270 OBSERVATIONS ON INSECTS. 



playing about in the air on a summer's evening con- 

 sist exclusively of this last sex. 



Oct. 5, 1828. Stinging gnats of various species, 

 but more particularly the Culex pipiens and the 

 C. annulatus of Meigen, abound in houses this au- 

 tumn to a degree far surpassing anything I re- 

 member in former years. The cellars especially 

 are swarming with myriads, which blacken the walls 

 and ceilings with their numbers. This I attribute 

 to the wet summer.* 



and that is, that if, when it has once fixed its sucker, " it be left 

 to suck to satiety undisturbed, no swelling takes place, and no 

 pain is left behind." He says, " We often repeated this experi- 

 ment on ourselves in the valley of the Rio Magdalena, by the ad- 

 vice of the natives. It may be asked, whether the insect deposit 

 the stimulating liquid only at the moment of its flight, when it is 

 driven away ; or repump the liquid, when it is left to suck as much 

 as it will. I incline to this latter opinion ; for, on presenting 

 quietly the back of the hand to the Culex cyanopterus, I observed 

 that the pain, very violent in the beginning, diminishes in propor- 

 tion as the insect continues to suck ; and ceases altogether, when 

 it voluntarily flies away." Id. p. 114. 



I have not noticed anything like this in the case of our English 

 Culices. Neither did I find, on mentioning Humboldt's statement 

 to Sir Robert Schomburgh, who has travelled over the same parts 

 of South America, and felt all the annoyance experienced by 

 Humboldt and Bonpland from the attacks of these insects, that 

 he could confirm it by his own observation. 



* However gnats may occasionally abound, and annoy us, in this 

 country, we can form but a small idea of their immense numbers 

 in some other countries, particularly Equinoctial America. Hum- 

 boldt observes, that " persons who have not navigated the great 

 rivers in that part of the world, for instance, the Oroonoko and 

 the Rio Magdalena, can scarcely conceive, how without interrup- 



