118 NATURAL HISTORY. 



furnished at the end with two rows of minute horny booklets, and enclosing a much finer protrusible 

 tube, probably representing the other parts of the mouth, and the whole is so completely retractile 

 that when not in use nothing can be seen of any part. 



These insects constitute a single family (Pediculidse), and are all parasitic upon various 

 Mammalia, each species being usually confined to some particular animal. They crawl about among 

 the hairs of their host, to which they readily cling by means of the clasping tarsi. They live upon the 

 blood which they suck from its tissues. The females attach their eggs to 

 the hairs near their insertion into the skin. In the case of the common 

 Louse of the human head, the young are hatched in about nine days, and 

 take about eighteen days to attain their full growth. The known species 

 are not very numerous, probably in part owing to the disagreeable associa- 

 tions attaching to the very name of these insects. Man is subject to the 

 ..^.^ attacks of three, if not four species, namely, Pediculus cajntis, inhabit- 

 PEDICULUS CAPITIS. * n S tne head; P. vestimenti, infesting the clothed surface of the body, 



and Pkthirius pubis, which is also a body Louse, but is confined to par- 

 ticular regions. The fourth species is the Pediculus tabescentium, which has been described as occa- 

 sionally appearing upon a patient in immense numbers, and producing a disease known to the 

 ancients as phthiriasis, and said to have been sometimes fatal. In all cases the best mode of 

 getting rid of such unwelcome guests is a thorough application of oil of turpentine or some other 

 essential oil. 



CHAPTER XIV. 



ORDER ORTHOPTERA. 



ORTHOPTERA Characters Structure Internal Structure Metamorphoses Distribution Classification THE OR- 

 THOPTERA GENUINA TKIBE SALTATORIA THE GRYLLID.E, OR CRICKETS The House Cricket The Field 

 Cricket The Mole Cricket THE LOCUSTID^E The Great Green Grasshopper THE ACRIDIID^E, OR GRASSHOPPERS 

 Locusts TRIBE CURSORIA THE MANTID^E Praying Insects Soothsayers THE PHASMID.E, OR WALKING STICKS 

 Walking Leaves THE BLATTID^E, OR COCKROACHES The Common Cockroach The Gigantic Cockroach, or " Drummer " 

 TRIBE EOPLEXOPTERA THE FORFICULID^E, OR EARWIGS THE PSEUDONEUROPTERA TRIBE SOCIALIA 

 THE TERMITID^E, OR WHITE ANTS TRIBE CORRODKNTIA THE EMBIID.E THE PSOCID.E TRIBE PLECOPTERA THE 

 PERLID.E The Stone Fly Pteronarcys TRIBE SUBULICORNIA THE EPHEMERID.E, OR DAY FLIES May Fly THE 

 LIBELLULID^E, OR DRAGON FLIES THE PHYSOPODA Thrips -THE MALLOPHAGA THE THYSANURA 

 Lepisma THE COLLEMBOLA Spring-tails Podura. 



THE Orthoptera, as already stated, include all the forms of insects with an imperfect metamor- 

 phosis and a biting mouth, of which the parts are exposed so as to be more or less recognisable 

 externally ; they have frequently appendages at the extremity of the abdomen, but these never 

 serve as locomotive organs, as is usually the case in the following order. The members of the order, 

 however, present so much diversity of character that there is but little to be said about the 

 group in general : in fact, it may be a question whether the differences presented by the various 

 subordinate types are not really in part of ordinal value ; indeed, some of them have actually been 

 formed into distinct orders by different entomologists. 



There is, however, one peculiarity characteristic of all but certain low and aberrant forms 

 of the order, namely, the division of the lower lip (labium}. This organ in the most typical forms 

 shows four, or in other cases two, distinct lobes in front, and the ligular part behind these is, oleft 

 in the middle, so that the precise equivalence of the labium to a second pair of maxillae is at once 

 apparent (see figure on p. 119); even when the parts are not so distinct as is here shown, there is 

 always an indication of the median cleft, showing that the labium is composed of a pair of maxilli- 

 form organs. In the Dragon Flies we find this structure somewhat masked, but it is still 

 recognisable by careful study ; and various modifications of the organ occur in other groups. The 

 maxillae generally have a distinct outer lobe, known as the galea (or helmet), from the mode in 

 which it overtops the inner biting lobe ; the maxillary palpi are usually well developed, and com- 

 posed of five, or even seven, joints. The eyes are usually of moderate or large size, but sometimes 

 represented by an aggregation of simple eyes on the sides of the head ; the ocelli are seldom wanting, 



