Pl. 67.
Heath Fritillary.
Eggs, natural size and enlarged; caterpillar (after Buckler), and chrysalis.
Kane (Catalogue of the Lepidoptera of Ireland), referring to this species, remarks: "This butterfly has been known to increase so prodigiously that whole fields and roads became blackened by the moving myriads of larvæ. An instance of this was observed by the Rev. S.L. Brakey, near Ennis, Co. Clare, where he drove out to see a reported 'shower of worms,' and found as above described, the larvæ being so multitudinous in some fields that the black layer of insects seemed to roll in corrugations as the migrating hosts swarmed over each other in search of food. The imagines that resulted from the starved survivors were extremely small and faded in colour."
These caterpillars are destroyed in great numbers by Hymenopterous parasites, chiefly Apanteles, and it is almost certain that a large percentage of those collected will prove to have been stung.
The butterfly is on the wing in May and June, and seems to affect damp meadows, marshy ground on the sides of hills, and such kind of places. It does not necessarily occur wherever its food-plant is abundant, but scabious is always found to be present in the haunts of the butterfly; so if we know that the insect occurs in a particular district we should probably get a clue to its exact whereabouts by noting the likely places in that district where the food-plant flourishes.
Although it has seemingly disappeared from various English localities where it was formerly common, the butterfly may be found in many parts of the British Islands, but it is local and does not occur northwards much beyond the Caledonian Canal.
Abroad it spreads over Europe to Northern Africa, and its range extends eastward through Asia to Amurland and Corea.