38 BRITISH LEPIDOPTERA. 



projected, would take part in locomotion. The modification of the 

 prolegs and the method of progression, is, without doubt, designed to 

 enable the larva to move freely over the smooth upper surface of 

 leaves, which it could not well do under ordinary conditions. The 

 sticky condition of the abdominal surface supports this view, but there 

 can be no doubt that they spin some small quantity of silk on which 

 they walk, as do so many other lepidopterous larvae. 



Besides the tubercles, which have fairly fixed positions on the seg- 

 ments, the skin has, scattered more or less regularly over the body, 

 little elevations, resembling, somewhat, a fine pile or covering of minute 

 hairs. This pile is a very common feature in butterfly larvae, is sup- 

 ported by very minute papillae, and is generally distributed with con- 

 siderable regularity, usually in a transverse, though sometimes in a 

 longitudinal, direction. It is, however, occasionally scattered irregularly 

 all over the body. When it is arranged transversely, it is usually some- 

 what closely related to the subsegmental divisions into which the seg- 

 ments are divided. Bacot says that this pile, which appears something 

 like a clothing of short pointed spines, is very common in lepidopterous 

 larvae in their first skin, and, in some, is so fine that a one-fourth lens 

 (or even higher power) is required to detect it. The minute spines or 

 hairs are often only visible at a certain angle, or when the edge of the 

 dorsum is silhouetted against a bright background. In some larvae 

 this coat is lost at the first, or at a subsequent, moult ; in others, it 

 persists throughout the whole larval existence, becoming just a trifle 

 coarser at each moult. The larvae of D icy da oo, Dianthoccia curpo- 

 phat/a, and Taeniocampa pulverulenta fcruda), among many others, 

 illustrate this phase of its development. Bacot is of opinion that 

 primitive and secondary hairs are of different origin, the former arising 

 from the primitive setae or tubercles, the latter from the minute hairs 

 forming the pile just described. He is also of opinion that the bifid 

 shagreen hairs of Smerinthus, the dense clothing of short secondary 

 hairs in some Lasiocampids, the short pyramidal granulations of cer- 

 tain Liparids, and the highly specialised secondary hairs of some 

 butterfly larvae, are evolved from the minute hairs, which in their 

 simplest condition, form the pile above described. 



That this pile is found rather generally among larvae is proved by 

 the following, very incomplete, list furnished by Bacot. ZYG^SNIDES : 

 Adscita statices and Anthrocera trifolii (both in first skin). LASIOCAM- 

 PIDES : Trichiura crataegi. BOMBYCIDES : Boinbyx mori (very fine). 

 GEOMETKIDES: Phorodesma smaragdaria (first stage, skin granular later). 

 PLATYPTERYGIDES : Drepana cultraria. NOTODONTIDES : Leiocanipa 

 (Pheosia) tremula(dictaea), black in first skin, no trace in second, except 

 on horn, Diloba caeruleocephala (in first stage), Odontosia caniiclita 

 (faint traces in third skin), Phalera bucephala (in first and second 

 skins, (?) developed into secondary hairs later on). LIPARIDES : Dasy- 

 cltira fascelina(in first skin), Demas coryli (strong in first, small in 

 second to fourth skins), Orgyia antiqua (distinct but fine), Leucoma 

 salicis&Q(iPsiliiramonacha(in first and second skins), Portliesia similis. 

 ARCTIIDES: Spilosoma lubricipeda (first to third skins, small), S.fuligi- 

 nosa (first and (?) third skins), Arctia villica (first to fourth skins), 

 Callimorpha dominula (strongly developed), Euthemonia nissula (first to 

 fifth skins), Kuclielia jacobaeae (first skin). N GLIDES : Nola cuculla- 

 tella (in later stages rather granules than prickles). NOCTUIDES ; 



