Belonogaster petiolata

Several factors appear to contribute to brood decline and the end of the colony cycle in B. petiolata. These include: cessation of the supply of solid food to colonies and larvae during the reproductive phase, a decrease in the worker/larva ratio during the latter phase due to the slow loss of workers, increasing the number of gynes and males, and an adult priority over food reception from foragers. The brood gets aborted to feed hungry adults. Eventually, the brood declines and the adults leave the nest.[2] Usually, some cell demolition is done by the queen in post emergence colonies.[3]

The workers carry out nearly all the basic work, like creating and fixing damage to the nest, getting food, and feeding the larvae. The queen's primary job is to lay eggs. When there is an active queen, workers often have undeveloped ovaries. However, when the queen is removed, 11% of workers develop mature ovaries. This is reproductive suppression under the power of the queen. If there are any eggs found that are not laid by the queen, she eats them (oophagy).[3] Most of these eggs were likely laid by subordinates. Queens often get to rest in the central areas of the nest close to the growing larvae while subordinates and workers often position themselves in the outer areas of the nest.[3]

The queen creates a dominance hierarchy by initiating dominant interactions. These include biting, hooking, and soliciting. In hooking, females grasp subordinates and hang from them in a hook like formation while receiving regurgitate. The queen often displays these behaviors to assert her dominant status to the other wasps. In soliciting, the dominant female approaches the other female with her antennae outstretched and antennates her head, especially her mouthparts. The other females respond by ignoring the soliciting, remaining immobile in a submissive way until the other wasp leaves, or by soliciting back.[3] Sometimes the queens initially exhibit dominance behaviors, but then move to the top of the nest and become more inactive towards the end of the colony cycle. Other times, the queens are always dominant throughout the whole cycle. Females usually direct their dominance behaviors at the females directly below them in the dominance hierarchy.[3] The queens are the most aggressive females in the nest, so receive fewer threats.

Sometimes, a queen or another female will eat eggs laid in her own colony. The majority of the time she eats the eggs of her subordinates, however, a female may occasionally eat her own eggs. Queens also undertake egg inspections to see if the eggs in the nest are their own or if they were laid by a subordinate. The majority of oophagies are committed by the queen (87.5%). Oviposition is the laying of eggs. Queens lay 83.3% of the eggs in pre-emergence colonies, which is a significantly higher rate of oviposition than that of subordinates. Workers were never observed eating or laying eggs.[3]

The larval saliva of B. petiolata contains many amino acids and nutrients that are useful for adult wasps. Females who are looking to lay eggs solicit larvae in order to receive some salivary fluid so they can gain some nutrients before laying the eggs. To do this, females undergo trophallaxis with the larvae. The larvae are first fed masticated food by the females wasps and then in return, the larvae produce salivary fluid. Usually, the wasps prompt the larvae to produce this salivary secretion by antennating a larva's head and vibrating its body. The larva then extends its head and produces a drop of clear saliva. Adults wasps prefer to solicit older larvae for trophallaxis, likely because they expect to receive more saliva from older larvae than from younger larvae. Sometimes, body vibrations of soliciting adults become synchronized and this seems to excite the larva in a positive way.[3]

There is a caste system within the B. petiolata colonies. There are physiological and morphological differences between worker castes and reproductive castes. Foundresses and gynes (reproductive caste) are generally larger than workers. When workers are first born their body size is much smaller than gynes and foundresses, but later in the colony cycle, their size grows more similar to gynes. Foundresses and gynes have larger ovaries and more fat content than workers do. Workers have broad heads, while the reproductive caste wasps have broader thoraces and gasters.[6] Typically, foundresses are larger than their subordinates. Also, about 98% of queens (foundresses) and 95% of gynes are found to be inseminated, while workers are not. They have immature ovaries that do not function in the presence of an active queen. When there is no active queen, about 11% of workers develop mature ovaries. Active queens are the primary egg layers in colonies and possess well-developed ovaries.[6] Differentiation of castes sometimes occurs early during larval development, or it can happen during the later adult stage due to differing social communications and adult nutrition. A wasp's ability to survive winter, and its number of fat reserves, has been used to distinguish gynes from workers. Fat content is an indicator of caste.[6]

The dominance of the queen over the colony keeps the subordinant nature of worker wasps intact. When a queen dies, however, an older alpha worker, that was likely present when the colony was younger, often takes up the dominant position. The loss of a queen is also associated with the development of ovaries in 11% of worker wasps and in many alpha workers. During the pre-matrifilial stage, in colonies of B. petiolata, removal of the queen led to her replacement by the second most dominant foundress, who is known as a beta-foundress, instead of a worker.[2]

Mating occurs when a male wasp approaches a female, and the two undergo mutual or unilateral antennation, where the pair touches each other's antennae or the male probes the female's thorax and abdomen with his antennae. Then, the male mounts the female and begins to establish genital contact by touching the female's abdomen with his own. Copulation only lasts about five seconds.[7]

The ovarian width of gynes increased from April to July which is within the overwintering period. From July through August, mean ovarian width of overwintering females increased sharply, and then fell between late August and September.[5] The percent of gynes with mature oocytes in their ovaries increased from 2.9% in April to 15.6% at the end of July, and then lastly to 45.7% in August. Female wasps with larger ovaries are more likely to lay eggs. Workers have thin, inactive ovaries that prevent them from ovipositing.[6]

Workers are rarely, if ever, inseminated. None of the workers from pre-matrifilial and matrifilial colonies were observed by Keeping, M.G. (2002) to be inseminated. Overwintering gynes from Sterkfontein cave had the highest percent insemination. Lack of insemination has frequently been used as a criterion for distinguishing queens from workers in social wasps. All queens and nearly 98% of subordinate foundresses were inseminated.[6] Workers may not be inseminated because they emerge over the period of the colony cycle when males are absent. Inseminated daughters were only recorded from late February onwards, coinciding with the period of male production. Of course, inseminated individuals are more likely to lay eggs and are seen as part of the reproductive caste.[6]

Gynes and other female wasps have mate recognition signals, or pheromones, within their venom, thorax and heads. This causes males to be attracted to them. The pheromones within the venom seem to be very strong compared to pheromones from the thorax and head. These pheromones are often spread all over the body during grooming, further increasing the females' attractiveness to males.[7][8]