Ichneiimon-Fly.] 



MUSEUM OF ANIMATED NATURE. 



351 



dam to have the power of closing the anterior pair 

 by means of a valvular fold of skin, so that when it 

 is in the act of burrowing, all loose particles may be 

 prevented from entering the orifices. 



Fig. ;iJ472 represents this maggot and the perfect 

 fly : a, the maggot extended ; b, in an arched posi- 

 tion, preparing to spring ; c, the same more con- 

 tracted ; /and g, the fly, of the natural size ; e, the 

 fly magnified. 



There is a group of active predatory insects, 

 termed ichneumon-flies, to which we have already 

 alluded, many of which deposit their eggs in the 

 bodies of various caterpillars, othei-s in the cells 

 of certain bees and wasps. For this purpose the 

 females are furnished with a singular ovipositor, 

 often of considerable length ; it consists of a borer, 

 hard and sting-like, between two long blades, which 

 form its sheath. In many cases, perhaps in most, 

 the borer is serrated at the point, which is extremely 

 acute. 



Fig. ,'}473 shows a common species of ichneumon- 

 fly, Pimpla manifestator and its ovipositor : a, the 

 fly ; b, its ovipositor opened ; c c, a magnified view 

 of the ovipositor ; d, the serrated point of the borer. 

 This insect avails itself of the collection of cater- 

 pillars made by the mason-wasp for the support of 

 its own larva, and assaults the cell after it is blocked 

 up with tempered clay, havin? patiently waited till 

 the whole was completed. By means of her ovi- 

 positor she drills through the barricade of clay, and 

 then deeply inserting it, deposits her eggs in the 

 cell by means of the ovipositor, and which not only 

 prepares the way, but also conveys them to their 

 destined situation. Reaumur tells us that, having 

 made an artificial vespiary of sand and mortar upon 

 a wall, he perceived one of these ichneumons at the 

 instant it alighted on the spot under which so many 

 of the little green caterpillars had been stored up 

 by the wasps. Its long tail, or ovipositor, which 

 it carried horizontally, appeared to form but one 

 bristle, though really composed of three, and this 

 it raised, and lowered, and bent in various directions, 

 and soon applied it to the blocked-up entrance of 

 the nest, and worked it in the manner of a bradawl, 

 turning its body from right to left, and the contrary. 

 In this labour it persevered for a quarter of an hour 

 before it succeeded in penetrating to a suflicient 

 depth and reaching the coil of caterpillars, on which 

 its future larvae were to feed, to the destruction of 

 those of the wasp. 



Fig. 3474 shows the ichneumon-fly in the act of 

 depositing its eggs : a, an ichneumon-fly at rest ; 

 h b, its ovipositor; c, an ichneumon which has just 

 bored through the clay barricade of a mason-wasp's 

 nest, at e, into which her ovipositor, d, descends to 

 the roll of caterpillars, _/; where the egg is laid. 



Among the caterpillars which become the victims 

 of ichneumon-flies, that of the common cabbage- 

 butterfly (Pontia Brassicae) is about the most com- 

 mon. The fly which attacks this, the Microgaster 

 flomeratus, is of small size, black, with yellow legs. 

 larking its victim, it settles on it, and then deli- 

 berately plunges its ovipositor between the rings of 

 the caterpillar's body, and deposits an egg in the 

 wound; this done, it shifts its place, pierces again, 

 and deposits another egg, till twenty or thirty are 

 laid. "Though wounded in so many places, the 

 caterpillar seems to feel but little pain, and only 

 gives a slight twitch now and then, as if irritated, 

 nor does the body become swollen. In a little time 

 the eggs hatch ; in the meantime the caterpillar 

 eats, grows, and changes its skin as usual ; the living 

 parasites within subsist all the while on the living 

 body of the caterpillar, and strange to say, avoid 

 the vital organs, instinct-guided in their ravages. 

 In due time the caterpillar leaves the plants on 

 which it has fed, and creeps up walls or palings, as 

 if about to undergo its transformation. The parasite 

 JarvsB are at this crisis ready to emerge ; they eat 

 their way out, change immediately into the pupa 

 »tate, and envelop themselves in cocoons of bright 

 canary-coloured silk. Clusters of these little yellow 

 pupae may be seen in autumn on garden walls, and 

 often the withered empty skin of the dead caterpillar 

 in contact with them. 



Fig. 3475 represents : a a, the caterpillar of the 

 Pontia Brassicae ; b, the eggs of the butterfly glued 

 to the leaf ; c, the Microgaster glomeratus, magni- 

 fied ; d d d, the magnified view of a dissected cater- 

 pillar, in whose body a number of the larvae of the 

 ichneumon in question have been hatched ; e, the 

 silk cocoons spun by these larva; after their exit ; 

 /the larvae spinning their cocoons; g, the larvae 

 eating their way out of the body of the caterpillar. 

