2-iC Dr^ T. A. Chapman's 



Centaurea at the places we visited in Spain brought to 

 a very early conclusion my attempts to rear the two 

 species side by side. 



The account given in 1900 of the egg of 0. tristis and 

 of the hatching of the larva is correct as far as it goes, 

 but wants much supplementing. When the larva is ready 

 to emerge it shows very visibly through the egg-shell 

 three black patches on either side, just above the spiracular 

 line, on the 2nd and 3rd thoracic and 1st abdominal seg- 

 ments; except the spiracles, eyes, some mouth parts, and 

 finally the cutaneous hairs it is otherwise colourless. 

 These three patches are apparently ordinary portions of 

 the cuticular covering that become hardened and "matured 

 at this early period for a special function, just as the 1st 

 spiracular region and some other parts are solidly chitinised 

 w'ith special objects in various Lepidopterous pupse, whilst 

 the rest of the pupal integument is still soft. These three 

 hard black patches are slightly convex and project centrally, 

 but I cannot make out that they have any sharp or 

 angular point. 



Their function is to determine the lines of rupture of 

 the egg-shell. The force used to open the egg-shell is 

 one that is in common use with many insects, especially 

 for emergence from the pupa. Here it is used for emerg- 

 ence from the egg. It is the secretion of air into the 

 interior of the larva ; the large air bubbles look as if in 

 the general body cavity of the insect, and I am not positive 

 that they are not, but as some air often escapes by the 

 mouth and anus, when the insect is flattened, I incline 

 to believe it is in the alimentary canal. The effect of 

 this air being so secreted is to enlarge the bulk of the 

 larva and exert a bursting tension in the egg-shell. If 

 this tension became sufficient the shell would burst by 

 explosion in some irregular manner, but the presence of 

 these three hard points on either side of the larva is to 

 increase the tension along a line passing along them, and 

 so, long before the strain is sufficient to produce an explo- 

 sive rupture, the egg-shell splits along each side over these 

 points. The mochcs (yperandi is in principle precisely the 

 same as that by which the pupse of the Lepidopterous 

 genera Limacodcs and Eriogastcr open their cocoons ; in these 

 a jDressure, produced by air secretion within the insect, is 

 localised as to the severest point of strain by a pupal 

 beak, and so a lid splits off at the so-determined line 



