An aberration known as testudo has the black spots of the fore wings united, and forming blotches on the front and inner areas; the ground colour of the fore wings is lighter, and the hind wings are blacker. This form occurs at large on the Continent, but it is rare; it has also been produced in the course of temperature experiments.
The only eggs of this butterfly that I have been able to obtain are the batch figured on Plate [34.] These were purplish with whitish ribs, but no caterpillars hatched from them. Hellins, who squeezed a few eggs from a freshly killed female, states that the colour apparently is a dull green. The ribs vary from seven to nine in number.
The caterpillar in the adult stage is black, with a speckled dark ochreous band traversed by a black central line on the back; the sides are dappled with ochreous grey; the under parts are brown dappled with darker, and merging into the black. The spines are dark ochreous tipped with black, and the head is shiny black and bristly. (The figure is after Buckler.)
These caterpillars live in large companies, often at the top of a high elm tree, from which they may be dislodged by a well-aimed stick, if this happens to be heavy enough to jar the branch when it reaches the mark. Besides elm trees (Ulmus), they also may be found on willow and sallow (Salix), aspen and poplar (Populus), white-beam (Pyrus aria), and various fruit trees, especially cherry. Occasionally they have been found on nettle, but the butterflies from these were small in size. June is the best month for them.
Pl. 34.
Large Tortoiseshell.
Eggs, natural size and enlarged; caterpillar and chrysalis.