434 



SCIENCE OF GARDENING. 



Part II. 



manifestator 



nera have an aculeus or sting, that lies concealed within the abdomen, which is used as 

 a weapon, and instils into the wound an acrid poison : those which want the sting are 

 furnished with an oviduct that is often serrated, and with which the eggs are deposited, 

 either in the bodies of the caterpillars of other insects, or in wood. From these eggs the 

 larva? are produced, which in some have no feet, in others more than sixteen. They 

 change to pup* incompletce, which are enclosed in cases. Some of the insects of this 

 order live in societies, others are solitary. 



O2.r,o The eall-flv (Cynips) pierces the leaves, &c. of plants with its sting, and deposits its eggs in the 

 wound the Ixtravasated juices rise round it, and form a gall (Jig. 407. a) which becomes hard ; and in this 

 the larva CM lives and feeds, and changes to a pupa (c, c), and afterwards to the imago, or perfect insect (d). 

 The C quercus fold {Jig- ^- d )> and - glechomatis, or ground-ivy gall-fly, are very common. 



2260. The saw-fly (Tenthredo), in the larva state 407 

 ( fig. 407. e), bears a strong resemblance to some of 

 the caterpillars of the lepidopterous insects ; but 

 is distinguishable by the number of the feet, 

 which are never fewer than sixteen, exclusive 

 of the thoracic pairs; the larva? feed on the leaves 

 of plants, and the pupa is enclosed m a strong 

 gummy case (/), retiring in the autumn, and the 

 perfect fly (g) emerges early in the ensuing spring 

 The serrated sting is used by the female in the 

 manner of a saw, to make incisions in the twigs, or 

 stems of plants, where it deposits its eggs. T. rosas 

 (fig- 407- e > f> g) is a common species. The T. gros- 

 sularia? (h) is also frequent in gardens : both are 

 very troublesome species of this genus. 



2261. The ichneumon is a very numerous genus, 

 there being upwards of 800 British species. The 

 eggs, in most kinds, are deposited in the bodies of 

 caterpillars or pupa?, which are there hatched : 

 the larva? have no feet ; they are soft and cylin- 

 drical, and feed on the substance of the caterpillar ; 

 this last continues to feed and even to undergo its 

 change into a chrysalis, but never turns to a per- 

 fect insect: when the larva? of the ichneumon 

 are full grown they issue forth, spin themselves 



a silky web, and change into a pupa incompleta, and in a few days the fly appears. 

 (fig. 407. i) is common in woods. 



2262. The bee (Apis), wasp (Vespa), and ant {Formica) are well known. All the species of ant are of 

 three sorts, male, female, "and neuter. The neuters alone labor ; they form the ant-hill, bring in the 

 provisions, feed the young, bring them to the air during the day, carry them back at night, defend them 

 against attacks, &c. The females are said to be retained merely for laying eggs, and as soon as that is 

 accomplished they are unmercifully discarded. The males and females perish with the first cold ; the 

 neuters lie torpid in their nest, and thus nature compensates them by duration, what it denies them in 

 intensity of enjoyment. 



2263. The diptera, or two-winged insects, have two wings, and behind or below them 

 two globular bodies, supported on slender pedicles, called halter es or poisers. At the 

 mouth they have a proboscis, sometimes contained in a vagina, and sometimes furnished 

 at its sides with two palpi, but no maxilla. Their eyes are reticulated and large. The 

 females, in general, lay eggs, but some are viviparous ; the larva; of the insects of this 

 order are as various in their appearance as the places in which they are bred. In general 

 they do not cast their skins, but change into a pupa state. Flies, strictly so called, gad- 

 flies, and gnats belong to this order. 



2264. Thegadjly ((Estrus) is a genus exceedingly 

 troublesome to horses, cattle, and sheep, in the skins 

 of which they deposit their eggs (fig. 408. a), which 

 soon change into larva?, that feed under the skin of 

 living animals (b), and often line the stomachs of 

 horses under the name of bots (Clarke, in Linn. 

 Trans, vol. iii.) ; the larva? are soft, smooth, annu- 

 late, without feet, and in most species furnished 

 with hook-like appendages : the chrysalis (c) differs 

 little in form from the larva?. The O. bovis (d) in- 

 fests oxen ; O. ha?morrhoidalis (e), horses; and O. 

 ovis, sheep. 



2265. The crane-fly (Tipula) resembles the gnat.it 

 feeds on various substances; the larva? are without 

 feet, soft and cylindrical; pupa cylindrical, horned ; 

 some species reside amongst the roots of aquatic vege- 

 tables, others amongst grass ; but by far the greater 

 number are aquatic. The perfect flies are found in 

 abundanceintheautumnalmonths. TheT. oleracea, 

 or long-legs, feeds on the roots of the cabbage; and 

 the T. crocata (fig. 409. a) and other species inhabit 

 meadows, and are common from spring to autumn. 

 The wheat-fly, T tritici (b), twelve of which have 

 been observed at one time, laying their eggs in a 

 single ear of wheat, would soon become of serious 

 injury to mankind, were not their race kept within 

 due bounds by several natural enemies, particularly the ichneumon tipula?. The well-known gaffer long- 

 legs, so frequently seen in houses in the autumnal evenings, flying about the flame of the candles and often 

 perishing in the blaze, is the T. rivosa (c), one of the larger species of the genus. The eggs of the wheat- 

 fly (d) are very small ; when magnified they appear roundish (e) ; the larva: also (/), and the perfect insect 

 (b), to be studied, should be magnified (g, h). 



408 



