OF NATURAL HISTORY. 97 



caterpillars of this genus are commonly found in (lagnant waters. 

 The gnats generally frequent woods and marfhy places. The fe- 

 males, in particular, are very troublefome, and fting feverely. — The 

 feet of the hippobofca, or horfe-jiy, are armed with a number of nails 

 or crotchets. In fome fpecies, the wings crofs each other; in others, 

 they are open. The horfe-fiies frequent woods and marfhy grounds, 

 and are extremely incommodious to birds and quadrupeds, whofe 

 blood is the only food of thefe infers. 



T\\& feventh order of infe6ls Linnaeus denominates aptera, becaufe 

 neither males nor females are furnifhed with wings. This order 

 comprehends thirteen genera, and a great number of fpecies, many 

 of which are very offenfive and noxious to the human fpecies. The 

 pediculus^ or loufe^ has fix legs, two prominent eyes, and its mouth 

 contains a fting or fucker, by which it extradts blood and other 

 juices from the bodies of animals. Though almoft every different 

 animal is infefted with a peculiar fpecies of lice, the fpecific charac- 

 ters of very few of them have hitherto been afcertained. Lice are 

 of various forms. Some of them are oval, others oblong, and others 

 long and flender. They are oviparous animals, and their eggs 

 are large in proportion to the fize of their bodies. Before they ar- 

 rive at maturity, they change their fkin feveral times. They are 

 fuppofed to be hermaphrodites. This circumftance, if true, may 

 partly account for their prodigious multiplication. Swammerdam 

 who diffeded a great number, afiures us, that he never found one 

 without an ovary, nor ever difcovered the organs peculiar to the 

 male fex. If this ftruflurc be univerfal, the loufe is an hermaphro- 

 dite of a very peculiar kind ; becaufe it muft be capable of foecun- 

 dating itfelf. Several fpecies of worms are hermaphrodites; but, 

 inftead of foecundating themfelves, they are obliged to impregnate 

 each other, — The pulex^ orjiea, has likewife fix legs, the articula- 

 tions of which are fo exceedingly elaftic, that the animal is enabled 

 t N • by 



