NOTES TOWARDS A LIFE-HISTORY OF THESTOR BALLUS. 277 



Notes towards a life=history of Thestor ballus {with thnr plates). 



By T. A. CHAPMAN, M.D. 

 ( Concluded from p. 260.) 

 May 31st. — Two specimens moulted, apparently into last skin, after 

 resting nearly three days. The point that strikes one at once is the 

 existence of two white processes just behind the 8th abdominal spiracle, 

 apparently eversible glands. These disappear, leaving only a pale 

 mark (from which they can be everted) after a few hours, and, on 

 examining a larva in previous skin these same marks can be seen on 

 it, but only as inconspicuous slightly paler spots. The chief difference 

 between the tAvo larvae (in this and previous skin) is in the differentia- 

 tion of the hairs. In the previous (penultimate) skin the hairs are 

 much more uniform in size over the whole surface ; in reality, they are 

 triflingly longer and shorter, but not very noticeably. In this skin, the 

 hairs may be described as occurring on the dorsal yellow bosses and on 

 the subspiracular flange, and again at a lower level. The " slope " 

 has only very short hairs, that look as if of a different series to the 

 others. The depression of the 1st thoracic plate is still marked. The 

 larva will probably be easier to describe when fuUfed ; meantime the 

 row of dorsal (yellow) bosses stands out well as humps, and the lateral 

 flange is very pronounced. This will probably be less so as the skin 

 becomes more distended. The larva can put its head out, with mouth- 

 parts straight forward, straightening out the " marginal flange " of 

 prothorax, and making it vertical and not horizontal, making obvious 

 to sight that the said flange goes over the dorsum of the segment, and 

 has no real relation, morphologically, with the marginal flange, in spite 

 of being, both apparently and functionally, continuous with it. In this 

 stretched attitude these " marginal " front parts of prothorax rise to 

 much the level of the rest of the larva, but the prothoracic plate 

 remains at the bottom of a deep sulcus behind them, and reminds one 

 most forcibly of the "neck" of the skippers. It is extremely pro- 

 bable that it is really related to the neck of the skippers ; this and the 

 " lenticles " are strong points to be added to others connecting the 

 Hesperiids and Lycsnids more closely together than either to the other 

 butterfly families. 



In the earliest part of its existence in its last skin the larva has still 

 much of the colouring of the earlier stages. It is only 8mm. or 9mm. 

 long (when at rest). The dorsal prominences are bright yellow, and 

 the slopes below, if not quite so bright, are still yellow, and their 

 other markings and colours are not much modified from those of the 

 previous skin. The prominences are still very marked. The last two 

 thoracic and first six abdominal (eight segments) have a large 

 prominence (yellow) on either side of the dorsum, and carrying seven 

 black and five white hairs, about 0"8mm. long, with a few others very 

 short, that rather, perhaps, belong to the hairs of the general surface, 

 but are actually intermediate in position, and are a trifle longer and 

 straighter than the general surface hairs. Then follows the sub- 

 spiracular flange, also yellow, well below the spiracle, and also 

 carrying about five long white hairs, not quite 1mm. long, and more 

 numerous but shorter black ones, that shade more gradually into the 

 general surface hairs than do the dorsal ones. This flange appears to 

 go round the prothorax and 9th abdominal segment ; really, of course, 

 November 15th, 1904. 



