The majority of butterfly chrysalides are naked, and of an angular form, some being remarkable for the brilliancy with which they are spotted with gold and silver.
The Vanessa family is an example of this, the Vulcania and Huntera being especially brilliant.
Caterpillars of the “Skipper” family make a web-like covering of silk for the reception of the chrysalides, but there has been hitherto only one species of this family found in Teneriffe.
Many caterpillars of various kinds kept during the winter months were very subject to the raids of the Ichneumon fly. This fly lays its egg on the larva, and it is not easily perceived on the animal unless looked for through a magnifying-glass.
The caterpillar lives on, and seemingly thrives, but after it has turned to its pupa state the fly develops, and a fine Ichneumon fly appears in the breeding-cage instead of the expected butterfly. There are large and small varieties of this fly, the former laying only one or two eggs on the caterpillar, the latter a great many, and they emerge from the chrysalis in corresponding numbers.[1] The only remedy seems to be to inspect all larvæ through a magnifying-glass, and to reject any infected specimens. Pieris Cheiranthi is particularly liable to this fly. The red fungus found on the Tithymali moth caterpillar is another disease, but is not very common.
[1]This occurrence is mentioned by Gilbert White in his “Natural History of Selborne,” v. “Observations on Insects and Vermes,” p. 519. Ed. 1813.
Caterpillars should be handled as little as possible while removing them to their fresh food. As a rule, they crawl on to the fresh supply at once, but in the case of very small specimens a camel-hair brush should be used to lift them from one place to another. Many of them emit a fluid when touched. The Tithymali spits out a quantity of green fluid when disturbed.
Butterflies generally seem to be found in the greatest numbers in the barrancos early in the year. When, however, the fields get green and vegetation increases, they desert the barrancos and take more to the fields and country, with the exception of the Argynnis Lathonia, a variety which more particularly frequents barrancos.
The time of appearance of all species takes place from two to four weeks later the higher they are up the mountains. The south part of the island is not so fertile a place for Lepidoptera as the north; perhaps this is owing to the more sparse vegetation on that side.