OF INSECTS. 107 



and a little coloured oil. It may be placed in boil- 

 ing 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 larvae, and in these the spinneret 

 is usually situate in the mouth ; but in the larvae 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 in- 

 flammation 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-. 



