Fig. 31.
The Clouded-Yellow Butterfly (Colias Edusa).
“Several other kinds of insects,” said Mr. Merton, “have the same peculiarity. Some years cockchafers are so abundant as to be quite a pest, though, perhaps, the next season they are rarely to be met with. Entomologists have been puzzled to account for these changes; but with regard to the butterflies, their abundance or scarcity is said to depend chiefly on the number of ichneumons.”
“Ichneumons!” cried Agnes, “I thought they were only found in Egypt.”
“I do not mean the animal that destroys the eggs of the Crocodile on the banks of the Nile,” said Mr. Merton, “but a kind of fly which lays its eggs in the living bodies of caterpillars.”
“Ah!” said Agnes, “I think you have told me of this fly before, mamma. I remember it now.”
Fig. 32.
Ichneumon Fly on a Floret of the Flowering Rush.
“Yes,” said Mrs. Merton, “I remember describing to you the Ichneumon that lays its eggs in the caterpillar of the Cabbage Butterfly; but there are several kinds, and there, I think, is one quite distinct hovering round the florets of that Flowering Rush.”
She told the driver to stop; and Agnes distinctly saw the Ichneumon her mother had alluded to.
They now passed a pretty little cottage with a large myrtle trained against it; and Mrs. Merton remarked how very few similar specimens they had seen of the mildness of the climate. “I remember, when I was a girl,” said she, “having heard so much of the myrtles of the Isle of Wight, that I expected to find the whole island a complete green-house; but, the fact is, we have seen much fewer myrtles here than we did last year in Devonshire.”