II FLIES WITH AQUATIC LARVJE in 



cold weather, and only becomes intense during great 

 summer heat. 1 



Nearly two hundred species of Gnats have been 

 described. Some of these inhabit hot countries, and 

 are popularly known as Mosquitoes, but to the 

 zoologist there is no species of insect which can be 

 defined as the Mosquito. Even in our own temperate 

 climate a burst of hot summer weather has led 

 persons who might be supposed to be pretty good 

 judges to give the name of Mosquito to our common 

 Gnat. "A few years ago a London Hotel, popular 

 with American visitors, was said to harbour Mosqui- 

 toes, which some of the visitors had brought with 

 them from the Southern States, but an examination 

 revealed the fact that the cistern was uncovered and 

 exposed, and was the breeding place for hosts of 

 Gnats." 2 



The piping sound which the Gnat utters, and which 

 is often of itself enough to excite the greatest irritation 

 in its victims, is said to be due to the vibration of 

 the edges of its spiracles, occasioned by the passage 



1 Some Gnats can subsist upon the juices of ripe fruits, 

 where they are unable to feed on the blood of animals. 

 Many two-winged flies of the section Nemocera have the 

 rostrum and mouth-parts remarkably prolonged, apparently 

 for sucking sap or nectar. Apetz has observed a Campylomyza 

 (Cecidomyidas) sucking a caterpillar, and both Culex and 

 Simulium are known to suck caterpillars. Culex and Anopheles 

 (Culicidas), some species of Ceratopogon (Chironomidae) and 

 Phlebotomus (Psychodidse), are various examples of blood-suck- 

 ing Nemocera. The substance of this note is taken from Baron 

 Osten Sacken's " Characters of the Three Divisions of Diptera," 

 &c., Berl. Ent. Zeits. Bd. XXXVII. (1892). 



- Enc. Brit.,\ r v\. II. p. 866. 



