384 BRITISH BUTTERFLIES. 



Variation of ovum. — When first laid the ova are faintly greenish, 

 soon turning to a faint green-grey, and then slightly brown, as the 

 time of hatching approaches. The eggshell is opaque and compara- 

 tively thick. The ovum hatches in from 5-24 days, depending on the 

 temperature. The ova vary greatly, but fall into two groups, those 

 with small cells, and those with a few larger ones. Those with small 

 cells are the larger ova, those with large cells are the smaller ova. 

 Diameter, -4mm. to -5mm. ; thickness, five-twelfths of diameter. (1) 

 Description of larger type of ovum. — Ovum button-shaped, i.e., like a 

 flat dome, and has the appearance of being honey-combed or sponge- 

 like. The bottoms of cells faintly greenish, and dotted and striated. 

 There are two (generally) series of intersecting lines, which are white 

 and undulating. These give rise to a series of polygons, mostly fairly 

 regular hexagons. These lines as they approach points of intersection 

 ascend and thicken, giving rise to a series of triangular pyramids. 

 Some ova, owing to the variation in size of polygons, do not have two 

 series of lines, but are marked with irregular polygons all over. Base, 

 or attached area, green and faintly cross-hatched. Micropylar area 

 appears darker green to naked eye, and is roughly polygonal and finely 

 punctured. The micropyle is surrounded by an incomplete ring of 

 very small irregular polygonal cells. Next is a fairly complete ring of 

 nine cells, mostly pentagons, one-eighth area of average cell area. 

 Then we have cells produced by the intersecting lines as above. Some 

 of these are heptagonal where they adjoin two of the ring cells. (2) 

 Description of smaller type of ovum. — The micropylar area is as above. 

 Following this are only two rings of cells, all hexagons ; in the first 

 ring, seven cells, and in the next ring, ten cells. These smaller ova 

 are thicker and more convex than the first form (J. W. Harrison). 

 These two forms of ova are figured respectively in our pi. hi., figs. 3, 4. 



Habits of larva. — Scudder says (Butts. New Engl., p. 1005) that 

 " the caterpillar makes its exit by eating only the summit of the egg, 

 where the pits are small, and separated only by thin walls ; usually it 

 feeds upon the undersurface of a leaf, and, while very young, eats little 

 holes of about its own size halfway through ; afterwards, it ploughs 

 its way through the parenchyma of either surface, making straight or 

 slightly curving grooves as wide as its own body, and several times 

 longer; when still older it devours the leaf at the edge." Harrison says 

 " the emerging larva eats a small circular hole from the apex of the 

 ovum, large enough for escape without, however, devouring the rest of 

 the egg. ,f " At first the larvae are greenish (September 5th, 1905), 

 changing later to straw-yellow (September 15th), and then to bright 

 green ; the larvae eat small irregular-shaped patches from the under- 

 side, and nearly through the sorrel leaves, leaving only the upper 

 epidermis remaining ; they cling tightly to the leaves by means of 

 their anal claspers " (Wood) ; when preparing for a moult the small 

 larvae appear always to rest on the lower side of a leaf. Buckler 

 says that the young larva is sluggish, and though it occasionally 

 eats holes through the leaves, it more generally makes a little 

 channel on the undersurface just the width of its body, and about 

 its length, so that the larva lies sunk in this channel, about on 

 a level with the surface of the leaf. It then either quits this 

 to make another similar hollow in which to rest, or else it con- 

 tinues to lengthen the channel already made, always keeping to the 



