CARNIVOROUS BUTTERFLIES CLARK 469 



They are minute holes with no marginal structure. Some trace 

 of the true sj^iracles can be seen at a little depth within them, accom- 

 panied by a scalelike outer margin. 



Perhaps the most remarkable thing about this larva is the modi- 

 fication which has affected the prolegs. AVhen we examine the soft 

 under side of the larva the head, true legs, and prolegs are seen 

 very much as in the 3'oung larva. The head, however, is nearly 

 white, and so are the true leg^ except for the tarsal tips. 



Beginning at the margin of the dorsal shield one finds that the 

 shagreened points of the general surface carry hairs of various 

 lengths, some almost evanescent, others nearly 0.25 mm. long. 

 These no doubt assist in making the apposition of the larva to its 

 resting place more complete. They seem to be true hairs jointed at 

 the base, and the points on the dorsum are probably also really hairs 

 rather than spicules. 



The shagreened dots are about 0.08 mm. in diameter. As one 

 passes inward from the margin the hairs get rather thicker, and 

 retain their length of from 0.20 to 0.28 mm., the shagreened bases 

 lose all chitinous color, and a short way in there is apparently a 

 smooth surface thickly studded with white, short, thick hairs. As 

 we approach the prolegs these get shorter and sharper, ttnu fail 

 altogether at a line just below the summit of the column at the top 

 of which is the retractile portion of the leg. There, just at the mar- 

 gin of the summit of the column, is a compact circle of crotchets 

 that differ in no very decided manner from those ordinarily found 

 on prolegs. Within this circle is a white projecting mass of tissue 

 with a ridge along its summit from front to back, with parallel 

 striae running down to the margin. The crotchets are hooked out- 

 wards, have a short flat base applied to the surface of attachment, 

 and, without forming two or three regular rows, are in more than 

 one row. The little smooth space outside them gives them room for 

 movement without being interfered with by the hairs that clothe 

 the rest of this under surface. 



These circles of crotchets, which are to all appearance identical 

 with the complete circles found on the prolegs of " micro " larvjB, 

 are not the ordinary crotchets at all, but an entirely new structure. 

 The true crotchets exist in the young larvae, but in this full-grown 

 one are merely represented by the striae on the central fleshy mass 

 noticed, which is really the true proleg. The crotchets here existing 

 are around the summit of the pillar, at the center of which the true 

 proleg is often placed. Doctor Chapman says that its method 

 of working must be very similar to that of the " micro " full cir- 

 cle, but instead of having a central tendon as they have it has the 



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