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When people are sitting in a greenhouse at night with no lamp lighted, talking or smoking, they sometimes hear a smash as if a pebble had been dropped on the glass from above. It is a dytiscus beetle, whose compound eyes have mistaken the shine of the glass in the moonlight for the gleam of a pond.
Does he not even allow the admission to escape him that "the spirit of cunning and deception is transmitted"? He sees in the persecutions of the Dytiscus, the "pirate of the ponds," the origin of the faculty which the Phryganea has of refashioning its shield when demanded of it.
Kirby and Spence, on sexual differences in the length of the snout in Curculionidae; on the courtship of insects; on the elytra of Dytiscus; on peculiarities in the legs of male insects; on the relative size of the sexes in insects; on the Fulgoridae; on the habits of the Termites; on difference of colour in the sexes of beetles; on the horns of the male lamellicorn beetles; on hornlike processes in male Curculionidae; on the pugnacity of the male stag-beetle.
The claws, with which Hydrophilus seizes its prey, are, too, considerably smaller than those of Dytiscus. This larva should be kept out of the rearing ponds with just as much care as that of the more voracious D. marginalis. With the kingfisher I have already dealt at some length, so that I need say but little more with regard to it.
The larva not only of the carnivorous dytiscus but also of the vegetable-feeding water-beetle are ferocious and carnivorous, and deadly enemies of young fish and ova. In mentioning some of the Thames insecta I have also noticed some of the mollusca and crustacea. It is a pity these have not some common names. One cannot write easily of "pulmonate gasteropods." Mr. Punch.
Among the worst enemies of both ova and fry is the Dytiscus marginalis, whether this insect be in the larval or adult stage. I think that I should hardly be wrong in going even further and saying that D. marginalis is very dangerous to trout early in their yearling stage. The accompanying illustration shows a larva of Dytiscus which has caught a young trout.
Elphinstone, Mr., on local difference of stature among the Hindoos; on the difficulty of distinguishing the native races of India. Elytra, of the females of Dytiscus Acilius, Hydroporus. Emberiza, characters of young. Emberiza miliaria. Emberiza schoeniclus, head-feathers of the male. Embryo of man; of the dog. Embryos of mammals, resemblance of the. Emigration.
My whole batch was devoured one year by "devils" the larvæ of Dytiscus marginalis, the Plunger beetle. I have benefited, or at least have puzzled my neighbours also by introducing to them another sort of frog. Three years ago I bought twenty-five Hyloe, the pretty green tree species, to dwell in my Odontoglossum house and exterminate the insects.
It is generally advisable to avoid water-beetles, as most of them are more likely to do harm than good, such a number of our water-beetles being carnivorous. They will probably not harm adult fish, but they will destroy ova and fry. I have known a Dytiscus marginalis kill a trout of nearly a quarter of a pound in weight.
This beetle is not, in the adult stage at least, carnivorous, but the larva, which is about half an inch longer and considerably fatter than that of D. marginalis, is carnivorous. It may be told from the larva of Dytiscus not only by its size, which is hardly a reliable point for discrimination, but by the smaller size of the head in comparison to the rest of the body.
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