Queen signals in a stingless bee: suppression of worker ovary activation and spatial distribution of active compounds.

In most species of social insect the queen signals her presence to her workers via pheromones. Worker responses to queen pheromones include retinue formation around the queen, inhibition of queen cell production and suppression of worker ovary activation. Here we show that the queen signal of the Brazilian stingless bee Friesella schrottkyi is a mixture of cuticular hydrocarbons. Stingless bees are therefore similar to ants, wasps and bumble bees, but differ from honey bees in which the queen's signal mostly comprises volatile compounds originating from the mandibular glands. This shows that cuticular hydrocarbons have independently evolved as the queen's signal across multiple taxa, and that the honey bees are exceptional. We also report the distribution of four active queen-signal compounds by Matrix-assisted laser desorption/ionization (MALDI) imaging. The results indicate a relationship between the behavior of workers towards the queen and the likely site of secretion of the queen's pheromones.

Nest thermoregulation in Polybia scutellaris (White) (Hymenoptera: Vespidae).

Polybia scutellaris (White) builds large nests characterized by numerous spiny projections on the surface. In order to determine whether or not the nest temperature is maintained because of homeothermic conditions of the nest individuals or otherwise, we investigated the thermal conditions within the nests built by P. scutellaris. We measured the temperature within active and abandoned nests. The temperature in the active nest was almost stable at 27°C during data collection, whereas the temperature in the abandoned nest varied with changes in ambient temperature. These results suggest that nest temperature was maintained by the thermogenesis of the individuals of the colony. This is the first report of nest incubation caused by thermogenesis of species of Polybia wasps.

The acceptance rate of young wasps by alien colonies depends on colony developmental stages in the swarm-founding wasp, Polybia paulista von ihering (Hymenoptera: Vespidae)

In social insects, newly emerged individuals learn the colony-specific chemical label from their natal comb shortly after their emergence. These labels help to identify each individual's colony of origin and are used as a recognition template against which individuals can discriminate nestmates from non-nestmates. Our previous studies with Polybia paulista von Ihering support this general pattern, and the acceptance rate of young female and male wasps decreased as a function of their age. Our study also showed in P. paulista that more than 90 percent of newly emerged female wasps might be accepted by conspecific unrelated colonies. However, it has not been investigated whether the acceptance rate of newly emerged female wasps depends on colony developmental stage of recipient colonies. We introduced newly emerged female wasps of P. paulista into different colony developmental stags of recipient colonies, i.e., worker-producing and male-producing colonies. We found that the acceptance rate of newly emerged female wasps by alien colonies was pretty lower by male-producing colonies than worker-producing colonies. This is the first study to show that the acceptance rate of young female wasps depends on stages of recipient colonies.

Nest thermoregulation in Polybia scutellaris (White) (Hymenoptera: Vespidae)

Polybia scutellaris (White) builds large nests characterized by numerous spiny projections on the surface. In order to determine whether or not the nest temperature is maintained because of homeothermic conditions of the nest individuals or otherwise, we investigated the thermal conditions within the nests built by P. scutellaris. We measured the temperature within active and abandoned nests. The temperature in the active nest was almost stable at 27°C during data collection, whereas the temperature in the abandoned nest varied with changes in ambient temperature. These results suggest that nest temperature was maintained by the thermogenesis of the individuals of the colony. This is the first report of nest incubation caused by thermogenesis of species of Polybia wasps.

The acceptance rate of young wasps by alien colonies depends on colony developmental stages in the swarm-founding wasp, Polybia paulista von ihering (Hymenoptera: Vespidae).

In social insects, newly emerged individuals learn the colony-specific chemical label from their natal comb shortly after their emergence. These labels help to identify each individual's colony of origin and are used as a recognition template against which individuals can discriminate nestmates from non-nestmates. Our previous studies with Polybia paulista von Ihering support this general pattern, and the acceptance rate of young female and male wasps decreased as a function of their age. Our study also showed in P. paulista that more than 90% of newly emerged female wasps might be accepted by conspecific unrelated colonies. However, it has not been investigated whether the acceptance rate of newly emerged female wasps depends on colony developmental stage of recipient colonies. We introduced newly emerged female wasps of P. paulista into different colony developmental stags of recipient colonies, i.e., worker-producing and male-producing colonies. We found that the acceptance rate of newly emerged female wasps by alien colonies was pretty lower by male-producing colonies than worker-producing colonies. This is the first study to show that the acceptance rate of young female wasps depends on stages of recipient colonies.

