372 



Marvels of Insect Life. 



of view ; but it is possible that some of us who are badly tormented by Insects 

 may in return cause serious mortality among our little persecutors. 



But the point we wished to make plain is this — that gnats are mosquitoes, and 

 that mosquitoes are only gnats translated into Spanish. This will be unconvincing 

 to the people who think it is more interesting to be bitten by mosquitoes than bv 

 common gnats ; just as they would be rather pleased to tell you they suffer from 

 arthritis, but are ashamed to confess to so vulgar a complaint as gout ! Let it also 

 be understood that these terms — gnat and mosquito — are general, like butterflv 

 and moth, and do not indicate any particular species. We have in this countrv 

 alone about a dozen species of gnat, and they do not all belong to one genus, or 

 even to the same family. From the popular point of view it is unnecessary and 

 rather absurd to distinguish between species of flies that appear so much alike 



that only specialists can sepa- 

 rate them ; but there are 

 marked differences in the early 

 stages. 



•~\ 



The common gnat ^ has an 



aquatic grub about a third of 

 an inch long, with a swollen 

 fore-body and a long, slender 

 hind-body of nine segments, 

 but no legs. It has the pecu- 

 liar habit of hanging, as it were, 

 from the surface-film of the 

 _ water, head downwards. It is 



X^j^ ^^k enabled to do this— in spite of 



'0\ ^L its being heavier than water — 



^ owing to its possession of a 



-<«» tube which starts off at an 



^ angle from the eighth segment, 



■ and ends in five flaps. This 



tube is in connection with the 

 internal air-tubes, by means of 

 which Insects get their blood 

 supplied with oxygen, \\hen the gnat-grub dives into the depths of its stagnant 

 pool or water-butt, the tube is closed by the five flaps meeting in a point ; but when 

 it is feeding head downwards at the surface the flaps are spread out and lie upon 

 the surface, in such manner that they form a shallow funnel which at once admits 

 air for respiration and buoys up the grub. The head bears a number of delicate 

 lashes by whose movements microscopic food is directed to the mouth. 



After incessant feeding and several changes of skin, the grub becomes a chrysalis. 

 It now bears some resemblance to a minute tadpole, for its head and fore-body are 

 conjoined like the head and body of the tadpole, whilst the long, slender hind-body 

 of the gnat resembles the tail of the tadpole. The gnat-chrysalis has what may 

 more fitly be called a tail consisting of two lobes at the end of the hind-body, which 



^ Culex pipiens. 



[//. 5. Cheavin, F.R.M. 



Pholo by] 



Head of Female Gnat. 



The headof the female is here shown on a scale of thirtv times the actual size 

 The sucking extremity of the long proboscis is shown, with the accompanying 

 lancets by which the incision in the victim is made. 



