( IXV ) 



has the spines mostly along the outer edge, where they become sometimes very 

 stout aud long {Proserjiiiuis : Arctonotiis). The spurs of the tibiae are organs 

 of much importance in the classiiication of Moths, their number and length 

 being constantly made use of in systematic works iu the definition of genera. 



The epiphysis or s]inr of the foretibia,* which we consider homologous with 

 a proximal spar of the hindtibia, varies in length and position in tlie Sfthingidae. 

 It is never absent, as in C/ialcoxiiilac for instance. The most remarkable form 

 is that iu which the fringe is obliterated {Ceridia). The midtibia has one pair 

 of slender spurs, which end iu a naked point as a rule and are pro.ximally 

 generally cylindrical. They are sometimes of the same length, bnt as a rule the 

 outer or anterior one is shorter. A quite excejitional development fonnd among 

 the species of the American Choerocampine genus Xylophanes leads to the outer 

 spur being the longer one of the two. The variation in length is considerable, 

 the longer spur being sometimes as long as the tibia and frequently barely 

 longer than the tibia is broad. There are on the spurs generally some long 

 hairs, which develop often into spines. The spinosity of the spurs is a feature 

 often met with in species with spinuse tibiae, aud is, like the latter, a sign of 

 reduction or weakness. 



In some cases we find a series of stiff scales along the side towards 

 the tarsus, resembling a serrated crest {Afae/-oi/los.iit/H) ; while there occurs a 

 conspicuous coaib of bristles on the shorter spur in Nfi/hele and Ci;ntrocten% 

 (PI. LXIV. f 8). The comb of Nepkele and Centroctenn has most likely the same 

 function as the comb of the tarsus, as described below. The midtibial spurs are 

 never absent from Sphingidae. 



The hindtibia possesses normally two pairs of spurs, one terminal, and 

 the other more proximal, situated sometimes in or near the middle of the tibia, 

 sometimes near the terminal spurs. The shape and structure of the hiudtibial 

 spurs resemble tliose of the midtibia : they are longer on an average, the longer 

 apical hiudtibial one being never shorter than the longer midtibial one, but 

 very of'teu surpassing it in length. They are less often sjiinose ; the inner one is 

 never shorter than the outer one of the same pair, and tiie comb or crest found 

 in Nephele, etc., is less strongly developed. Tlie proximal pair disappears very 

 often. The gradation from a tibia with long proximal spurs to one without a 

 trace of them is comidete, there being many species with very short spurs, and 

 one {Parum porphyria) iu which there are two very short proximal spurs or 

 only one or no spur. Here we have a case where there can be no doubt about 

 the direction of the line of development. The absence or reduction of the 

 proximal pair of spurs is a specialisation, the species thus characterised repre- 

 senting a younger stage of development than those in which the proximal spurs 

 are long. And therefore we can safely conclude that also iu the case of the 

 midtibial spurs siiortness is a sign of reduction. Short spurs are seldom found 

 outside tiic Arhfrontiiiiai', and AmliidiciniK-, and the cases wlieri! tiie proximal 

 pair of the hindtibia is alisent are nearly all coiHined to those two subfamilies, 

 • KiiUiiciiicji-, niu^lr. Zcit.vin: Kiilniii. iv. \<. llii. IHI. I'Lite (l«!ll)). 



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