1880. j 53 



The period of incubation varies, within my observation, from 

 fourteen days to six, according to the season and the temperature. 

 The first eggs I obtained this year were laid on the 6th of April, and 

 hatched out on the 20th. In 1877 I had eggs in the third week in 

 August (the warmest in that year), which hatched in six days. From 

 that date the period of incubation gradually increased again to eight 

 and eight and a half days. When hatching is imminent, a sudden and 

 obvious change comes over the batch of eggs ; the clear yellow colour 

 has given place to a darker muddy discolouration, due apparently to 

 the development of black warts and spiracles and oblique lines of hairs 

 on the body of the larva, and to the complete detachment of the larva 

 itself from the enclosing shell. Conspicuous at this stage, on the 

 dorsal surface, are four relatively large, somewhat triangularly-shaped, 

 blackish spots (warts) seated on the meso- and meta-thorax in a 

 quadrate form, and which I call the thoracic square. Within and 

 behind these are, on either side the median line, two rows of black 

 hairs, appressed, and running obliquely backwards and inwards. In 

 front of the thoracic square the head of the larva is noticeable by its 

 translucency, while the slightest inclination to one side or other brings 

 into view the eye-spots, a group of five reddish points on each side of 

 the head. Seen laterally, and perhaps seen more distinctly at a some- 

 what earlier stage, because not then liable to be confounded with the 

 antennae and palpi, these five eye-spots are grouped, four in a diamond 

 whose long axis points obliquely backwards and a little ventrally, whilst 

 the fifth, somewhat further away on the ventral side, seems to lie in 

 the continuation of a concave anteriorly, crescentic line, formed by 

 itself and the two anterior eye-spots of the rhomboid. Assuming the 

 head to be composed originally of annular segments, these three eye- 

 spots would seem to lie on one, the remaining two on that immediately 

 posterior to it. 



The larva now exhibits slow but constantly repeated vermicular 

 movements ; the mandibles open and shut ; the tail is generally re- 

 curved towards the dorsum. There is, as it were, a crowding forward, 

 and an endeavour to advance in the shell by vermicular movements 

 chiefly, and in which the legs take no part, while the anal pro-leg is in 

 frequent requisition. The large warts of the thoracic square, armed 

 with double hairs, are constantly sliding backward and forward along 

 the shell. At last, an invisible slit in the longitudinal line of two of 

 these warts on one side is effected, revealed at first only by the slow 

 erection of a hair which has escaped through it. There is a hump or 

 protuberance near the head, seeming to be formed by the prothorax, 



