26 BRITISH BUTTERFLIES. 



tion, p. 135) that, in some exotic species, it is nearly half-an-inch long, 

 is of a blood-red colour, etc., and he concludes, from its appearance, 

 mode of use, and the complicated arrangement of muscles that have been 

 developed for its protrusion and retraction, that it serves as a protec- 

 tion to the larva by startling and frightening away some enemy when 

 about to seize it, and, further, that its possession is one of the causes 

 which has led to the wide extension and maintained the permanence 

 of this now dominant group. Its apparent restriction to this particular 

 group of butterfly larvse suggests strongly that the highly-modified 

 Thaine and Parnassiine branches are merely outward expressions of 

 this dominance, the latter having, as it were, forced its way into high 

 mountain -regions where ib alone, of this huge group, occupies the field, 

 whilst the former, highly specialised in its food-habit and early time of 

 appearance, is most successful in limited areas already supplied with 

 an exceedingly numerous, competitive, butterfly fauna. At any rate 

 the possession of the osmaterium is possibly one factor that has spelt 

 •' success " for this group in the keen struggle for existence that is 

 taking place in all parts of the world, where the species of this group 

 have more than held their own against all other insect competitors. 

 Davidson and Aitken, writing of the use of the osmaterium in the 

 larvae of the Papilios and Ornithopteras, state (Journ. Bomb. Nat. I-Jixt. 

 Soc, v., p. 361) that there can be no doubt that its purpose is for a 

 defence against hymenopterous and other parasites that seek to attack 

 them. They state that the osmaterium of the larva of Papilla hector emits 

 a reddish, possibly corrosive, fluid with an offensive smell, and they 

 further observe that they have noticed larvae, when disturbed by ants, 

 drive them off by swinging the head round with the tentacle extruded. 

 Edw T ards is quoted by Scudder (Butts. New Engl., ii., p. 1273) as saying 

 that the larva3 of IpJiiclides ajax rest throughout life exposed on the 

 surfaces of the leaves, but that they appear to be effectually protected by 

 the extrusion of the osmaterium, which gives out a peculiarly acrid or 

 sickening odour. Fioersheim states (Ent. Bee., xxi., p. 115) that the 

 larvse of L aja.e are less inclined to use their osmateria than those of 

 Laertias philenor and Papilio machaon, whilst he considers that 

 Edwards' account of the stench produced by the acrid secretion is 

 very greatly exaggerated, and that, to him, though somewhat stronger 

 than that of P. machaon, it is no whit more disagreeable. Buckler 

 says (Larvae, etc., i., p. 3) that, when the larva of Papilio machaon 

 extrudes its osmaterium, the protrusion is accompanied by a drop or 

 two of clear greenish liquid, and a most penetrating odour, reminding 

 one of an over-kept, decaying, pine-apple. Durban notes (( 'an. 

 Nat., v., p. 87) that the larvse of Jasoniades glaucus, if disturbed, 

 rock themselves slowly from side to side, throwing out the forked 

 orange lenticle, which emits at the same time a very acrid odour; 

 Scudder, however, says that, when halfgrown, the odour from the 

 larvse seemed very faint and not unlike that of a spice-bush [Benzoin) 

 but somewhat acrid. ]\v. adds that Neal says that the osmaterium of 

 tieraclides crexphontes emits a, very disagreeable odour, and avers that 

 no birds attack the larvae of this species, and that the shrike, which is 

 almost omnivorous, will not touch it. nor will the bee-martin, nor the 

 mocking-bird. Scudder further observes (Butts. New /\>ial..\). 1828) that 

 Abbot says that, in the southern States, owing to its musky odour, the 

 Larva of Euphoeadm troilus has gained the name of " mellow bug." but 



