INSECTS. 173 



Family : MusoaBformes {Gnat Flies). 



Gnats with relatively short legs, and antennae 

 which are in any case shorter than the body, and 

 are usually quite short and cylindrical, possessing, 

 however, six or more joints, while the antennae of 

 true flies usually have only three joints. The gnat 

 flies form, as it were, the transition between the 

 slender gnats with their long legs and antennae, and 

 the more thickset flies, the legs and antennae of 

 which are short. Here belong the genera of Shade 

 Gnats {Sciara, e.g. Sciara Thomas, the larvae of which 

 often wander about in companies, as the so-called 

 Army Worm), the Sand Flies {Sitnulia), and the Hair 

 Gnats [Bibio, e.g. the Garden Hair Gnat, Bihio hortu- 

 lanus, the larva of which gnaws the roots of plants, 

 especially in humous garden soil). 



The Sand Flies, or Mosqiiitoes (Simulia), 



have thick-set bodies, short legs, and short nine or ten- 

 jointed antennae ; they are from ^^ to ^ of an inch 

 long, and have a short but sharp proboscis, with which 

 they suck up the flower juices which constitute their 

 chief food. But the female also sucks the blood of 

 human beings and animals, making herself exceed- 

 ingly annoying in this way. Its larval state is passed 

 through in stagnant water ; its appearance is there- 

 fore local, and is especially favoured by damp 

 summers. The mature sand flies are found from 

 early spring or through the whole summer ; several 

 generations succeed one another in the same year. 

 Sand flies often appear in swarms, containing thousands 

 of individuals. Since the female eagerly creeps into 

 the ears, noses, and corners of the eyes in horses and 

 oxen, she is extremely annoying and even dangerous. 

 Her bite produces a smarting sensation, and may 

 cause actual boils to form in the skin. When a large 



