107 



IANTHINA. 



ICHNEUMON. 



193 



TANTHINA. [JAXTHKODJE.] 

 1 IBACUS. [SCVLLAKIANS.] 



IBALIA. [GALLICOL.E.] 



IBE'KIS, a genus of Plants belonging to the natural order Cntciferce. 

 It consists of annual, perennial, and slightly shrubby species, chiefly 

 inhabiting Europe, and particularly the northern shores of the 

 Mediterranean Sea. It has the pouch ovate or roundish notched ; 

 valves boat-shaped, winged at the back ; seeds one in each cell ; petals 

 unequal, two outer ones largest ; filaments simple. Two are found 

 in the north of Europe, one of which, /. amara, is British. The 

 species are remarkable, among other things, for their flowers growing 

 in close corymbs, and being much more developed on one side than 

 the other, next the circumference of the corymb. This irregularity, 

 connected with either a pure white or a rich purple of varying tints, 

 gives the plants a strikingly beautiful appearance; and hence they 

 are in many cases cultivated in gardens as objects of ornament, under 

 the name of Candy-Tuft, in allusion doubtless to their having been 

 first procured from Candia. I. Kmpervirens and /. Gibraltarica are 

 particularly well-suited for beautifying rock-work. 



IBERITE, a Mineral, allied to Giyantholite. [GIGANTHOLITE.] 



IBEX. [CAPBEJS.] 



IBIS. [ABOU-HANNES ; TANTALUM.] 



IBLA. [ClBBIPEDIA.] 



IBYCTER. [FALCOHID.E.] 



ICELAND-MOSS. , [CETBABIA.] 



ICELAND-SPAR. [CALCABEOCS SPAB.] 



ICE-PLANT. [MESEMBBVANTHEMOM.] 



ICE-SPAR. Transparent Crystals of 1'eltpar, Anorthite, and Ryaco- 

 lite are called by this name. 



ICHNEUMON. [HERPESTES.] 



I< HNEUMON, a genus of Insects belonging to the order Hymen- 

 optera, section Terebrcmtia, and family Pupivora, in the arrangement 

 of Latreille. The genus, as defined by Linnaeus, included such 

 pupivorous Uymenoptera as are furnished with veined wings (the 

 anterior pair presenting in their disc several complete or closed cells), 

 filiform or setaceous vibratile antennae composed of a great number 

 of articulations, and an ovipositor of various length and complicated 

 structure. The Linmean genus now constitutes a group including a 

 great many well-marked genera and an immense assemblage of species. 

 All these are remarkable for the habits of their larva;, which are 

 parasitic in the bodies of other insects. These bodies the perfect 

 Ichneumons perforate by means of their ovipositors, and there lay 

 their eggs. This destructive habit gave rise to the name by which 

 they are known ; a comparison being drawn between them and the 

 Egyptian Ichneumon (Berpestes Ichneumon) [HEBPESTES], the quad- 

 ruped celebrated as the destroyer of serpents and crocodiles. 



The history of these insects has attracted much attention among 

 naturalists, and many elaborate memoirs have been written upon 

 them. The purpose they serve in the economy of nature has been 

 well described by Kirby aud Spence : " The great body of the 

 ichneumon tribe is principally employed in keeping within their 

 proper limits the infinite host of lepidopterous larvae, destroying, 

 however, many insects of other orders. Such is the activity and 

 address of the Ichneumonidce that scarcely any concealment, except 

 perhaps the waters, can secure their prey from them ; and neither 

 bulk, courage, nor ferocity avail to terrify them from effecting their 

 purpose. They attack the ruthless spider in his toils ; they discover 

 the retreat of the little bee that for safety bores into timber, and 

 though its enemy ichneumon cannot enter its cell, by means of her 

 long ovipositor she reaches the helpless grub, which its parent vainly 

 thought secured from every foe, and deposits in it an egg which 

 produces a larva that destroys it. In vain does the destructive 

 Cecidomya of the wheat conceal its larva; within the glumes that so 

 closely cover the grain ; three species of these minute benefactors of 

 our race, sent in mercy by Heaven, know how to introduce their eggs 

 into them, thus preventing the mischief they would otherwise 

 occasion, and saving mankind from the horrors of famine. In Vain 

 also the C'ynipt, by its magic touch, produces the curious excrescences 

 on various trees and plants, called galls, for the nutriment and defence 

 of its progeny ; the parasite species attached to it discovers its secret 

 chamber, pierces its wall, however thick, and commits the destroying 

 egg to its offspring. Even the clover weevil is not safe within the 

 legumen of that plant ; nor the wireworm in the earth from their 

 ichneumonidian foes." (' Introduction to Entomology,' vol. i. p. 267.) 



