THE MALLOPHAGA. 147 



closely resemble in general form and structure, differing chiefly (besides the want of wings in those of 

 the -winded species) in "reater softness of the skin, in the shortness of the antennae, and in having 

 agglomerated instead of compound eyes. In the last, or nymph stage, the wings are usually seen in 

 their cases but the antennae are turned back upon the head. There is a filmy integument about 

 the joints of the limbs, and the insect is more sluggish than in the larva or perfect state. 



Although the mouth, as we have seen, is constructed upon a maiidibulate type, the insects appear 

 to use it for suctorial purposes, although the precise mechanism by which it acts does not seem 

 to have been made out. There are two principal groups or families of these insects, in one of which, 

 the TUBULIFERA, the last segment of the abdomen in both sexes forms a little tube ; while in 

 the other, the TEREBRAXTIA, the females are provided with a regular ovipositor composed of foui 

 minute valves concealed in a groove of the last two ventral segments. In the former the antennae are 

 eight-jointed ; the latter usually have nine-jointed antennae, and they possess the power of jumping 

 by the a^encv of the abdomen. These insects are generally known to gardeners by the name of the 

 Thrip or Thrips, the latter being the name of the most typical genus. Some of them occasionally 

 prove injurious to cultivated plants. This is especially the case with the Corn Thrips (Thni>a 

 cerealium), which generally attacks the ears of corn, and when numerous may be mischievous. 



SUB-ORDER IV. MALLOPHAGA. 



These insects may be denominated " mandibulate lice," that is to say, both in appearance and 

 general habits they somewhat resemble the true Lica, with which they were formerly arranged, but 

 differ in the possession of biting mouths, and in the diet to which such a structure adapts them. 

 They are small flat insects, with the upper surface more or less horny in its texture ; the head is 

 broad and horizontal ; the thorax narro f? and destitute of all traces of wings ; the abdomen usually 

 broad and of nine or ten segments ; and the legs short and stout, with tarsi of two joints furnished 

 with one or two claws. The eyes are small and usually simple ; the antennae consist of from three 

 to five joints; and the mouth, which is situated beneath the head, contains a pair of short hooked 

 mandibles, a pair of small maxillae with or without palpi, and a labium with palpi of two joints. 



A great number of these curious little insects have been recorded, and they inhabit all parts 

 of the world, in fact it would seem as if there were few birds at any rate to which no parasite 

 of this group is attached. They live among the hairs of 

 the Mammalia and the feathers of birds, each species of 

 parasite being usually attached particularly to some species 

 or small group of species of these warm-blooded Vertebrates ; 

 but unlike the true Lice they do not feed upon the blood 

 of their hosts, but upon the finer hairs and downy feathers. 

 Frequently they occur in considerable numbers, and may then 

 perhaps, to some extent, be injurious. 



Here again two principal families may be distinguished. 

 The PHILOPTERID.E have thread-shaped antennae of three or PHILOPTERVS SELCIFEONS. 



five joints, and no maxillary palpi. The species with five- 

 jointed antennae (Philopterus, Xii-mus, Docophonis, &c.) infest birds; and those with the antennae of 

 three joints (Trichodectes, &c.) are found upon mammals of various groups. In the second family 

 (LIOTHEID.E) the antennae are clubbed and composed of four joints, and the maxillary palpi are present. 

 Species with distinct labial palpi, and two claws on each tarsus (Liotheum, and allied genera), live 

 upon birds ; and those with no labial palpi, and with only one claw on each tarsus, on mammals. The 

 common fowl, clucks and geese, game-birds of all kinds, and pigeons are very commonly infested 

 by these parasites, as are also the dog and cat, the sheep and the guinea-pig. 



ORDER THYSANURA. 



We have now reached the last order referred to the class of true insects, and it is a group 

 of no small interest from a philosophical point of view. The forms composing it are reckoned to 

 present the nearest resemblance to the theoretical progenitors of the Insecta in fact, Sir John 

 Lubbock hints that they might well be regarded, not as insects at all, but rather as the surviving 