Chemical signals in the stingless bee, Frieseomelitta varia, indicate caste, gender, age, and reproductive status.

Chemical compounds on the cuticle are a rich source of information used during interactions among social insects. Despite the multitude of studies on these substances and their function in ants, wasps, and honeybees, little is known about this subject in stingless bees (Hymenoptera: Apidae, Meliponini). We studied the chemical composition of the cuticle of the stingless bee, Frieseomelitta varia, by gas chromatography-mass spectrometry (GC-MS), to investigate potential chemical variation among castes, gender, age, and reproductive status. We found differences in the cuticular hydrocarbon composition among workers, males, and queens, recording both qualitative and quantitative differences among individuals of different ages and gender. The cuticle of physogastric queens presented a chemical profile that was distinct from all other groups in the analysis, with high relative abundances of alkenes and alkadienes with 27, 29, and 31 carbon atoms. We discuss the possibility that these compounds signal a queen's presence to the colony, thereby initiating all vital worker-queen interactions.

Decision rules for egg recognition are related to functional roles and chemical cues in the queenless ant Dinoponera quadriceps.

The capacity to distinguish colony members from strangers is a key component in social life. In social insects, this extends to the brood and involves discrimination of queen eggs. Chemical substances communicate colony affiliation for both adults and brood; thus, in theory, all colony members should be able to recognize fellow nestmates. In this study, we investigate the ability of Dinoponera quadriceps workers to discriminate nestmate and non-nestmate eggs based on cuticular hydrocarbon composition. We analyzed whether cuticular hydrocarbons present on the eggs provide cues of discrimination. The results show that egg recognition in D. quadriceps is related to both age and the functional role of workers. Brood care workers were able to distinguish nestmate from non-nestmate eggs, while callow and forager workers were unable to do so.

The look of royalty: visual and odour signals of reproductive status in a paper wasp.

Reproductive conflicts within animal societies occur when all females can potentially reproduce. In social insects, these conflicts are regulated largely by behaviour and chemical signalling. There is evidence that presence of signals, which provide direct information about the quality of the reproductive females would increase the fitness of all parties. In this study, we present an association between visual and chemical signals in the paper wasp Polistes satan. Our results showed that in nest-founding phase colonies, variation of visual signals is linked to relative fertility, while chemical signals are related to dominance status. In addition, experiments revealed that higher hierarchical positions were occupied by subordinates with distinct proportions of cuticular hydrocarbons and distinct visual marks. Therefore, these wasps present cues that convey reliable information of their reproductive status.

Promotion of thermoregulatory insulation in nests of neotropical wasps by building extra-combs with empty cells.

We examined the hypotheses that the empty combs of Polybia occidentalis Olivier (Hymenoptera: Vespidae) nest insulate the inside of the nest. To examine this hypotheses, two kinds of temperature measurements were carried out: 1) with the outer comb of the nest intact (Control) and 2) removed (Treatment), using a large and a small nest. In the large nest, the daily nest temperatures (outer part, Tn1; inner part, Tn2) in Control were lower by 0.6 degrees C (Tn1) and 1.2 degrees C (Tn2) than those in Treatment, because of a higher ambient temperature (Ta) throughout temperature assessment in Treatment. However, the excess temperature (Tn - Ta) in Control was higher than that in Treatment. The value was higher by 0.7 degrees C at Tn1 and 0.1 degrees C at Tn2. In the small nest, the excess temperature in outer part was similar between experiments, while that in inner part of Control was lower than that of Treatment. The temperature fluctuation in the nests was lower in the Control than that in Treatment both the outer and inner part of the comb. We conclude that the unused comb is ecologically invaluable for raising and protecting the brood from extreme changes in ambient temperature during the winter period, because it helps not only keeping a higher nest temperature but also decreasing the temperature fluctuation around the brood combs. In addition, such a high temperature may influence the performance of adult wasps.

