160 THE ENtOBiOiX)GIST*S RECORt). 



destined to be white upon the mature wing are now completely 

 formed, and undergo no further changes, hence, ontogenetically speak- 

 ing, the white spots (? scales. J. W. T.) upon the wing are the oldest of 

 all." Here we would ofier two notes of criticism : (1) That the white 

 scales of an insect's wing are of tAvo entirely different classes. Some 

 white scales are quite richly pigmented (see Kntoui. lur., vol. vi., 

 p. 35 et se(]., 109 et scq., 204 it seq.). The white areas of the wings of 

 An/c (/ncdat/ica, the white spots on the wings of !^i/rirJit/nif: iiialcae, and 

 numerous other examples, have been already fully discussed. '••' (2) That 

 the whole of the scales (pigmented and unpigmented) are supplied 

 with air, only in the final stage of their development. 



The secretion from the hfemolymph (= the " pigment factor " of 

 Riding), which fills the scales destined to become pigmented, now 

 enters them. It does not enter scales which will finally be white 

 (due to air contents), but does, in many insects, enter other scales, which 

 are ultimately white. Mayer says the htemolymph of the chrysalis, 

 which is a clear amber yellow fluid, now enters them, but Chapman 

 has already adversely {aiiti', pp. 78-79/ criticised this view, and has sug- 

 gested that only a secretion of the lupmolymph does so. The material 

 in the scales now becomes " ochre-yellow " in tint, whatever their 

 ultimate colour is destined to be, and, having remained in this stage 

 for about 24 hours (in the case of A. archqipm), the mature colours 

 begin to show themselves. " These mature colours always appear 

 first within scales which are situated between the nervures. They 

 are faint at the beginning, but gradually increase in intensity. For 

 example, if a scale be destined to become black, it first becomes pale 

 greyish-brown, and this colour gradually deepens into black. f This 

 pigment is no doubt derived from the haunolymph within the scale 

 at the time when it first appears. It is probably produced by che- 

 mical processes that are somewhat analogous to the clotting of the 

 blood, for the pigment is found to be sublimed over all the surfaces of 

 the cavity of the scale, the layer of pigment being especially thick 

 upon the upper surface of the scale." 



III. — The probable chemical and physical nature of the pig- 

 ments OF Lepidoptera. — Landois, in 18G4, found that when the 

 blood of beetles and butterflies was allowed to evaporate in the air, 

 crystals separated out. He also found that the blood consisted chiefly 

 of egg-albumen, but that globulin, fibrin and iron were present. He 

 further observed, that when the blood was allowed to dry in the air, it 

 generally became brownish or yellowish, and that while the colours of 

 the blood were different for different species, the colour assumed by the 

 dried blood was apt to be similar to the ground-colour of the wings of 

 the mature insect from which the blood Avas draAvn. 



Mayer states that he believes the pigments of the scales are derived 

 from the ha^molymph, or blood, of the chrysalis ; and his chief reason 

 for believing this is, that he can find no evidence that there is any- 

 thing but h!i3molymph Avithin the scales during the time that the pig- 

 ment is formed. Chapman doubts AA'hether the crude h^emolymph ever 

 enters them, but thinks that a secretion from it does so, and that the 



* " The genetic sequence of insect colours." — British Noctuae caul their Varieties, 

 vol. ii., pp. i.— xviii. 



+ This fully bears out our contention as to "pigmentary blacks." — Brit. 

 NocL, ii., pp. vi. — vii. ; Ent. Record, vi., pp. 38-40 and pp. 104-111. 



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