Nest Expansion and the Workers
The workers are sterile female wasps. The queen releases a hormone (a pheromone) that blocks the reproductive development of the workers. If the queen dies, the workers start to develop ovaries within a couple of weeks, and can eventually lay eggs. The wasps that hatch from these eggs, however, are always males.
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For the first three or four days after they emerge, the worker wasps stay in the nest and help to feed the developing larvae. They then leave the nest to collect water and wood fibre to extend the nest. The water is used to carve out and enlarge the nest entrance. Wasps spit the water onto the area to be enlarged and mix it with the material to be disposed of to form pellets. The pellets are then carried from the nest.
Successive layers of comb are added underneath the existing layers, so that the nest grows downwards. Sometimes as many as 20 layers of comb are formed, held apart by pillars just high enough to allow the workers to get in between to feed the growing larvae. The nest envelope is extended to enclose new comb, and pockets formed within it trap air to insulate the nest and keep it warm. Wasp nests function at a temperature of 31°C. |
After working on nest-building for a while, the worker wasps switch to food gathering for up to 2 weeks. They get energy from nectar or honeydew, and, protein from insects or dead animals.
Worker wasps have very few enzymes in their guts, so they cannot digest much of the food they gather. They bring the raw food into the nest and pass it to other workers who feed the hungry larvae. In return, the larvae release a creamy blob of predigested `soup' which contains all the sustenance the worker needs. This type of food exchange is called `trophollaxic feeding', and is a key part of the social contact between workers and the developing young.
On most foraging trips the workers gather food within a few hundred metres of the nest entrance, but they can make occasional journeys up to a kilometre away. Wasps may follow one another to good food sources, but they cannot tell one another about the location of foods by dancing, as bees do. They are also forced to feed in cold or rainy weather because they do not store honey or pollen like bees.
After a period of foraging for food, the worker wasps again turn to spending most of their time in the nest, this time as guard wasps by the nest entrance. Nearly all worker wasps die before they are 3 weeks old.
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| Overwintering Nests |