ON THE LARVA OF ARCTIA CAIA. 267 



The newly-hatclied larva is deep fuscous in the first stage, but soon 

 becomes black or nearly so, the hairs and tubercles being black and 

 obscuring the fusco-rufous skin, till, after feeding, the tubercles separate 

 from each other enough to expose it, and it becomes a larger element in 

 the larval colouring as it grows. This change with gTOwth is even 

 more marked in the three following skins. The larva, at first densely 

 hairy, and taking its general aspect from the colour of the hairs, 

 gradually, with its growth, exposes the intermediate skin and the hairs 

 become a less marked feature, till, when full-grown in each stage, the 

 colouring of the skin, rather than of the tubercles and hairs, gives 

 character to the larva. The length of the larva in the first stage is 

 2*3 mm., growing to 4 or 5 mm. The head is black, the second segment 

 has a black plate carrying eight hairs beneath its front angle, and in 

 front of the spiracle is a tubercle carrying two hairs, and another lower 

 down carrying one. On segments 3 and 4 are, on either side, a dorsal 

 tubercle carrying two hairs and a sub-dorsal carrying one, these taken 

 together seem to range with the dorsal plate of second segment. Below 

 is a largish tubercle with one hair in line with the i)re-spiracular on 2, 

 and a lower one in same line witli the lower on 2. On each of these 

 three segments is a small tubercle without a hair, immediately above 

 and behind the pre-spiracular tubercle. 



On the following segments 5-12, are a small anterior and a larger 

 posterior trapezoidal tubercle, each with one hair, a large supra- 

 spiracular with two hairs, and a post-sjiiracular with one. All these 

 are angulated, with sides flattened against each other as if flattened by 

 mutual pressure, precisely as I have noted in the Acronydas. There is 

 also a sub-spiracular tubercle Avith one hair, and two lower ones less 

 marked and Avithout hairs. The base of the prologs carries a large 

 tubercle-like plate. The true legs have three chitinous joints, as well 

 as some basal jilates, with a curved claw and battledore palpus at the 

 end of the third joint. 



The prolegs are of circular shape, expanded at end of a pedicle, 

 with four hooks in inner 3/5 of the edge ; five hooks occur on 9 and 

 10, at least in some instances. 



In one specimen the post-spiracular tubercle on 12 carried two 

 hairs. The thirteenth segment has on either side a large square 

 tubercle with four hairs, and a lower smaller one with one hair. The 

 fourteenth segment carries an anal plate, with six hairs much shorter 

 and smaller than the others, the general hairs being from once to twice 

 the diameter of the larva in length, these on the anal plate about one- 

 third of the diameter. The anal prolegs seem to be of the same 

 structure as the ventral. The hairs are very finely spiculated. 



In the second skin the length reaches 5 or 6 mm. The structure 

 and appearance are much as in the previous skin. The tubercles have 

 more hairs, except the anterior trapezoidal, which retains one. The 

 posterior trapezoidals have eight or nine ; the supra-spiracular five or 

 six ; the sub-spiracular, four ; the marginal and ventral, each four ; a 

 plate on second segment ; two large and one smaller tubercles on each 

 side of 13. The legs preserve the battledore palpus, and the prolegs 

 are now more expanded and flange-shaped, i.e., they have a flat fan- 

 shaped surface directed towards the middle line ; this carries four hooks 

 on 7 and 8, five hooks on 9 and 10, placed on the middle portion of the 

 fan, with a margin at each end, as if for more hooks that do not yet 

 exist. Segment 12 has nearly lost the ventral tubercles. Three large 



