3 68 LAKES AND STREAMS 



five weeks, the enormous number of gnats in existence being easily accounted for, 

 since from four to six generations may be produced in a single season. Gnats form 

 the favourite food of many birds, especially swallows, but they are most trouble- 

 some to mammals, sucking the blood and pursuing their victims day and night, 

 most probably being attracted by the odour of perspiration which emanates from 

 the body; they live also on the juices of plants and other liquids, and in many 

 cases die without having once tasted blood at all, this being especially the case 

 with the males, which bite but seldom. The females, on the other hand, produce 

 painful inflammation by leaving their bite, although they are not the vehicle by 

 which the parasite of malaria is introduced, this being carried by gnats or 

 mosquitoes of the allied genus Anopheles, one of which inhabits the Roman 

 Campagna. 



Stagnant waters often assume a red appearance from the worm- 

 ' shaped larvae of the plumed midge (Chironomus pl^mosus), which 

 belongs to the family of the twitching gnats, so-called because of the convulsive 

 motion of the long front-legs while the insect is at rest. The plumed midge has a 

 pale green thorax with grey streaks on the back of the body, which is dusky 

 brown, while there are lighter ridges and black specks on the centre of the foremost 

 edge of the white wings : the length is about five-eighths of an inch. The bearded 

 midges which belong to the same family also live in water during the larval state, 

 and are found among bushes : their bite is very painful. To this group belong also 

 the black midges (Ceratopogon pulicarius), which often attack the natives of 

 Lapland in legions, creeping into the mouth and nose, from which it is almost 

 impossible to expel them. 



Still greater torments are the sand-flies (Simuliidce). the larvae of 

 Sand Fly, etc. ... . . . 



which live in water under bag-like cells, and are especially abundant 



in stagnant pools. These minute flies creep into the nose, mouth, and ears 

 of cattle, when the bite is so painful as in some cases to cause death. The crawling 

 sand-fly (Simulia reptans), so frequently met with in spring in continental 

 woods, is particularly troublesome, as it generally bites on the most sensitive parts 

 of the face, i.e. near the nostrils. In length an eighth of an inch or less, it has white 

 rims to the dark blue thorax, the back is brown shading to black, the legs are 

 brown with white shields, and the front joints of the fore-legs dark black. One of 

 the worst of this group of flies is the Columbatsch fly (S. columbatzensis), taking its 

 name from a village in Servia on the right bank of the Danube, where it abounds. 

 About an eighth of an inch long, and ash-grey in colour, with two broad dusky 

 stripes on the ridge of the breast, divided by a fine line, and black spots on the 

 hind part of the body, this fly makes its appearance in Servia in April and May, 

 and again in August in cloud-like masses in the vicinity of woods and water, attack- 

 ing man and beast, very often entirely covering the body, and causing by its bite 

 inflammation, fever, and convulsions, sometimes resulting in death, in consequence 

 of the swelling which the bite produces. In 1783, in the Banat district, fifty-three 

 horses, one hundred and thirty -one head of cattle, and three hundred and sixteen 

 sheep were killed by this insect ; in the year 1830, on the banks of the River March, 

 several hundred horses and cattle died from the same cause; and in 1785 an 

 immense multitude were driven by a storm from Servia into Transylvania, where 



