58 First Report on Economic Zoology . 
Further correspondence on this subject was received from Coun- 
cillor Walter Dannatt, of Blackheath, who, writing on April 1st, 1902, 
states that : — 
We have been much troubled with gnats and mosquitoes in this 
neighbourhood, the last two summers especially, and I thought something 
might be done to abate the nuisance. ... I proposed to have a solution 
of petroleum put in the ponds on Blackheath and the neighbourhood to 
destroy the larvae, and I thought if all householders who have rain-water 
tanks and tubs were to put some petroleum into their receptacles that 
many of the Culex would then be destroyed. Will you kindly inform me 
when the breeding season of these insects is ? I may say that these pests 
have been so troublesome in this neighbourhood that most people dare not 
sit in their gardens of an evening in the summer. Many people have been 
laid up by bites from these insects. 
British Museum (Nat. Hist.), 
Cromwell Road, S.W., 
4 th April, 1902. 
To Councillor Walter Dannatt, Blackheath. 
Dear Sir, — Your letter regarding the above subject has reached me. 
In November of last year I had some correspondence from the Public Depart- 
ment of Health of the Borough of Greenwich on this same subject. I wrote 
to Dr. Annis, the Medical Officer of Health, saying I could not give any 
definite advice, as I did not know what the biting insects were. Much 
depends on the species of Culex or Anopheles. Do you know, or can you give 
me any idea of the character of the Culex. C. dorsalis and C. pipiens occur 
along the Thames. The former is a very vicious biter, and I have known it 
cause much annoyance in the docks and at Rochester. C. pipiens also bites 
at times, but may never do so in some districts. The two Anopheles 
breed in different ways. A. bifur catus is in the larval stage in the winter, 
A. maculipennis in the spring and summer, but the former occurs again in 
the summer in larval stage. C. pipiens larvae occur from May onwards in 
tubs, cisterns, etc., mostly in June, July and September. Culex dorsalis 
I have found in small artificial collections of water in July, but it probably 
also occurs in May. I am afraid only a careful examination will help you. 
I should paraffin the ponds for Anopheles (1) in winter ; (2) in May and 
June ; for Culex (1) May and (2) July and September ; much depends on 
local circumstances. For instance, Anopheles larvae occur in ponds, ditches, 
rivers and canals, in stone troughs and in rain-water barrels. So much 
ground has to be covered, but I fully expect the pests you have are Culex , 
probably both C. dorsalis and C. pipiens , which will be much easier to get rid 
of. I have some exact data of larval appearance at home, and I will look 
this up and send you. I expect you know all about the way of treating 
the water to kill the larvae ; if not, I shall be pleased to help you. 
Without knowing the district and local conditions I cannot help you as 
I should wish. I think I said this to the Officer of Public Health. 
Any further information I can give you I shall be very pleased to do. 
I am, etc., 
Fred. Y. Theobald. 
