TERZI

This article appears in Volume V13, Page 262 of the Encyclopedia Britannica.

Encyclopedia Britannica - Main :: TAV-THE

TERZI . -_.
After Howard, Year Book U.S. Dept. Agr., 1894.
into a process or hood-like structure which may extend far behind the tail-end of the abdomen. Two other allied families, the Cercopidae and Jassidae, are more numerously represented in our islands. The

young

of many of these insects are green and soft-skinned, protecting themselves
by the well-known frothy secretion that is called " cuckoo-spit."
In all the above-mentioned families of Homoptera there are three segments in each foot. The remaining four families have feet with only two seg-
Pmm Osborn (after Deane), meets. hey are of
B:dl. 5 (N.S.), Div. Ent. very

great

GREAT

zoological
G.S. Dept. Agr.

interest

INTEREST

on account of
( Pediculus vestimenti). their life-historypar-
Magnified. thenogenesis being of
normal occurrence among most of them. The families Psyllidae or " jumpers ") with eight or ten segments in the feeler and the Aleyrodidae (or " snowy flies ") distinguished by their white mealy wings, are of comparatively slight importance. The two families to which

special

SPECIAL

attention has been paid are the Aphidae or plant-lice (" green fly ") and the Coccidae or scale-insects. The aphids (fig. II) have feelers with seven or
fewer distinct segments, and the fifth abdominal From Osborn (after segment usually carries a pair of tubular pro- Schiodte), Ball., (IV .S.), cesses through which a waxy secretion is dis- Div. Ent. U.S. Dept. charged. Tha sweet " honey-dew," often Agr. .
sought as a food by ants, is secreted from the FIG. 15. Pro-intestines of aphids. The peculiar life-cycle in boscis of Pediculus. which successive generations are produced Highly magnified. through the summer months by virgin females
the egg developing within the

body

BODY

of the motheris de-scribed at length in the articles APHIDES and PHYLLOXERA. The Coccidae have only a single claw to the foot; the males (fig. 12 a) have the fore-wings developed and the hind-wings greatly reduced, while in the female wings are totally absent and the

body

BODY

undergoes marked degradation (figs. 12, e, 13, a, b). In the Coccids the forma-
tion of a protective waxy secretionpresent in many genera of Homopterareaches its most extreme development. in some coccids the " mealy-bugs " (Dactylopius, &c.) for examplethe secretion forms a white

thread

THREAD (0. Eng. praed, literally, that which is twisted, prawan, to twist, to throw, cf. " throwster," a silk-winder, Ger. drehen, to twist, turn, Du. draad, Ger. Draht, thread, wire)

-like or

plate

PLATE

-like covering which the

insect

INSECT

carries about. But in most members of the family, the secretion, united with cast cuticles and excrement, forms a firm " scale," closely attached by its edges to the surface of the plant on which the

insect

INSECT

lives, and serving as a shield beneath which the female coccid, with her eggs (fig. 13 a' and brood, finds shelter. The male coccid passes through a passive stage (fig. 4) before attaining the perfect condition. Many scale-insects are among the most serious of pests, but various species have been utilized by man for the production of wax (lac) and red dye (cochineal). See ECONOMIC ENTOMOLOGY, SCALE-INSECT.
ANOPLURA
The Anoplura or lice (see LOUSE) are wingless parasitic insects (fig. 14) forming an order distinct from the Hemiptera, their sucking and piercing mouth-organs being apparently formed on quite a different plan from those of the Heteroptera and Homoptera. In front of the head is a short tube armed with strong recurved hooks which can be fixed into the skin of the host, and from the tube an elongate more slender tucking-trunk can be protruded (fig. 15). Each foot is provided with a single strong claw which, opposed to a process on the shin, serves to grasp a

hair

HAIR (a word common to Teutonic languages)

of the host, all the lice being parasites on different mammals. Although G. Enderlein has recently shown that the jaws of the Hemiptera can be recognized in a reduced condition in connexion with the louse's proboscis, the modification is so excessive that the group certainly deserves ordinal separation.

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