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 thoir 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. 



Bbitish Museum (Nat. Hist.), 



Cromwell Road, S.W., 



Wi Apiil, 1902. 



To Councillor Walter Dannatt, Blackheath. 



Dear Sir, — Your letter regarding the above subject has reach<idme. 

 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. jJipiens occur 

 along the Thames. The former is a very vicious biter, and I have known it 

 <3ause much annoyance in the docks and at Eochester. C. pipiens also bites 

 at times, but may never do so in some districts. The two Anopheles 

 breed in different ways. A. hifurcatus is in the larval stage in the winter, 

 A. macuUpenms in the spring and summer, but the former occurs again in 

 the smnmer 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 Cidex (1) May and (2) July and September ; much depends on 

 local circumstances. For instance, Anopheles larvte occur in ponds, ditches, 

 rivers and canals, in stone troughs and in rain-water baiTels. 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 larva ; 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. V. Theobald. 



