298 MR. F. BALFOUR BROWNE ON AQUATIC COLEOPTERA. 
crawl out of them as I have constantly found the larvae hatched 
in a tube containing a few egg-bearing imagos. It is easy, 
therefore, to observe the “ spawning ” period of this genus. 
The first record of eggs last year was made on May 8th, but 
they were not common until towards the end of the month. 
There was no record of eggs in August of last year, but in 
1904 there were three records for this month, the last being 
on the 27th. The egg period, therefore, apparently lasts 
from May to August, the period, according to the curve, 
when the Palpicornia are most distributed. The egg-cocoons 
of Hydrophilus piceus, L. are to be found sparingly in the 
dykes in this district in June, and one specimen in captivity 
laid its eggs in that month. Hydrobius oblongus, Herbst., 
also produced its ribbon-shaped egg-cocoon in an aquarium 
in June, 1905.* I have only one record for the Hydradephaga ; 
I found a female of Dytiscus marginalis , L., depositing her 
eggs in April, the usual egg-laying period of this species being 
given in books as March and April. 
My observations as to larvae have also been very few but 
they should perhaps be included. The earliest well-grown 
larvae of which I have a note, are those of one or more species 
of Agabus, which in 1904 were observed in March and April, 
and in 1905 as “ nearly full-grown ” in April and May. I first 
observed Dytiscus larvae in April, well grown specimens of, 
I believe, D. circumflexus, F., from the fact that where they 
occurred, I have only taken that species. 
I have no records of any other well grown larvae until June, 
when Pelobius, Hyphydrus, Dytiscus, Acilius, Gyrinus, and 
Hydrophilus all occurred. In August again I found Hyphydrus 
common, a few Pelobius, and one or two full grown Hydrophilus. 
After that month no full grown larvae are recorded, but numbers 
of small larvae were found in September. At one place, 
among Chara I found a number of very small Haliplid larvae, 
which I believe had only hatched a short time previously. 
In October I recorded half grown Agabus larvae in one pond. 
With regard to immature specimens of imagos my records 
* The egg cocoons of Hydrobius fuscipes, L., and picicrus, Thoms., have 
occurred this year, 1906, sparingly in March and commonly in April. 
