252 



Transactions . 



. C. — Mesothorax of male 

 larva in 5th instar (note 

 coalescence of i and ii, 

 and increased size of other 

 tubercles). 



minute irregular white areas are scattered over the body, especially on the 

 ventral and lateral surfaces. During the last four stadiums the pile on 

 the body has been getting not larger or more distinct, but much denser, 



and covering the whole surface of the body. 

 6th stadium : Duration, 23rd April to 4th 

 May, twelve days. Length immediately after 

 fifth moult, 1 in. ; full-grown, 1| in. The black 

 line along the central facial suture and the 

 black margin to the clypeus are now missing. 

 Black cheek-stripe very conspicuous, some- 

 times consisting of two separate short stripes 

 end to end. Head small, non-retractile, light 

 green in colour. The labrum is large, white, 

 and conspicuous. Mandibles serrated. True 

 legs and prolegs light green. Medio-dorsal 

 and subdorsal stripes as in last stadium. 

 Supraspiracular line ditto. Spiracular line 

 white, broad, very distinct. Numerous small 

 white areas on ventral and lateral surfaces, 

 as in last stadium. Prolegs furnished with 

 semicircle of crochets. Spiracles placed later- 

 ally, situated a little beneath and in front of the central portion of 

 the abdominal segments, near the hind margin in the prothorax, oval, 

 brown with dark margin, inconspicuous, those in the 1st thoracic and 8th 

 abdominal segments greatly enlarged. Tubercles all bearing single simple 

 dark-coloured hairs. Pile very dense, extremely minute, seemingly com- 

 posed of short thick black-tipped bristles. 8th abdominal segment bearing 

 large posterior dorsal hump, the body being much attenuated from it towards 

 the head. Body cylindrical, slightly flattened ventrally. Tubercle iii is 

 well developed, and is surrounded by a large pigmented area, greatest in 

 the 1st abdominal segment, and diminishing in the 2nd, 3rd, and other 

 abdominals. Arrangement of subsegments same as in 1st stadium ; tubercles 

 as in stadium 3. The hairs, which can be no decided protection to the 

 body, are set in a peculiar manner, each one having a direction opposite 

 to that of those immediately above and below it : for instance, i is directed 

 up and forward ; ii posteriorly and up ; iii outwards, forward, and up ; 

 iv outwards, downwards, and back ; v downwards, forward, and out ; 

 vi downwards, backwards, and out. This must surely be the beginning 

 of a more elaborate protective system. Concerning the coloration of the 

 tubercles, i is white, iv and v are white in the 3rd thoracic segment and 

 abdominals ; in the first nine abdominal segments all the tubercles are 

 white except iii ; there are no black tubercles on the last abdominal. 

 Prior to spinning, the body becomes much lighter in colour, and the dark- 

 green supraspiracular stripe becomes most conspicuous. The spinning of 

 the cocoon takes place some six or more days prior to the final moult. A 

 considerable amount of variation occurs in this stadium, details of which 

 are given in the following paragraph. 7th stadium (extra moulter) : All 

 tubercles white, excepting those on the caput. The black cheek-stripe is 

 very inconspicuous, and sometimes entirely absent. 



Variation. 



Larva. — -In the 5th and 6th stadiums there is a certain amount of 

 individual variation in the colouring of the tubercles. The most important 



