By Wolfgang Bucherl
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Extra resources for Venomous Animals and their Venoms. Venomous Invertebrates
The interior of the sting bulb of the bee is rather complicated. In it the venom duct can be closed and opened by means of a locking apparatus (Trojan, 1922). The venom channel into the bulb narrows to a thin horizontal cleft which is normally almost shut. Two closing muscles originating at its dorsal side and inserted downward in the bulb are able to pull down the roof of the cleft and in that way shut it completely. A thick muscle inserted at the ventral side of the cleft opens, when contracted, by pulling down its underside (Trojan, 1922) so that the venom can be pumped through.
It is directed against the largest enemies of the honeybee, against honey- and brood-robbing mammals and birds. The following facts demonstrate this. As already mentioned (see Table II), the sting apparatus of the honeybee worker possesses a series of peculiarities in comparison to the more primitive queen bee sting and to those of solitary bees. The sting possesses a preformed breaking point: the spiracular plates and muscles which in the queen bee prevent the loss of the sting are reduced strongly in the worker.
The function of the single gland parts is still unknown. The gland system may be very large. In Formica ruf a its length is two thirds that of the gaster length. Queen glands are smaller than those of the workers. 4. The Dufour Gland Dufour (1841) described another gland at the sting apparatus, ventral to the venom gland. It can be found generally in the Apocrita (Forel, 1878; Bordas, 1895; Pawlowsky, 1927; Heselhaus, 1922). In the Symphyta a homologous gland seems to exist (Robertson, 1968). The Dufour gland is of a more simple structure than the venom gland and consists of a simple tube which secretes and stores its products at the same time.