 But it is not only into caterpillars that ichneumon- 

 flies thus introduce their eggs ; there are certain 

 Tery minute species which absolutely deposit their 

 eggs within the eggs of other insects and spiders, 

 and upon these do the larvae subsist. Bonnet 

 assures us that he has had ocular demonstration 

 of the fact, and witnessed the evolution not of one, 

 but of a number of these minute parasites from the 

 egg of a butterfly. Others again deposit their eggs j 



in the bodies of perfect insects — the Aphides have 

 an enemy in the Microgaster aphidium. A very rare 

 species, the Evania apendigaster, which has been 

 occasionally found near London, selects that nui- 

 sance of our kitchens the cockroach (Blatta), as the 

 living depository of its eggs (see Fig. 3476, Evania 

 apendigaster, magnified) : while a still more rare 

 species, Stylops Melittae, first discovered by Mr. 

 Kirby, introduces its eggs into the body of the black- 

 bronze bee (Andrena nigrooenea), and perhaps other 

 species. (See Fig. 3477, the Stylops Meiittae, mag- 

 nified.) The species of an allied genus, Xenos, have 

 been discovered parasitic in wasps, by Professor 

 Peck, in America. Fig. 3478 represents a species 

 of ichneumon, in which the long ovipositor is 

 adapted for probing the nests of other insects. 



Let us pa-ss to other insects which bore into the 

 bark or substance on leaves of trees and plants, and 

 there form a nidus for their eggs ; instinct-guided 

 in the selection of the vegetable peculiarly suited 

 for the food of the future larvae : among these are 

 the Cicadae, or tree-hoppers,_the gall-flies (Cynips), 

 and others. 



- The tuneful Cicadae (which are not grasshoppers, 

 as the term is often most erroneously translated) 

 are common in the south of Europe, but not in the 

 more northern portions, and but one true Cicada, 

 we believe, is to be found in our island — the Cicada 

 haematodes, discovered by Mr. D. Bydder, in the 

 New Forest, Hampshire. 



These insects, which Virgil describes as rending 

 the bushes with their song, display the most inter- 

 esting and curious habits in the mode adopted for 

 securing their eggs. The female, which is mute, is 

 armed with an ovipositor, or, as Reaumur calls it, 

 an auger (tariere), by means of which she is enabled 

 to cut out long cells in the branches selected for the 

 reception of her eggs. 



The instrument is of a considerable size, and when 

 not in requisition is lodged in a sheath in a groove 

 of the last abdominal ring, from which it can be 

 protruded at pleasure. When examined with a 

 microscope, it is seen to consist of three portions — 

 a middle horny portion, spear-pointed at the apex, 

 and two horny sheath blades, with nine serrations 

 on each side' at the point, acting as a file or saw. 

 The stems of these two files are grooved along their 

 inner side, and each groove is fitted by a ridge of 

 the central borer, so that they both strengthen it, 

 and also slide up and down it, as moved by power- 

 ful muscles they rasp or saw the wood. The branch 

 chosen is either dead or very dry, and of such a size 

 that the excavation will extend to the pith, which 

 however is left untouched to form a bed lor the eggs. 

 These are very numerous, one female laying from 

 five to seven hundred, and are distributed in many 

 cells : the mouth of each excavation is protected 

 by the little fragments of wood detached during the 

 operation of boring. The larvae, when hatched, 

 issue forth out of the apertures, seek the ground, and 

 feed on the roots of plants, burrowing through the 

 hard soil. They are transformed not into torpid 

 pupae, but into active nymphs, remarkable for the 

 strength and size of their fore limbs, which are ad- 

 mirably adapted for digging. Fig. 3479 represents 

 the ovipositor of the tree-hopper magnified ; and 

 Fig. 3480, excavations in a small branch, with the 

 eggs in situ. 



The saw-flies (Tenthredo) also deposit their eggs 

 in grooves cut in the stems of twigs or branches, by 

 means of an ovipositor of curious construction. This 

 instrument is retracted within a narrow abdominal 

 slit, and when brought into view and examined by 

 means of a microscope, is found to unite in itself 

 the properties of a rasp and saw. There are two 

 fine and rigid blades with remarkable serrations, 

 having their backs lodged in a groove formed by two 

 membranous plates, which are thick and stout at the 

 base and narrow at the point ; these form a support 

 to the saws, which are worked up and down, by the 

 force of muscles acting upon them: besides the 

 saw-edge, these blades have rasping pectinations, 

 or comb-like teeth on the back of the instrument, 

 which is thus rendered more efficient. Fig. 3481 

 shows the ovipositor of a Tenthredo protruded from 

 its sheath, magnified. Fig. 3482 shows the ovipo- 

 sitor still more magnified: the comb-like rasps are 

 indicated by the cross-lines. Fig. 3483 shows a 

 portion of the saw, very highly magnified, with the 

 pectinations based upon the transverse lines. When 

 the saw-fly has fixed upon a branch as the recipient 

 of her eggs, she bends her body, protrudes her saw, 

 and works it so as to form a groove in the bark, and 

 in this deposits an egg, gluing it to its place by a 

 sort of frothy secretion ; then moving onwards, she 

 works out another groove, and places it in an egg, 

 as before, and in this way continues till all her eggs, 

 about twenty in number, are deposited. This occu- 

 pies her more than one day ; for Reaumur observed 

 that it took one of these flies ten hours and a half 

 in making six grooves in succession. The grooves 

 appear like small punctures with a lancet, which 

 become wider, with more elevated edges, as the egg 



increases, till the larva is hatched, and makes its 

 exit. One species of saw-fly, with deep violet wings 

 and a yellow body, and which selects the rose-tree 

 for her eggs, instead of depositing them separately 

 in distinct punctures, forms one long slit, and there 

 deposits them in two parallel rows, each in a little 

 cell-like depression. Fig. 3484 represents the eggs 

 thus arranged. 

