ESSEX REPTILES AND AMPHIBIANS. 151 
happen if the animal is sickly, and I have had myself awful cases 
of chameleons (and once a bat) destroyed in this way. The 
greenbottle, so disgustingly common in London gardens 
(Lucilia sp), will lay its eggs in the nostrils of a living tortoise, 
but I have never seen this happen to a frog or a toad. One-eyed 
toads, I am sure, are animals which have swallowed either blue¬ 
bottles or greenbottles. 
5. —THE FROG (Rana temporaria). 
I recorded “ one year ” frogs on the 17th March, in 1917 ; 
and, as with the toad, they seem to be constantly earlier than 
the “ two year old’s.” A collector who supplies the frogs used 
in London hospitals and schools has often assured me that he 
finds all three stages wintering together at the bottom of ponds. 
These congregations are very great. In October, 1912, he took 
1,400 frogs in two days from a drain at Uxbridge ; and in Decem¬ 
ber, 1918 he showed me part of a batch of 800 taken from a small 
pond. These, by the way, were crooning vigorously. I have 
heard frogs, deep in the water, crooning as late in the year as 
October at Theydon Bois, and it is not unusual to come across 
lively individuals at all seasons when using a net in ponds. The 
dealer I mention believes that when a pond is totally cleared 
in midwinter, it will soon be occupied again. This means, of 
course, that frogs are more active on mild winter nights than 
most of us think. 
The lake at Birch Hall accommodates many frogs, which spawn 
always in colonies. In 1914, 15, 16, and 17 the egg masses were 
scattered along a short stretch of bank on the western edge near 
the boathouse. In the latter year the eggs were all laid together 
in a single batch. During these years the increase in an area 
of Lesser Reed-Mace (Typha minor) quite altered the nature 
of the margin, which before was clay, thickly covered with 
Fontinalis and Hypnnm. The change, apparently, caused the 
frogs to migrate ; for in 1918 the spawn was deposited in a 
huge patch at the shallow western corner of the lake, a hundred 
yards away from the previous station. They used the place 
again in 1919, when much of the spawn was frozen black by the 
hard weather of March and April. 
During the six years that the lake was under observation, 
I never saw frogs’ eggs awav from their circumscribed breeding 
