AGEIADES THETIS. 367 



wide, the special structure of the top less obvious than in the previous 

 instar ; the upper surface has, however, a distinctly crenated margin. 

 The len tides still appear to have perfectly smooth outlines. There are, 

 on each side, nine hairs and lenticles on each segment to each dorsal ridge 

 and twelve between this and each spiracle. The hair of tubercle i is still 

 distinguishable. The incisions are well-marked and each segment 

 rises into a hump on each dorsal ridge. The hair-bases first show the 

 stellate points round their equators, most marked on the posterior 

 hairs, but varying a good deal in different specimens ; they are, when 

 fairly developed, six or seven very sharp points, half-way up the hair- 

 base, and of a length equal to about one-tenth of its thickness ; the 

 hair-spicules are still numerous, very fine and sharp, but less crowded 

 than in first instar : the abdominal segments show, on each side, three 

 large (O30mm.) and one short hair amongst which to locate the setae 

 of i and ii ; dorsal to these are one long and one short hair, one or 

 other of which is often absent ; between i and ii and the spiracle are 

 four or five short hairs and as many lenticles. The subspiracular or 

 flange-hairs are nine in number, two or three longer, the others vary 

 down to a very short one ; the marginal series presents some five hairs 

 and two or three lenticles. The honey-gland and fan-organ are well- 

 developed. Each pad of the prolegs has two or three equal hooks the 

 middle one the largest. Fourth instar (two larvae. March 18th, 1907): 

 The smaller 3-5mm. long, the other 5-0mm., width l'7mm. The 

 smaller, from the crowding of the dark hairs, looks much deeper in 

 colour than the other ; apart from hairs both are of a dark olive-green, 

 with bright yellow flange nearly continuous and dorsal flanges yellow, 

 but in patches, one on the summit of each lateral hump on the 2nd 

 thoracic and 6th abdominal segments, i the width of the larva apart on 

 the mesothoracic. J or less on the 6th abdominal. The prothoracic 

 plate is in a deep hollow under the overhanging mesothorax. The black 

 spiracles are conspicuous, as well as the glandular patch on the dorsum 

 of the 7th, and the pair of caruncles on the 8th, abdominal segments. 

 The black hairs are also a prominent feature. The larva in this instar 

 shows very definite series of long hairs on the dorsal (setae of tubercles 

 i and ii) and lateral (setae of tubercles iv and v) flanges, moderately 

 long hairs on marginal prominence (? setae of tubercle vi) with many 

 short ones elsewhere, e.g., on the 3rd abdominal segment on the dorsal 

 flange on each side are 3 or 4 hairs about 035mm. long, and about a. 

 dozen from that down to Olmm. long ; about 50 (from 0-04mm. to 

 0-08mm. long) between these and the marginal hairs ; the latter have 

 7 or 8 of a length of 0-25mm. to 0-3mm ., and about a dozen smaller, there 

 is a vacancy between these and the marginal group of 2 or 3 of 0*3mm. 

 and 16 or 18 smaller, and again about 20 to 24 at bases of prolegs, 

 the longest about 0-15mm. There are a few rather longer (0-4mm.) 

 hairs on prothorax, those on last segments are not longer but rather 

 thicker. Lenticles are abundant on the " slopes " especially about the 

 spiracles and again about the honey-gland where are a good many 

 special clubbed and curved hairs. The lenticles are usually round but 

 sometimes angular. The hair-bases of the smaller and special hairs 

 are very spiked, but flat and shallow, those of the longer hairs are pro- 

 portionally much taller, but the spikes are still small thorns, half-way 

 up inconspicuous and often nearly obsolete. The special hair of the 

 angle of the prothoracic plate is very slender, about 0*25mm. long, the 



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