 Of the ravages of the larvae of the saw-fly on the 

 : leaves of the gooseberry and currant trees especially 

 during certain years, the gardener can unfold a sad 

 j account. Thisinsect, the NematusRibesii, does not, 

 like other species, cut a groove in the branch in 

 which to deposit her eggs, but, according to Rdau- 

 mur— who introduced a pair of these flies under a 

 bell-glass, with a branch of a red-currant bush, in 

 order to watch their operations— the fly passes un- 

 der the leaf, and there deposits her eggs, six of 

 which were laid and secured to the leaf in the space 

 of a quarter of an hour ; but, as hi says, without 

 any perceptible groove being cut, notwithstanding 

 the possession of a saw. It is very probable, how- 

 ever, that a minute incision was made, which fitted 

 the egg closely, and applied glue to it, and which 

 might easily be overlooked. In about three weeks 

 the caterpillars are hatched, and feed together in 

 troops, often stripping the trees of every leaf ; whole 

 plantations of gooseberry and currant trees are fre- 

 quently devastated, all hope of fruit being de- 

 stroyed. The caterpillar is green mixed with yel- 

 low, and shagreened with minute, raised, black dots. 

 At its last change of skin these colours disappear, 

 and it becomes smooth, and yellowish white. It has 

 six legs and sixteen pro-legs. 



Among our British species of saw-fly there is one, 

 the Nematus Capreae, the caterpillars oif which are 

 exceedingly destructive to various kinds of willow, 

 sallow, and ozier ; entirely stripping off the leaves. 

 While feeding they assume singular attitudes and 

 cling by the fore feet. The fly makes its appear- 

 ance in spring; and the female deposits her eggs in 

 a round patch on the back of the leaf, but not on 

 the nervures, as does the saw-fly of the gooseberry, 

 which it very closely resembles. Another species, 

 of large size, infests the alder (Alnus glutinosa) ; it 

 is the Selandria Alni of Stephens : the caterpillar is 

 very voracious. 



In North America, a species of saw-fly, Tenthredo 

 Cerasi, is most destructive to various fruit-trees — as 

 the cherry, plum, pear, and quince — and has of late 

 years so increased as to produce serious alarm in 

 some districts. The caterpillar is called the slug- 

 worm ; and when numbers are collected together, 

 they exhale a most unpleasant odour. The history 

 of this caterpillar, and its devastations, is written by 

 Professor Peck ('Nat. Hist, of Slug-worm,' Boston. 

 1799). 



Fig. 3485 represents the saw-fly of the goose- 

 berry — Nematus Ribesii — a a a ; on the leaf b its 

 eggs are shown, adhering to the nervures; d d, the 

 caterpillars eating ; c, one rolled up ; /, one ex- 

 tended. 



Fig. 3486 represents at a the caterpillars of 

 Nematus Capreae, on the ozier ; b, those of Selandria 

 Alni, on the alder. 



It may have suggested itself to our reader, that 

 excepting as it respects use, there is great affinity 

 between the sting of the bee or vvasp and these keen 

 ovipositors, which we have noticed in the ichneu- 

 mons and saw-flies; and such is really the case, and 

 as its details will be perhaps better understood by 

 being compared with the ovipositors mentioned, we 

 may here say a few words respecting it. 



The sting of the bee is really a formidable in- 

 strument, and so extremely acute, that a good glass 

 will not render the extreme point visible, as it will 

 that of a needle. It consists of an extensile sheath, 

 enclosing two needle-shaped darts much finer than 

 a human hair, and scarcely to be distinguished by 

 the naked eye ; these with the sheath together form 

 the sting, and the whole of the parts are numerously 

 barbed at the point ; hence when plunged into the 

 skin, the bees can seldom withdraw them, and they 

 are consequently wrenched out of the insect's body, 

 most probably to its speedy destruction : the sting 

 is moved by powerful muscles, eight in number, 

 according to Swammerdam, which by their action 

 protrude from its recess and urge into the skin ; it 

 appears that each part of the sting is capable of 

 separate movement. On more than one occasion, 

 when the .sting of a wasp, the point of which has 

 been just forced into the skin, has with the whole 

 apparatus been torn from the insect's body, have we 

 seen the muscles continue their movements, and 

 that for a considerable time. Was the sting of a 

 wasp or bee a simple sharp weapon, it would give 

 not so much pain as the puncture of a needle, but, 

 as we well know, it produces very great pain and 

 inflammation ; this pain is owing to a poison which 

 the sting distils into the wound, and which is se- 

 creted in a large sac attached to the base of the 

 weapon, and communicating with it by means of a 

 fine tube, through which the poison flows. The s ic 



