5 



INSECTS. 



Colorado, have also yielded fossil flies. A few have been obtained from Secondary 

 rocks. 



THE STRAIGHT-SEAMED FLIES, Suborder Orthorrhapha. 



The first section of this suborder contains the gnats and mosquitoes (Culicidw), 

 daddy-longlegs (Tipulidce), true midges (Chironomidcv), and fungus - midges 

 (Mycetophilidce). These families are sometimes spoken of collectively as the 

 Nematocera, or flies with thread-like antennae, on account of the length and thin- 

 ness of those organs, which usually consist of as many as ten or more segments. 

 The maxillary palpi also are elongate, and the body and limbs present, as a rule, 

 the type with which we are familiar in the gnats and daddy-longlegs. 

 Mosquitoes and The mosquitoes and gnats (Cidtcidai), although often regarded as 



Gnats. distinct, are in reality identical. They abound in all lands, and may 

 be met with in cold barren countries like Iceland and Lapland as well as in the 

 dense forests of tropical climes, everywhere being the plague of travellers on 

 account of their insatiable thirst for blood and the intense irritation caused by their 

 bite. It is, however, only the females that bite and suck blood, and in this 



connection it may be pointed out that 

 no members of the Diptera sting in 

 the sense in which the word is used 

 with regard to ants and wasps ; that 

 is to say, the wound, although giving 

 rise to a sharp stinging sensation, is 

 inflicted by jaws, and not, as in the 

 case of the ants, by an organ especially 

 designed for the purpose placed at the 

 hinder extremity of the abdomen. 

 The annexed figure representing the 

 banded gnat (Culex annulatus), a 

 species sometimes found in houses, and 

 noticeable for being the largest British 

 form, is selected to illustrate the mode of life characteristic of the members of 

 this family. The long slender eggs, amounting to some three hundred or more, 

 laid by the mother in batches on the surface of a pond or ditch, give rise to w r orm- 

 like larvae furnished with a distinct head, a large somewhat squared thorax, and a 

 tapering jointed abdomen. Along each side of the body there is a row of bristle- 

 tufts, one for each segment, and the last segment is in addition produced into a 

 couple of tubular tails, at the extremity of which open the trachea or breathing- 

 tubes. Thus equipped, the young gnat hangs suspended in the water, its heavy head 

 directed downwards, and the tip of its forked tail just projecting above the surface, 

 so that the apertures of its breathing-apparatus are in communication with the air. 

 Occasionally when the surface of the water is disturbed, or from any other reason 

 causing alarm, the larva wriggles to the bottom of the pond, soon, however, to return 

 to its accustomed place at the surface. During growth, the larva undergoes a series 

 of three moults before reaching its full size, the newly - clothed insect escaping 



BANDED GNAT. 



a, Female ; b, Larva ; c, Pupa. (All enlarged.) 



