IGNIS FATUUS. 



IMPLEMENTS. 



to single out the larva or pupa of some parti- ' to their destruction. The cause of the pheno- 

 cular kind of caterpillar or other insect, to menon does not seem to be perfectly under- 

 which it therefore stands in the relation of stood ; it is, however, generally supposed to be 

 parasite. The eggs hatch in due time, and the produced by the combustion of some highly 

 larva of the ichneumon commences feeding inflammable gas, such as phosphorated hydro- 

 upon its victim, the vitals of which are soon ; gen, which takes fire spontaneously on rising 

 destroyed, after which the parasite or ichneu- j and mingling with atmospheric air 

 mon comes forth in due time to another state 

 of existence. 



Some of the ichneumon flies are extremely 

 small, and confine their attacks to the eggs of 

 other insects, which they puncture, and the 

 little creatures produced from the latter find a 

 sufficient quantity of food to supply all their 

 wants within the larger eggs they occupy. The 

 ruby-tails and cuckoo-bees lay their eggs in the 

 provisional nests 'of other insects, whose young 

 are robbed of their food by the earlier hatched 

 intruders, and are consequently starved to 

 death. The obligations which the farmer and 

 society at large owe to certain parasite insects 

 is forcibly illustrated in the case of the Hessian 

 fly, the devastations of which are often prevent- 

 ed through the destruction, during a single 

 season, of nearly a whole race by its parasite. 



Professor Peck has described a minute ich- 

 neumon fly, stated by Mr. Westwood to be a 

 species of Encyrtus, that stings the eggs of the 

 slug-fly, and deposits in each one a single egg of 

 her own. From this in due time a little maggot 

 is hatched, which lives in the shell of the slug- 

 fly's egg, devours the contents, and afterwards 

 is changed to a chrysalis, and then to a fly like 

 its parent. Professor Peck found that great 

 numbers of the eggs of the slug-fly, especially 

 of the second hatch, were rendered abortive by 

 this atom of existence. 



In treating of the pigeon tremex (Tremex co- 

 lumba'), which in its larva state is a destructive 

 tree-borer, Dr. Harris observes that it is often 

 destroyed by two kinds of ichneumon-flies, 

 (Pimpla atrata and /wnatorof Fabricius), which 

 may be frequently seen thrusting their slender 

 borers, measuring from three to four inches in 

 length, into the trunks of trees inhabited by the 

 grubs of the tremex and by other wood-eating 

 insects ; and, like the female tremex, they some- 

 times become fastened to the trees, and die with- 

 out being able to draw their borers out again. 

 The ichneumon flies are little busy-bodies, 

 ever on the alert, and with untiring scrutiny 

 continually prying into every place to find the 

 lurking caterpillar, grub, or maggot, wherein 

 to thrust their eggs. (Earns.) 



A specimen of this extensive family is re- 

 presented in PI. 15, fig. 12, in the Trogux /Wr?/s 

 which commits great havoc among caterpillars 

 and grubs. See APHIDIAXS, &c. 



IGNIS FATUUS (Lat. vain or foolish fire 

 a translation of the French feu folle!.) A kinc 

 of luminous meteor, which flits about in the 

 air a little above the surface of the earth, and 

 appears chiefly in marshy places, or near stag 

 nant waters, or in churchyards, during the 

 nights of summer. There are, we are told, 

 many instances of travellers having been de- 

 coyed by these lights into marshy places, where 

 they have perished ; and hence the names Jack- 

 with-a-luntern, Will-iciih-a-wisp; the common peo- 

 ple ascribing ihe appearance to the agency of 

 evil spirits, who take this mode of alluring men 



Milton, in his Paradise Lost, b. ix. 1. 634, thus 

 alludes to it: 



A wandering fire, 



Compact of unctuous vapour, which Ihe night 

 Condenses, and the cold environs round, 

 Kindled through agitation to a flame, 

 Which oft, they say, some evil spirit attends, 

 Hovering and blazing with delusive light, 

 Misleads the ama/ed nisiht wanderer from his way 

 To bogs and mires, and oft through pond <>r pool, 

 There swallowed up and lost, from succour far. 



IGNITION (Lat. ignis, fire). The act of 

 setting fire to, or of taking fire, as opposed to 

 combustion, or burning, which is a conse- 

 quence of ignition. The term "spontaneous 

 gnition" is applied to cases in which sub- 

 Stances take fire without previous application 

 f heat. This is illustrated in the burning of 

 lay-stacks, when the hay has been put up too 

 reen ; the scorching of corn-stacks from the 

 same cause, and the taking fire of ships laden 



with fermentable products. 



IMBRICATED. In botany, a term used in 

 speaking of the arrangement of bodies, to de- 

 note that their parts lie partly over each other 

 n regular order, like the tiles upon the roof 

 of a house, as the scales upon the cup of some 

 acorns ; also applied in speaking of the aesti- 

 vation of petals or leaves, to denote that they 

 overlap each other at the margin without, any 

 involution. (Brande's Diet, of Science.") 



IMPLEMENTS, AGRICULTURAL. Almost 

 all the operations of agriculture may be per- 

 formed by the plough, the harrow, the scythe, 

 and the flail ; and these, or similar tools for 

 performing the same work, are the sole imple- 

 ments in the primitive agriculture of all coun- 

 tries. With the progress of improvement, how- 

 ever, many other implements have been intro- 

 duced, the more remarkable of which are the 

 drill-plough, the horse-hoe, the winnowing ma- 

 chine, the thrashing machine, and the reaping 

 machine. The object of all these implements 

 and machines is to abridge human labour, and 

 to perform the different operations to which 

 they are applied with a greater degree of ra- 

 pidity, and in a more perfect manner than be- 

 fore. In the present work the different imple- 

 ments are treated of in their alphabetical order. 

 Of the progress made in the construction of 

 agricultural instruments in England, the judges 

 of implements at the Liverpool meeting of the 

 English Agricultural Society, in their report 

 very justly remark, when speaking of "the 

 good effects which have already resulted from 

 the public exhibition of implements at the So- 

 ciety's meetings, in stimulating the talent of 

 the mechanic and the zeal of the husbandman. 

 At Oxford the show-yard may be said to have 

 presented an epitome of the state of agricultu- 

 ral mechanism existing in 1839, the era of the 

 formation of the Royal Agricultural Society of 

 England. No spectator of that show can have 

 failed to be struck with surprise and admira- 

 tion at the Liverpool exhibition. At Oxford 

 there were some examples of good machinery 



