The venom gland in social wasps. Comparison with the gland of the honeybeeand fat cells as possible source of venom precursor molecules

The venom gland in social wasps is both the source of their venom and of th eir alarm pheromones. As is the case in most ante, the venom reservoir cont ains a secretory region within, known as the convoluted gland. In contrast with ants (venom gland with one single free tubule), the venom gland in was ps contains two free tubules. Our new observations deal with the associatio n of the so-called << free tubules >> with fat cells. The association of th ese tubules and the fat body is already very obvious during the pupal stage . Although the morphology of the venom gland in the honeybee is totally diffe rent from that of social wasps. the painfulness and lethal activity of thei r venoms are comparable. These facts allow us to conclude that the elaborat ion of additional structures within the venom reservoir is not necessary fo r the production of toxic, painful or lethal compounds. The functional mean ing of the convoluted gland should hence be searched for in a different dir ection. An interesting aspect is that a convoluted gland has been found als o in pompilid wasps, in eumenids and probably also in their ancestors. In t his regard they differ strongly from honeybees land some other taxa). Based upon histochemical research, we postulate that the origin of the convolute d gland is a consequence of the functional needs to produce pheromones with in the same gland as the one that produces the venom itself, in combination with strongly muscular reservoir walls and in combination with the absence of sting autotomy. Contrarily, scarce venom reservoir musculature and stin g autotomy are typical for honeybees.