348 INSECTS. 



a venomous fluid into the wound, which creates inflam- 

 mation, while the swelling is caused by a pouring of 

 fluid from the vessels into the tissues around, an effort, 

 probably, to free the blood from the poison, but also 

 having the effect of rendering the little blood-sucker's 

 draught easy and more copious. It has long been 

 a fact familiar to many people that the bite of a 

 Gnat which is allowed to suck its fill, is much less 

 troublesome afterwards than that of an insect disturbed 

 while sucking. Humboldt has stated this of a South 

 American Gnat, and is quoted by a writer in the 

 " Zoologist," who had found the same thing true in 

 England. In a paragraph recently extracted by the 

 Times from an American paper, a gentleman who has 

 lived for years in a Mosquito country, states the same 

 fact, and accounts for it by saying that the Gnat 

 having leave to drink his fill, sucks back, the poison 

 together with the blood. 



The lively Gnat larva^ are well known, as, with the 

 big-headed, tadpolish, jerky pupas, they are to be found in 

 .abundance in all standing water, not only in ponds and 

 ditches, but in cisterns and tanks, and occasionally in 

 our very water-jugs. 



Yet tenfold the number of larv which our eyes have 

 ever looked upon would not seem enough to account for 

 the cloud-like myriads of Gnats which are often seen 

 filling the air. In the " Insect Miscellanies" a swarm 

 is recorded so dense as to have appeared like smoke 

 issuing from the spire of Salisbury Cathedral, giving 

 rise to an alarm of fire. It is not possible to conceive 

 the immense number of such minute creatures which 

 must be congregated together to become visible at so 

 great a height. 



