The following brief summary of what takes place in the plant-louse of the rose (Aphis rosae), may be regarded as typical of the family, though exceptions occur in other species.
Lewisi 'in a' louse (Haematopinus) is, in its main features, similar.
That a wood-louse and a land-crab are alike Malacostracans, and that they have by different paths alike become adapted to terrestrial life, are facts which even a philosopher might condescend to notice.
Two species of Pediculus are found on the human body, and are known ordinarily as the head-louse (P. capitis) and the body-louse (P. vestimenti); P. capitis is found on the head, especially of children.
The irritation is caused by the rostrum of the insect being inserted into the skin, from which the blood is rapidly pumped up. A third human louse, known as the crab-louse (Phthirius pubis) is found amongst the hairs on other parts of the body, particularly those of the pubic region, but probably never on the head.
The name was first given in 1834 to a plant-louse which was observed to "dry up the leaves" of oaks in Provence.
- Book-louse (Atropos divinatoria, Fab.), Europe.
The louse of monkeys is now generally considered as forming a separate genus (Pedicinus), but the greater part of those infesting domestic and wild quadrupeds are mostly grouped in the large genus Haematopinus, and very rarely is the same species found on different kinds of animals.
Louse-infestation is known as phthiriasis in medical and veterinary terminology.
- Biting-louse E.
The following full description of the only species which attacks the vine, the Phylloxera vastatrix, or grape-louse, is reprinted from the article Vine in the 9th edition of this encyclopaedia.
"You see, dear man, this is not a sewing shop, and I had no proper tools; and, as they say, one needs a tool even to kill a louse," said Platon with one of his round smiles, obviously pleased with his work.