104 NEW YORK STATE MUSEUM 



Long Island, N. Y. being particularly numerous in the vicinity of 

 the salt marshes. It assembles in large numbers in the horse sheds 



and is a serious an- 

 noyance to animals 

 tied thereunder. A 

 significant fact in 

 connection with this 

 species is the state- 

 ment by several re- 

 liable observers to 

 the efifect that a few 

 years ago when con- 

 siderable oiling was 



Fiff. 14 Green-headed horsefly, much enlarKcd (Original) . , ^ 



done for the sup- 

 pression of mosquitos. these pests were much less abundant than 

 during the last year or two, when ditching operations have been 

 relied upon more largely for mosquito control. This latter seems 

 to have had no effect upon the horseflies, as was attested by their 

 abundance about the salt marshes last July while mosquitos were 

 conspicuous because of their absence. 



These observations are particularly gratifying as they bear out 

 the results obtained in Russia by Professor Porchinski, who found 

 that the adults were destroyed if there was an oily film on forest 

 pools frequented by them. Horseflies or Tabanidae have a habit 

 of repeatedly drinking from favorite damp, woodland pools and in 

 that way may come in contact with the oil and perish. Similar 

 results on a smaller scale were obtained in this country by Dr 

 Howard. The application of oil to pools is now generally regarded 

 as merely a temporary expedient for checking the multiplication of 

 mosquitos, but it seems to be of considerable value in destroying 

 horseflies and might be employed to advantage wherever these in- 

 sects are unusually numerous and annoying. The only essential 

 is that there be a film of oil on the pools when the horseflies are 

 abundant, something self-evident to any resident. The more pools 

 treated the greater the chances of success and it is very probable 

 that a little observation would result in finding the pools most 

 favored by these insects and thus result in a great saving in con- 

 trolling the pest without materially diminishing the effectiveness 

 of the method. 



Giant water bug (Belostoma americanum Leidy) . 

 A specimen of this gigantic brown water bug was received July 5 