Promotion of thermoregulatory insulation in nests of neotropical wasps by building extra-combs with empty cells / Promoção de isolamento térmico em ninhos de vespas neotropicais pela construção de favos com células vazias

We examined the hypotheses that the empty combs of Polybia occidentalis Olivier (Hymenoptera: Vespidae) nest insulate the inside of the nest. To examine this hypotheses, two kinds of temperature measurements were carried out: 1) with the outer comb of the nest intact (Control) and 2) removed (Treatment), using a large and a small nest. In the large nest, the daily nest temperatures (outer part, Tn1; inner part, Tn2) in Control were lower by 0.6°C (Tn1) and 1.2°C (Tn2) than those in Treatment, because of a higher ambient temperature (Ta) throughout temperature assessment in Treatment. However, the excess temperature (Tn - Ta) in Control was higher than that in Treatment. The value was higher by 0.7°C at Tn1 and 0.1°C at Tn2. In the small nest, the excess temperature in outer part was similar between experiments, while that in inner part of Control was lower than that of Treatment. The temperature fluctuation in the nests was lower in the Control than that in Treatment both the outer and inner part of the comb. We conclude that the unused comb is ecologically invaluable for raising and protecting the brood from extreme changes in ambient temperature during the winter period, because it helps not only keeping a higher nest temperature but also decreasing the temperature fluctuation around the brood combs. In addition, such a high temperature may influence the performance of adult wasps.

Examinou-se a hipótese de que os favos vazios dos ninhos de Polybia occidentalis Olivier (Hymenoptera: Vespidae) atuam como isolamento térmico dos elementos internos da colônia. Para avaliar essa hipótese dois tipos de medidas de temperatura foram tomadas: 1) com o favo externo intacto (Controle) e 2) removido (Tratamento), usando um ninho grande e um ninho menor. As temperaturas diárias no ninho grande (parte externa Tn1; parte interna Tn2), no Controle, foram 0,6°C (T n1) e 1,2°C (Tn2) mais baixas que aquelas do Tratamento, devido à temperatura ambiente (Ta) mais alta durante todo o período avaliado. Entretanto, a temperatura excedente (Tn - Ta) no Controle foi mais alta que no Tratamento. O valor foi 0,7°C mais alto em Tn1 e 0,1°C em Tn2. No ninho menor, a temperatura excedente na parte externa foi semelhante entre os experimentos, e na parte interna a temperatura do Controle foi inferior à do Tratamento. A flutuação térmica nos ninhos foi menor no Controle que no Tratamento, tanto na parte externa quanto interna dos favos. Conclui-se que o favo sem uso é ecologicamente muito importante para criar ou proteger a cria das alterações extremas de temperatura ambiente no inverno, uma vez que ele auxilia na manutenção de temperatura alta no ninho e também no decréscimo da flutuação de temperatura ao redor dos favos de cria. Além disso, essas temperaturas mais altas influenciam as atividades dos adultos.

Thoracic vibrations in stingless bees (Melipona seminigra): resonances of the thorax influence vibrations associated with flight but not those associated with sound production.

Bees generate thoracic vibrations with their indirect flight muscles in various behavioural contexts. The main frequency component of non-flight vibrations, during which the wings are usually folded over the abdomen, is higher than that of thoracic vibrations that drive the wing movements for flight. So far, this has been concluded from an increase in natural frequency of the oscillating system in association with the wing adduction. In the present study, we measured the thoracic oscillations in stingless bees during stationary flight and during two types of non-flight behaviour, annoyance buzzing and forager communication, using laser vibrometry. As expected, the flight vibrations met all tested assumptions for resonant oscillations: slow build-up and decay of amplitude; increased frequency following reduction of the inertial load; and decreased frequency following an increase of the mass of the oscillating system. Resonances, however, do not play a significant role in the generation of non-flight vibrations. The strong decrease in main frequency at the end of the pulses indicates that these were driven at a frequency higher than the natural frequency of the system. Despite significant differences regarding the main frequency components and their oscillation amplitudes, the mechanism of generation is apparently similar in annoyance buzzing and forager vibrations. Both types of non-flight vibration induced oscillations of the wings and the legs in a similar way. Since these body parts transform thoracic oscillations into airborne sounds and substrate vibrations, annoyance buzzing can also be used to study mechanisms of signal generation and transmission potentially relevant in forager communication under controlled conditions.

