292 
MONICA TAYLOR. 
The rafts found in May and June were evidently those laid 
by the hibernating imagines seen in the previous autumn, since, 
after that date, eggs were not abundantly produced until the 
middle of July, when a spell of exceptionally warm, moist, 
weather conduced to an abnormally abundant supply. This 
supply continued to be good until the middle of August, 
when the spell of hot weather ceased. Odd rafts were 
occasionally found until the end of August. 
In one of his letters Dr. Woodcock expressed his opinion 
that the rafts were deposited at about 5 o’clock in the 
morning, and text-books also state that the early hours of 
summer mornings are chosen by the gnats for the purpose 
of egg-laying. On July 12th, 1915, an egg-raft, cream-white 
in colour, was found at the Bearsden pond at 5 a.m. Portions 
of this raft were fixed at intervals of a quarter of an hour, 
and sections showed that it was quite young. After a care- 
ful study of ponds A, B, C, and D it became clear that, at 
Milngavie, most rafts are laid between the hours 9.30 p.m. 
and 12 p.m., very few between 12 p.m. and 4 a.m., and some 
between 4 a.m. and 6 a.m. As the season advances fewer are 
laid in the morning hours. Damp heat conduces greatly to 
the deposition of rafts, many more being forthcoming after a 
day of calm, moist, close weather. Numerous imagines were 
always hovering over the ponds in the evenings at a height of 
about six feet. These disappeared during the day time. 
No difficulty in rearing the larval and pupal stages of the 
gnat occurred until the summer of 1915 — the critical period 
in the life-history of the Culex being apparently the imago 
period. Even in exceptionally favourable circumstances the 
number of egg-rafts deposited at any one period bears a very 
small proportion to the number of imagines that escape from 
the pupal cases, and this has been very marked in a long 
study of the naturally occurring ponds. However, in the 
ummer of 1916 Daphnia were introduced into the gnat 
cultures at Notre Dame, and since these, like the Culex larvas, 
also flourish well on a diet of Chlamy dom on as, the tub 
quickly became swarming with Daphnia, while the gnat 
