322 RIIOPALOCEKA MALAYANA. 



a stout medial spur. Laiva; stout, subcylindrical ; tlie prothoracic 

 segment furnished with two retractile tentacles.* 



Anterior wings having the lower discoidal nervule united to the 

 median nervure, and thus appearing as a fourth median nervule. 



The I'apilionimv, by the above detailed characters, are the 

 most distinct and easily recognised subfamily of Rhopalocera. 

 Fig. 10+. - .interior wing oi PapiUo rp^ apparently four-branclied median nervure of the anterior 



memnvn, showing position of median i. I J 



nervuies. wiugs is found in no other group of butterflies, and is a 



neural feature of so simple and clear a character that a glance at the wings is sufiicient to 

 decide whether a butterfly belongs to the PupiUoiiinie or not. The larvte, again, possess an 

 extraordinary organ in a Y-shaped tentacle situate on the prothoracic segment, which, 

 concealed in a state of repose, is capable of being suddenly thrown out l)y the caterpillar when 

 alarmed. On this point Mr. Wallace has well remarked: — "When we consider this singular 

 apparatus, which in some species is nearly half an inch long, the arrangement of muscles for 

 its protrusion and retraction, its perfect concealment during repose, its blood-red colour, and 

 the suddenness with which it can be thrown out, we must, I think, be led to the conclusion 

 that it serves as a protection to the larva, by startling and frightening away some enemy when 

 about to seize it, and is thus one of the causes which has led to the wide extension and 

 maintained the permanence of this now dominant group." f 



This subfamily includes but few genera, its strength lying in the genus Papilio itself. 

 Three genera — or, as treated here, two genera and one subgenus — are found in the Malay 

 Peninsula, and, excluding Tetnopalpus, + there is little probability of more being found, 

 as the others are principally denizens of higher altitudes. These three genera, however, 

 viz., Ornitho])tera, Papilio, and Leptocircus, are of very unequal value, the first two being 

 almost inseparable, in a structural sense, if we retain the genus Papilio in its old and 

 undivided condition. There can be no question that in Papilio, as thus understood, we 

 do find structural and neural characters that in other subfamilies are ranked as correctly 

 proving the existence of distinct genera, and which, if the useful though artificial canons 

 of classification were here rigidly adhered to, would compel the generic disintegration 

 of I'apilio4 The objections, however, to that course appear to have at least considerable 



•■= Prof. Westwood (lutrod. Mod. Class. Ins. vol. ii. p. 348) states that the larvae are " never viUose nor hairy," but this 

 does not appear to be always true in the earlier stages of development, as Mr. Forsayeth describes the young larvae of Papilio 

 erittioaius as differing greatly "from the mature caterpillar, having numerous processes, armed with stiff hairs or spines, 

 along either side and head" (Trans. Knt. Soc. 1884, p. 386). 



\ Trans. Linn. Soc. vol. xxv. p. '6 (1805). 



The use of this organ has been observed in the common Palitarctic Ijutterfly, Papilio machaon. Bonnet states that 

 when he pressed this caterpillar, near its anterior part, it darted forth its horn as if it meant to prick him with it, directing it 

 towards his fingers ; but withdrewiug it as soon as he left off pressing it. " This horn smells strongly of fennel, and probably is 

 employed by the insect, by means of its powerful scent, to drive away the flies and ichneumons that annoy it " (Kirby & Speuce, 

 Introd. Ent. 7th ed. p. 418). Rennie observed the same action in larvie of the butterfly found feeding on fennel m the Jardin des 

 Plantes at Paris, and concludes that it might be " intended to intimidate the ichneumons from depositing then- parasite eggs 

 in its body, or warning ofl' the thrushes or the carnivorous locust {Acrida vcrrucioora) from devouring it. On the same plant 

 indeed where these caterpillars were feeding we saw one of the latter lurking about, no doubt with evil intent " (' Insect 

 Miscellanies,' pp. 53-4). Mr. Forsayeth describes the larvae of Pajnlio erithonius as foinid at Mhow, in Central India, and 

 speaking of these tentacuhe, states that "on pressure between finger and thumb, a double horn, soft and erectile, of a pink 



colour, shoots out and quivers slightly When extrusion takes place a rather pungent, aromatic, but certainly not 



disagreeable, odour is given out. The larvie seldom shoot forth these processes on being handled or irritated, but only on 

 pressiu'e being made" (Trans. Ent. Soc. 1884, p. 380). The odoiu' thus emitted is not, however, always pleasant, as Lacordaire 

 has informed us: — "Dans certaines especes Ainericaines {Pajiilio Craisus, Archelaus, &c.), que nous avons eu occasion 

 d'observer, cette odeur est plus ou inoins desagreable" (Introd. a Tentomol. i. p. 108). 



I A genus found in North-Eastorn India. 



§ The Ceylon species have thus been treated by Mr. Moore (Lep. Ceylon, vol. i.). 



