AGKIADES THETIS. 359 



on which she rested ; so intent was she upon her work that the 

 observer was able to get within 18 inches of her, and was thus enabled 

 to distinctly see her abdomen thrust out to its fullest extent, curved 

 slightly under so as to reach the underside of one of the smaller leaflets 

 near the centre of the plant, and observe the working of the terminal 

 segments during the operation of extruding the egg, but was not in 

 such a position as to see the egg actually attached to the leaf ; the 

 plant, however, was immediately plucked, when two eggs were found on 

 the underside of one of the leaves at the part where the butterfly had been 

 sitting, one of them evidently having been laid before the observer got 

 into position for observation, a somewhat difficult operation owing to the 

 steepness of the ground, or much more probably by another $ that had 

 paid an earlier visit to the same leaf. Chapman observes (in litt.) that, in 

 confinement, the species lays freely, usually choosing the undersides of 

 leaves, petioles, and stems, low down near the ground; under such 

 circumstances, the choice being limited, the same spot is often 

 attractive to all the butterflies caged and to the same one on more than 

 one occasion, so that one finds eggs laid, as it were, in patches and 

 other places bare, although, as a matter of fact, the habit of the species 

 is to lay its eggs singly ; an egg has been found even on the petal of a 

 flower, but this was quite obviously due to the choice of place being 

 too restricted. Eecently we caged up some $ s (September, 1909) but 

 only three eggs were laid, one on the upperside of a leaflet (towards 

 the apex), one on the underside of a leaflet, and one on the side of a 

 petiole. " s Wood observes (in litt.) that, in confinement, he found the eggs 

 attached chiefly to the underside of the leaves^ a few only on the 

 upperside, and fewer still on stems, in nature all that he has ever found 

 have been laid on the underside of leaves; Wood further notes that 

 he has found difficulty in obtaining eggs in confinement until he has 

 introduced Lasius flavus, when the ? s have laid readily. This, how- 

 ever, is evidently, from Chapman's experience, not at all necessary. 

 The length of the egg- stage varies according to the time of year, 

 temperature, etc., e.g., eggs laid May 28th, 1896, at Reigate, hatched 

 June 6th = 9 days; eggs laid June 6th, 1899, at Reigate, hatched 

 June 17th = 11 days (Prideaux) ; eggs laid September 18th, 1909, in 

 London, hatched October 9th = 18 days (Tutt). 



Ovum. — The egg is green in colour, with a covering of white 

 sculpturing, that makes it look more or less white, according to 

 whether one sees most of the white accretion or looks in its meshes on 

 the green egg within. The diameter in different eggs and different 

 batches varies from 0'60mm. to 0*65mm. (these differences give a cubic 

 difference of about 7:9), but may be taken to average about 0*6 lmm. ; 

 this measurement is to the outside of the white coating, the actual egg 

 being about 0'54mm. ; the height is similarly # 27mm. or 0'24mm. 

 The egg is of the usual cheese-shape, flat top and bottom, rounded 

 round the margins; in a diameter of 0-58mm., the flat top is - 46mm. 

 across. On a top view one notes the central micropylar depression, 

 depression because without any of the white accretion; it is about 

 0-07mm. across, and has a central rosette of 8 to 10 cells, and round 

 this two rows of cells, the outer the larger ; this, however, is only 

 broadly so, as the cells are not arranged in exact rows and circles, and, 

 of the outer ones, one or two of the larger seem to belong properly 

 to those covered by white accretion and one or two curved ones seem 



