Pit-
sea, West Tilbury, Corringham, Ongar, Bulphan, Vange, Ocken-
den, Hornchurch and Rainham.
Until recently it was considered that this species was made
up of a number of varieties or sub-species. It is now generally
accepted that these are, in fact, quite distinct species, even though
it may not always be possible to classify them by morphological