The sound field generated by tethered stingless bees (Melipona scutellaris): inferences on its potential as a recruitment mechanism inside the hive.

In stingless bees, recruitment of hive bees to food sources involves thoracic vibrations by foragers during trophallaxis. The temporal pattern of these vibrations correlates with the sugar concentration of the collected food. One possible pathway for transferring such information to nestmates is through airborne sound. In the present study, we investigated the transformation of thoracic vibrations into air particle velocity, sound pressure, and jet airflows in the stingless bee Melipona scutellaris. Whereas particle velocity and sound pressure were found all around and above vibrating individuals, there was no evidence for a jet airflow as with honey bees. The largest particle velocities were measured 5 mm above the wings (16.0+/-4.8 mm s(-1)). Around a vibrating individual, we found maximum particle velocities of 8.6+/-3.0 mm s(-1) (horizontal particle velocity) in front of the bee's head and of 6.0+/-2.1 mm s(-1) (vertical particle velocity) behind its wings. Wing oscillations, which are mainly responsible for air particle movements in honey bees, significantly contributed to vertically oriented particle oscillations only close to the abdomen in M. scutellaris (distances < or =5 mm). Almost 80% of the hive bees attending trophallactic food transfers stayed within a range of 5 mm from the vibrating foragers. It remains to be shown, however, whether air particle velocity alone is strong enough to be detected by Johnston's organ of the bee antenna. Taking the physiological properties of the honey bee's Johnston's organ as the reference, M. scutellaris hive bees are able to detect the forager vibrations through particle movements at distances of up to 2 cm.

Non-ovipositing nurse workers with developed ovaries in trigona cilipes cilipes (Hymenoptera, Meliponini)

Numerous species of tropical stingless bees (Hymenoptera, Meliponini) have workers that lay eggs even inthe presence of a queen, i.e., queenright colonies. These worker eggs, which are laid during cell provisioningand oviposition process (POP), are eaten mainly by the queen. In this work, we studied POP in a colonyof Trigona cilipes in the queenright and queenless stages. POP behavior was observed on 67 occasions. Inaddition, the ovaries of different aged workers in both stages were analyzed. Although workers in both stagesof the colony possessed developed ovaries, they never oviposited, despite showing behavior similar to thatseen in species with workers which lay eggs. This form of sterility is outstanding among social insects andis comparable only to other meliponines that have fully sterile workers.

A stingless bee (Melipona seminigra) marks food sources with a pheromone from its claw retractor tendons.

By depositing scent marks on flowers, bees reduce both the search time and the time spent with the handling of nonrewarding flowers. They thereby improve the efficiency of foraging. Whereas in honey bees the source of these scent marks is unknown, it is assumed to be the tarsal glands in bumble bees. According to histological studies, however, the tarsal glands lack any openings to the outside. Foragers of the stingless bee Melipona seminigra have previously been shown to deposit an attractant pheromone at sugar solution feeders, which is secreted at the tips of their tarsi. Here we show that the claw retractor tendons have specialized glandular epithelia within the femur and tibia of all legs that produce this pheromone. The secretion accumulates within the hollow tendon, which also serves as the duct to the outside, and is released from an opening at the base of the unguitractor plate. In choice experiments, M. seminigra was attracted by feeders baited with pentane extracts of the claw retractor tendons in the same way as it was attracted by feeders previously scent marked by foragers. Our results resolve the seeming contradiction between the importance of foot print secretions and the lack of openings of the tarsal glands.

Shape differences rather than size differences between castes in the Neotropical swarm-founding wasp Metapolybia docilis (Hymenoptera: Vespidae, Epiponini).

BACKGROUND: Swarm-founding epiponine wasps are an intriguing group of social insects in which colonies are polygynic (several queens share reproduction) and differentiation between castes is often not obvious. However, caste differences in some may be more pronounced in later phases of the colony cycle. RESULTS: Using morphometric analyses and multivariate statistics, it was found that caste differences in Metapolybia docilis are slight but more distinct in latter stages of the colony cycle. CONCLUSIONS: Because differences in body parts are so slight, it is proposed that such variation may be due to differential growth rates of body parts rather than to queens being larger in size, similar to other previously observed epiponines.