A key to the subgenera of the orchid bee genus Euglossa (Hymenoptera: Apidae)

The infrageneric classification of the orchid bee genus Euglossa Latreille (Apinae: Euglossini) has historically comprised six or seven subgenera and a plethora of species groups, many of which are demonstrably monophyletic. Nonetheless, challenges remain, particularly in relation to the subgenus Glossurella Dressler. Herein a new key to subgenera is presented and four problematic species groups of Glossurella are removed to separate subgeneric entities: Eurhytisma subgen. n., Glossurodes subgen. n., Parisoglossa subgen. n., and Trachyglossa subgen. n.

Nests of Eufriesea aff. auriceps (Hymenoptera, Apidae, Euglossini) in remnants of Atlantic Forest and reforested areas

In recent decades, the use of the trap-nest technique has helped to increase knowledge on the nest architecture of many orchid bee species. This study describes the nest architecture of Eufriesea aff. auriceps constructed in trap-nests made of dried bamboo internodes (canes). The nests were placed in remnants of Atlantic forest and in reforested areas next to forest remnants and monitored monthly from August 2015 to August 2016 and from August 2018 to August 2019 in southern Brazil. The bamboo internodes occupied by bees varied in internal diameter from 1.0cm to 2.0 cm (`X = 1.7; SD = 0.3; N = 12) and in length from 11.0 cm to 28.0 cm (`X = 19.5; SD = 4.8; N = 12). The total size of the nests inside the bamboo internodes ranged from 9.0 cm to 19.9 cm (`X = 14.3; SD= 3.9; N = 12). The number of brood cells constructed per nest varied from 1 to 10 (`X = 4.0; SD = 2.3; N = 15). The cells were built with small pieces of bark cemented with resin, linearly arranged along the bamboo tube. Internally, the cell wall was lined with resin. The cells measured 1.5-3.0 cm (`X = 2.3 ± 0.5; N = 48) in length and 1.4-1.7 (`X = 1.5 ± 0.1; N = 17) cm in width. The internal contour of the cells was elliptical. Females of Eufriesea aff. auriceps occupied trap-nests in both the forest remnants and in areas undergoing restoration.

First Case of Gynandromorphism in the Orchid-Bee Eulaema meriana (Olivier) (Hymenoptera: Apidae)

The discovery of the first case of gynandromorphism in Eulaema meriana (Olivier) is described and illustrated. A specimen from Los Ríos, western Ecuador, discovered in the Instituto Nacional de Biodiversidad (MECN) collection, exhibits mostly male features on the left and female features on the right, except for the jugal comb of the hind wing and terminalia. This finding is compared to other reported cases in orchid bees.

Transcriptomic signatures of ageing vary in solitary and social forms of an orchid bee

Eusocial insect queens are remarkable in their ability to maximise both fecundity and longevity, thus escaping the typical trade-off between these two traits. Several mechanisms have been proposed to underlie the remoulding of the trade-off, such as reshaping of the juvenile hormone pathway, or caste-specific susceptibility to oxidative stress. However, it remains a challenge to disentangle the molecular mechanisms underlying the remoulding of the trade-off in eusocial insects from caste-specific physiological attributes that have subsequently arisen. The socially polymorphic orchid bee Euglossa viridissima represents an excellent model to address the role of sociality per se in longevity as it allows direct comparisons of solitary and social individuals within a common genetic background. We investigated gene expression and juvenile hormone levels in young and old bees from both solitary and social nests. We found 902 genes to be differentially expressed with age in solitary females, including genes involved in oxidative stress, versus only 100 genes in social dominant females, and 13 genes in subordinate females. A weighted gene co-expression network analysis further highlights pathways related to ageing in this species, including the TOR pathway. Eleven genes involved in translation, apoptosis and DNA repair show concurrent age-related expression changes in solitary but not in social females, representing potential differences based on social status. Juvenile hormone titres did not vary with age or social status. Our results represent an important step in understanding the proximate mechanisms underlying the remodelling of the fecundity/longevity trade-off that accompanies the evolutionary transition from solitary life to eusociality.

Transcriptomic signatures of ageing vary in solitary and social forms of an orchid bee

Eusocial insect queens are remarkable in their ability to maximise both fecundity and longevity, thus escaping the typical trade-off between these two traits. In species exhibiting complex eusocial behaviour, several mechanisms have been proposed to underlie the remoulding of the trade-off, such as reshaping of the juvenile hormone pathway, or caste-specific susceptibility to oxidative stress. However, it remains a challenge to disentangle the molecular mechanisms underlying the remoulding of the trade-off in eusocial insects from caste-specific physiological attributes that have subsequently arisen due to their different life histories. Socially plastic species such as the orchid bee Euglossa viridissima represent excellent models to address the role of sociality per se in longevity as they allow direct comparisons of solitary and social individuals within a common genetic background. We present data on gene expression and juvenile hormone levels from young and old bees, from both solitary and social nests. We found 940 genes to be differentially expressed with age in solitary females, versus only 14 genes in social dominant females, and seven genes in subordinate females. We performed a weighted gene co-expression network analysis to further highlight candidate genes related to ageing in this species. Primary “ageing gene” candidates were related to protein synthesis, gene expression, immunity and venom production. Remarkably, juvenile hormone titres did not vary with age or social status. These results represent an important step in understanding the proximate mechanisms underlying the remodeling of the fecundity/longevity trade-off that accompanies the evolutionary transition from solitary life to eusociality.Significance statementThe remarkably long lifespan of the queens of eusocial insects despite their high reproductive output suggests that they are not subject to the widespread trade-off between fecundity and longevity that governs solitary animal life histories, yet surprisingly little is known of the molecular mechanisms underpinning their longevity. Using a socially plastic bee in which some individuals of a population are social whilst others are solitary, we identified hundreds of candidate genes and related gene networks that are involved in the remoulding of the fecundity/longevity tradeoff. As well as identifying candidate ageing genes, our data suggest that even in incipient stages of sociality there is a marked reprogramming of ageing; long live the queen.