234 Transactions. — Zoology. 



tubercles, setae, and spiracles brown ; faint pale spiracular 

 line, tbe skin above being really darker tban below. Anterior 

 segments darker tban posterior. 



Structure : Prothorax (fig. 6) apparently as in first stage. 

 Meso- and post-tborax bave an additional tubercle. Careful 

 comparison of first and second stages induces me to think 

 this is not the one immediately above the leg, but the pos- 

 terior tubercle above it in position. Abdominal segments 

 also have an additional tubercle above the legs in a pos- 

 terior position. The posterior subspiracular tubercle ap- 

 pears to be rather lower down in relation to the spiracle than 

 in the first stage. The abdominal feet bear three pointed 

 setae ; the first two pairs are larger than in first stage. 



In succeeding changes of skin the abdominal feet gradu- 

 ally become normal. This, I think, takes place not earlier 

 than the fourth skin, but I have no note on this point. Adult 

 markings are also gradually assumed. In that skin preceding 

 tiie last, two larvae confined in the same pot of grass assumed 

 entirely different plumage as regards colour, one being wholly 

 green, the other brown (this was probably green, more or 

 less, ventrally, but I omitted to note). This striking differ- 

 ence is not unusual amongst Noctua larvae, and appears to 

 be attributable to environrnental causes. One at least fre- 

 quently rested during tbe day-time on the reddish earthen- 

 ware pot. In a state of nature they rest on the earth, or 

 on a stem of food near the earth. The exciting cause of tbe 

 variation may be considered to depend on whether the larva 

 rests habitually on the earth or on the stem. In the former 

 case we might expect them to assume a brown colouration, in 

 the latter green, each being to respective individuals equally 

 protective during the period of rest from feeding. 



Immediately preceding pupation the length is about 1 in. ; 

 colour above spiracular line reddish-brown, below pale-green 

 (the larva mentioned above lost its green colour at last ecdy- 

 sis). A rather indistinct medio-dorsal line is marked more 

 distinctly at the incisions as a brown spot. Thm dark sub- 

 dorsal line is edged with lighter, and very distinct dark 

 spiracular spots on all the segments. In preceding stage 

 these were oblique dashes. The clypeus of head is dark- 

 brown, middle of lobes a dark streak, edges dark- brown. 

 Under the microscope the larva-skin is mottled, and the 

 pattern of markings not apparent. No doubt the larva is 

 more inconspicuous to small foes than to our eyes, which 

 take the whole form and markings at one comprehensive 

 glance. Even so. to us the larva seems wonderfully protected 

 by its colouration when at rest. 



1 omitted to note the exact duration of larval existence. 



