STINGING INSECTS
The stinging insects all belong to the order Hymenoptera. In a number of families of this group the ovipositor is modified to form a sting and is connected with poison-secreting glands. We shall consider the apparatus of the honey-bee and then make briefer reference to that of other forms.
Apis mellifica, the honey bee—The sting of the worker honey-bee is situated within a so-called sting chamber at the end of the abdomen. This chamber is produced by the infolding of the greatly reduced and modified eighth, ninth and tenth abdominal segments into the seventh.[D] From it the dart-like sting can be quickly exserted.
The sting ([fig. 25]) is made up of a central shaft, ventro-laterad of which are the paired lancets, or darts, which are provided with sharp, recurved teeth. Still further laterad lie the paired whitish, finger-like sting palpi. Comparative morphological as well as embryological studies have clearly established that these three parts correspond to the three pairs of gonopophyses of the ovipositor of more generalized insects.
An examination of the internal structures ([fig. 26]) reveals two distinct types of poison glands, the acid-secreting and the alkaline-secreting glands, and a prominent poison reservoir. In addition, there is a small pair of accessory structures which have been called lubricating glands, on account of the supposed function of their product. The acid-secreting gland empties into the distal end of the poison reservoir which in turn pours the secretion into the muscular bulb-like enlargement at the base of the shaft. The alkaline secreting gland empties into the bulb ventrad of the narrow neck of the reservoir.
The poison is usually referred to as formic acid. That it is not so easily explained has been repeatedly shown and is evidenced by the presence of the two types of glands. Carlet maintains that the product of either gland is in itself innocent,—it is only when they are combined that the toxic properties appear.