The development of these parasites within the bodies of other insects 

 was for a long time a source of much speculation among early philo- 

 sophers, who fancied that occasionally one animal had the power of 

 becoming transformed into another. The eggs of the genus Op/lion 

 are of a singular form, being somewhat bean-shaped and attached 

 near one end to a long slender and curved peduncle, by which they 

 are attached to the body of the victim. The larva itself, when 

 hatched, retains this position, and thus lives upon the juices of the 



insect it attacks. The larva; which reside like intestinal worms within 

 the bodies of caterpillars, as the Microgasters, which infest the cater- 

 pillars of the white butterfly, carefully avoid touching the vital organs 

 of the creature they inhabit, living only upon the fatty matter until 

 they attain their full sizo and are ready to assume the pupa state, 

 when they pierce the skin of the caterpillar (which soon dies), spin for 

 themselves cocoons beneath its body, and undergo their transforma- 

 tions. The larva; of the majority of these insects spin a silken 

 cocoon, in which they undergo the pupa state. In some cases this 

 is rendered unnecessary by their peculiar habits, as for instance, the 

 Aphidii, which undergo their transformations within the indurated 

 skin of the Aphis, of which they have devoured the interior. 



The perfect insects are found flying amongst trees and plants, and 

 especially frequenting the heads of umbelliferous flowers, whence 

 they derive a great portion of their nourishment. Some species 

 whose females are furnished with a very long ovipositor are found 

 on the trunks of trees, stumps of wood, &c., evidently searching for 

 wood-eating larva;, in which they deposit their eggs ; whereas those 

 which have short ovipositors, seek external-feeding larvaj for the 

 same purpose. When taken in the fingers they immediately dis- 

 engage their terebra from the sheath aud attempt to sting, causing a 

 slight irritation for the moment, but so trifling is it that it ia evident 

 no very powerful poison can be introduced into the wound. They 

 fly very rapidly. M. Wesmael has described a remarkable gynandro- 

 morphous specimen, having the head and thorax with the organs 

 attached thereto of the female sex, while the abdomen and its 

 appendages are masculine. In the last Linnaean edition of the 

 'Systema Naturae,' 77 species were described as belonging to the 

 genus Ichneumon. 



Modern naturalists have elevated the genus Ichneumon into a 

 family Ichneumonidcc, which is again divided into two sub-families 

 Genuince and Adtntce. The former comprises the largest species 

 of the family, and is not only distinguished by having two recurrent 

 nerves, but also by having the nerve which separates the first cubital 

 or submarginal cell from the external diacoidal cell, either entirely or 

 nearly obliterated, whereby these two cells become confluent. No 

 genuine Ichneumon has yet been described in which this structure 

 does not exist. Moreover the second cubital or submarginal cell (the 

 area specularis of Fallen) is very greatly reduced in size, being some- 

 times petiolated, but often entirely obsolete. It is in this minute 

 area, or in the space which it should typically occupy, that the 

 second recurrent nerve is inserted. M. Wesmael also adds the 

 existence of an articulation between the second and third dorsal 

 segments of the abdomen. 



Amongst the Ichneumonida! may be noticed the genera Pimplct, 

 in which the ovipositor and its sheaths are often greatly elongated, 

 being in some exotic species 3 or 4 inches long ; Ophion, having 

 the abdomen greatly compressed and sabreshaped ; Euceroi and 

 Joppa having the antenna; dilated in the middle (of the former 



.genus males only have been observed) ; and Hellimgia, having the 

 antenna; strongly clavate at the extremity in both sexes. The in- 

 teresting genus Agnotypia is remarkable for its long curved petiole 

 to the abdomen, spotted wings, and spined scutellutn ; the radial 

 cell is short, whence, as well as in the form of the abdomen, it 

 appeared to Latreille to form the connecting link between the 

 Iclmeumonidce and Proctotrupidte. Its palpi and the cubital cell of 

 the fore wings however evidently prove its affinity with the true 

 Ichneumonidce ; although Mr. Halliday, on account of the want of 

 articulation between the second and third dorsal segments of the 

 abdomen, has formed it into a distinct family ; but this latter character 

 is proved by such genera as Chelonui, Sigalphus, &c., to be but of 

 secondary importance amongst the Ichncumonidce. 



Jchneumonides Adsciti, or Braconides, are characterised by having 



1 only one recurrent nerve, which unites with the nerve almost always 

 present, extending between the first cubital and externo-discoidal 



cells ; the second submargiual cell being often as large as the preceding, 

 and not receiving a recurrent nerve ; aud the non-existence of articula- 

 tion between the second and third dorsal segments of the abdomen. 

 In Agathis and some Microdi aud Microctoni the nerve between 



I the first cubital -and externo-discoidal cell is obliterated, as in the 



' genuine Iclmeumon. M. Weamael divides this sub-family as follows : 

 * Endodontes. Having the teeth of the mandibles directed 

 inwardly; the mandibles meeting together when shut. Divisible 

 into 



1. Polymorphi.Clypeus entire; abdomen 6-7-jomted ; posterior part 

 of the vertex convex, second submarginal cell (when present) large. 



2. Cryptogattri. Clypeus entire, posterior part of the vertex convex; 

 abdomen dorsally presenting not more than two transverse sections ; 

 second submarginal cell (when present) large. 



3. Arcolarii. Clypeus entire; vertex more or less emarginate 

 behind ; abdomen 6-7-jomted ; second submarginal cell (when present) 



i very small. 



