it constructs its web and silken cord as already described (page 36), and then changes to a bluish-white chrysalis, dotted with black. The butterflies of the summer brood emerge shortly after, but the chrysalides of the next brood hybernate till the following spring.
It is remarkable that we are so plagued with 'Whites' seeing that they have so many enemies. Many of the insect-feeding birds commit fearful havoc among their larvæ, and often chase the perfect insects on the wing, but perhaps their greatest enemy is the ichneumon fly.
Look under the ledges of a wall of any kitchen garden, and you will see little clusters of oval bodies of a bright yellow colour. Most gardeners know that these are in some way or other connected with the caterpillars that do so much damage to their vegetables. They are often considered to be eggs laid by the larvæ, and are consequently killed out of pure revenge, or with a desire to save the crops from the future marauders.
No greater mistake could be made. These yellow bodies are the silken cocoons of the caterpillar's own foes. They contain the pupæ of the little flies whose larvæ have lived within the body of an unfortunate grub, and, having flourished to perfection at the expense of their host, left its almost empty and nearly lifeless carcase to die and drop to the ground just at the time when it ought to be working out its final changes. Often you may see the dying grub beside the cluster of cocoons just constructed by its deadly enemies. Should you wish to test the extent of the destructive work of these busy flies, go into your garden and collect a number of larvæ, and endeavour to rear them under cover. The probability is that only a small proportion will ever reach the final state, the others having been fatally 'stung' before you took them.
The Small White (P. Rapæ)
This butterfly closely resembles the last species except in point of size. The male, represented on [Plate I] (fig. 4), has a dark grey blotch at the tip of each fore wing, a round spot of the same colour beyond the centre of that wing, and another on the costal margin of the hind wing. The female may be distinguished by an additional spot near the anal angle of the fore wing.
Although this and the two other common butterflies (Brassicæ and Napi) that frequent our kitchen gardens are usually spoken of
as 'Whites,' a glance at a few specimens will show that they are not really white at all, but exhibit delicate shades of cream and yellow, inclining sometimes to buff. The under surfaces are particularly noticeable in this respect, for here the hind wings and the tips of the fore wings display a very rich yellow.
The species we are now considering is also very variable both in its ground colour and the markings of the wings. The former is in some cases a really brilliant yellow; and the latter are in some cases entirely wanting.
Rapæ is double-brooded, the first brood appearing in April and May, and the other in July and August.