and a little coloured oil. It may be placed in boiling water without undergoing any change; the most highly concentrated acids are required to dissolve it. Except in one instance, (the female of the great aquatic beetle. Hydrous piceus,) this secretion is found only in larvæ, and in these the spinneret is usually situate in the mouth; but in the larvæ of Myrmelion it is in the opposite extremity of the body, like the spinning apparatus of spiders. This is likewise its position in the beetle just alluded to.
To the secretion of poison, and the beautifully constructed instrument by which it is injected into the body of an enemy, insects are indebted for one of the most effectual means of defence which has been assigned to any kind of animal. It is limited to the Hymenoptera, and among these we are most familiar with its effects in bees and wasps. The poison is contained in a round or ovate bladder, lying very near the hinder extremity of the abdomen, and is discharged into the sting by a narrow duct. It is secreted by two very slender twisted vessels, which sometimes unite (as in the hive-bee. Apis mellifica,) into one tube at a little distance from their insertion into the bladder. The fluid is sharp and corrosive, and it is unnecessary to refer to the experiments of Reaumur to prove that it is the cause of the inflammation and pain attending a puncture of the sting. The mere mechanical division of the tissues by so fine a point, would occasion comparatively little of either, as may be ascertained by making a puncture in the hand with a needle. The venom is a trans-
