Length of Egg , Larval and Pupal Stages . 55 
have hatched out in from two to eight days : Colonel Giles says 
five to ten days. In Culex pungens Professor Howard finds the 
larval life to be completed in a minimum of seven to eight days. 
The adults issue from the pupae when the latter are two days 
old. “ This gives,” says Professor Howard, “ the minimum 
generation for this species as ten days, namely, sixteen to 
twenty-four hours for the egg, seven days for the larva, and 
two for the pupa.” I have found that warmth greatly hastens 
development, and also the presence of plenty of food in the 
water. Some C. pipiens larvae kept in water rich in organic 
matter matured eight days sooner than another batch of the 
same larvae kept in pure spring water and fed scantily on 
infusoria, &c. Not only did the absence of food retard growth, 
but it made a difference of often nearly 1 * 5 mm. in the size of 
the specimens, those that had a scant supply of food being quite 
stunted. 
I do not think therefore that any definite times can be given 
for the various stages, even in the same species, temperature 
and food having such a marked influence on them within certain 
limits. Howard found the eggs of Anopheles maculipennis took 
from three to four days to incubate; those laid in April four 
days, those in May three. The egg stage is given in Ross’s 
Malarial Report (p. 19) as twenty-four hours (in vitro ) for 
Anopheles. In the same report the larval life is given as pro¬ 
bably from two to three days, considerably less, I should imagine, 
than is ever likely to take place; “but under unfavourable 
conditions,” the report continues, “ it may certainly extend to 
weeks.” Professor Howard has found that in A. maculipennis 
it takes sixteen days to mature. 
Nuttall and Shipley say the egg of A. maculipennis gives rise 
to the larva on the second or third day. The larval life, they 
say, lasts from eighteen to twenty-one days. 
Dr. Lutz sends me the following note re the length of time 
taken by Anopheles argyrotarsis, Desv., to develop : 11 Argyrotarsis 
has been bred by me from the eggs ; it takes three weeks for total 
development in favourable temperature (25° C.).” The pupal 
stage of A. maculipennis is said by Meinert to last four or 
five days, a little less in warm summer weather. Howard says 
the pupal stage varies according to weather ; the minimum period 
during June was five days, although several specimens remained 
in this stage for ten days. The whole life cycle of this species 
common to Europe and America is twenty-four days. But heat 
