Brachygastra mellifica

In general, external reproductive organs can distinguish males from females; only females have stingers. Workers and males share the same coloration. They both have alternating abdominal bands of yellow and black. Queens characteristically have a dark reddish-brown abdominal coloration. Queens can also be distinguished from workers due to the occurrence of sperm in the spermathecae of the queens.[5] This species is small with a body length of 7-9 mm.[3]

Brachygastra mellifica make paper nests that range in size from 40–50 cm in diameter. These nests are quite full and can house anywhere from 3,500 to 18,700 wasps.[3] The nest begins as a single irregular layer of cells attached to the first layer of carton on a branch. Clumps of cells on the branch are then extended into the first hanging layer. Successive layers are formed independently and extend out and around the bottom of the first layer. This happens multiple times around and over the previous layer, resulting in a growing spiral. The nest goes from a small, flat oval to a sausage- or capsule-like shape over time. The surface of the nest is blotchy, colored brown or grey, varying as a result of the raw materials used for construction. The texture of the surface is that of rough cardboard, and is not glossy.[6]

Queens within a single colony are highly related, which is consistent with the hypothesis that queens are only produced when the colony contains one queen. In a study on kin selection and relatedness the worker wasps were considerably more related to the queens than to other workers. On average, workers have an r=0.37 for relatedness to queens.[5]

B. mellifica genetics show high levels of relatedness among workers despite the large number of queens per colony. R=0.23 for all workers to each other, which is significantly lower than the relatedness of workers to queens.[5] Genetic relatedness was determined in the study using PCR. DNA microsatellites are good genetic markers for studying relatedness due to their Mendelian behavior and high variability. DNA was sampled from the whole wasp, thorax and head, or thorax alone in this study.[5]

The split-sex ratio is a result of the asymmetrical relatedness between brothers and sisters, since B. mellifica are haplodiploid. When there are many queens, males are produced. Since workers can share a maximum of 3/4 of their genes with sisters, they favor caring for female siblings over male siblings, who only share a maximum of 1/2 of their genes. Since this wasp follows a cyclical monogynous pattern, there is increased relatedness among all of the progeny. The split-sex ratio is the most distinct in any swarm-founding wasp currently studied.[5] Research done on kin selection and relatedness showed that queens produce the eggs that become males, not workers. Workers 'police' each other to make sure the queens produce most, if not all, of the males.[5]

Brachygastra mellifica is very good at searching and feeding on Diaphorina citri in tree flushes, an introduced species that has become one of their major prey items. These wasps feed not only on the fluids from the prey, but may also eat the entire exoskeleton of D. citri. They also may consume larvae of the weevil Anthonomus aeneoulus and a moth from the family Alucitidae.[7] Trophallaxis, or regurgitation, has also been observed on the nest surface of the Mexican honey wasp, in which the forager regurgitates a drop of nectar to a responsive wasp.[6]

Diogmites angustipennis is a robber fly known to prey on honeybees that has been observed preying on B. mellifica. Orb-weaving spiders have also been known to take single wasps as prey outside the nest. Attacks on the entire nest are also common. Both opossums and golden-fronted woodpeckers have been seen dissecting a nest. Other dismembered nests have damage that is similar to the damage caused by the woodpeckers to the nests.[6]

It is thought that wasps and stingless bees were the first pollinators of the avocado, before the introduction of the European honeybee to the Americas. Brachygastra mellifica are pollinators because when they collect food for their larvae; they carry much pollen on their hairy head – including avocado pollen. They also carry pollen on their thorax and legs, and inside their unique thoracic cavities. While many other wasp species visit avocado flowers, they contribute less to pollination due to lower visitation rates and/or carrying less pollen on their bodies.[8]

It has been suggested that B. mellifica can be used as a natural biological control agent.[6] They offer many features, such as the ease of which the nests can be moved, the speediness of population growth, and the fact that closed system preservation is possible. One pest species of particular interest to scientists is Diaphorina citri, a very destructive pest of Citrus trees, which carries bacteria that make the fruit inedible and slowly kill the trees (citrus greening disease).[7] Diaphorina citri is a major prey of B. mellifa and it would be beneficial to use these wasps to attack these pests.

B. mellifica is one of few insects besides bees to create and store their own honey. Chromatographic analysis of B. mellifica honey showed 6/7 of the same peaks that appeared in honeybee mesquite honey. Melibiose is the only peak that did not occur in both honeys. Both the glucose and fructose content in B. mellifica honey are comparable to that of honeybee mesquite honey. The similarities in the two honeys substantiate the idea that these are foraging wasps, because honey stores come from multiple common floral sources, such as mesquite and sunflower.[6]

Brachygastra mellifica serve as a food source for the Popoloca Town of Los Reyes Metzontla, Mexico. The Popolucas have at least 17 species of insects in their diet, including B. mellifica and other wasps. The Spanish local name for this delicacy is "Panal Miniagua", and the Popoluca name is "Cuchii". They eat the honey and larvae of these wasps year round, but only harvest when the moon is between its last quarter and waning gibbous. According to traditional knowledge and experience, the nests are full of honey and larvae at this time. These insects can be cooked and eaten with salsa and tortillas.[9]