10 Mr. G. C. Champion and Dr. T. A. Chapman's 



length. The egg-shell retains the form of the egg and 

 its surface presents a fine hexagonal network. 



The difference is thus great between 0. tristis and the 

 other species, but physiologically it is less than at first 

 sight appears. The egg that 0. tristis lays is not strictly 

 speaking an egg, i. e. a mass of germinal and food material 

 that will develop into a larva, it is really a larva enclosed 

 in an egg-shell. When the egg is laid, the larva within is 

 very plain, and though otherwise colourless, jaws, spiracles, 

 and eye-spots are conspicuous. 



It is obvious, therefore, that the egg is fertilised, some 

 considerable period before it is laid, and that development 

 goes on in the interval, precisely as in 0. vittigera and 0. 

 cacalize, and there is no reason to doubt, in precisely the 

 same way, that is, whilst the eggs are still in the ovarian 

 tubes. My beetle only laid a few eggs and then died ; I 

 should imagine, these were the last of a long series similar 

 to those of 0. vittigera. 



It may be well to mention what we observed of the 

 habits of the larvae before entering on the characters of 

 those of each species. 



When first laid or hatched the larvse inflate themselves 

 with a certain amount of air, and increase considerably in 

 size. This seems to be a common occurrence in insects, 

 and seems to be necessary to secure tension of the dermis 

 to give a fulcrum for muscular action, when such tension is 

 not obtained by fat, or food in the alimentary canal or 

 other solid material. 



The only larvae we saw much of at large were those of 

 0. vittigera, and in a less degree 0. cacalise. 



Where the young larvae of 0. vittigera are laid, there 

 they nibble a circular hole in the leaf, and amongst a mass 

 of the food-plant, leaves with numerous small circular 

 holes show where larvae have been laid. The parent 

 beetles eat a great deal, but they nearly always eat from 

 the edge of the leaf. 



At the end of the first week of July, there were already 

 a good many young larvae, judging by the holes in the 

 leaves, and there were none of any size, so that egg (?) lay- 

 ing does not begin till July. But we were at first puzzled 

 about the larvae, because we could not see any at all, 

 except a few newly laid ones. We found, however, that 

 after their first meal, they went off to hide in the growing 

 heads of the Peucedanum. When the flowering stem is, 



