Nesting Biology and Social Behavior of Xenochlora Bees (Hymenoptera: Halictidae: Augochlorini) from Perú

Abstract

The augochlorine (Halictidae) bee genus Xenochlora is the diurnal sister group to the nocturnal Megalopta, both of which are stem-nesting halictid bees. Here we present notes on the nesting biology and social behavior in four nests of Xenochlora nigrofemorata and one nest of X. ianthina from Madre de Dios, Peru. All nests contained multiple females and dissections of X. nigrofemorata indicated within nest reproductive differentiation among females that is associated with body size. Size variation among females is conspicuous and a variety of morphometrics are examined to document it. A genal index is used to describe cephalic variation, and results are compared with seven other halictine bees. All morphometrics were investigated for measurement error. Nests of Xenochlora appear to be founded by single females and multifemale nests clearly exhibit parasocial behavior and we hypothesize that they temporally switch between semisocial, eusocial and possibly communal phases.KEYWORDS: Halictidae, Augochlorini, Xenochlora, social evolution, size variation, stem nest RESUMEN: El genero de abejas Xenochlora (Augochlorini, Halictidae) es el grupo hermano diurno del genero nocturno Megalopta. Ambos grupos son abejas que construyen sus nidos en madera en descomposicion. Aqui presentamos anotaciones sobre la biologia de anidacion y comportamiento social en cuatro nidos de Xenochlora nigrofemorata y un nido de X. ianthina en Madre de Dios, Peru. Todos los nidos contenian multiples hembras y las disecciones de X. nigrofemorata indican que hay diferenciacion reproductiva entre las hembras de un nido, asociada con el tamaho del cuerpo. El polimorfismo entre las hembras es evidente y una serie de mediciones morfometricas son examinadas para documentar la variation en tamaho. Un indice genal es utilizado para describir el polimorfismo cefalico y los resultados son comparados con otras especies de abejas halictidas. Todas las mediciones morfometricas fueron analizadas para determinar el error de medicion. Los nidos de Xenochlora parecen ser fundados por hembras solitarias y los nidos con hembras multiples exhiben claramente un comportamiento parasocial y es posible que temporalmente intercambien entre fases semisocial, eusocial y posiblemente comunal.

Biology of a nocturnal bee,Megalopta atra(Hymenoptera: Halictidae; Augochlorini), from the Panamanian highlands

“…There is considerable intraspecific variation in female body size (range of intertegular width=2.56-3.76mm), including enlarged processes of the head and genal spines, as known for some other Neotropical, social augochlorine bees (reviewed in Sakagami and Moure 1965;Tierney et al 2008), and large body size is thought to be associated with social dominance (Arneson and Wcislo 2003;Smith et al 2008). An ovarian index was measured (sum of three largest oocytes/ intertegular width) to account for the scaling effects of body size on ovary size.…”

“…Yanega (1989) and suggest that the actual length of the brood rearing season, and so greater variations in temperature, may be more important in defining this variation in size within a population. However, this reasoning cannot account for the highly variable cephalic and body sizes found among Neotropical augochlorines, where seasonal temperatures are less variable and polymorphisms are more extreme (Sakagami and Moure 1965;Tierney et al 2008). For Megalopta, body size appears to be an important factor determining social reproductive status (Arneson and Wcislo 2003), although whether size differences are environmentally determined by floral availability, or by the reduction of pollen provisions by brood cell parasites (Smith et al 2008), requires additional data and broader assessment.…”

“…Ovarian development was measured as the sum length of the three largest terminal oocytes and mating status was identified by the presence or absence of sperm in the spermatheca. Body size was determined by intertegular distance, following Tierney et al (2008). The number of nicks and tears along the distal margin of this wing was taken as a measure of wing wear.…”

Photic niche invasions: phylogenetic history of the dim-light foraging augochlorine bees (Halictidae)

“…coloration and ocellar size), but otherwise appears to resemble Megalopta in form, social behaviour and nesting biology [25]. Owing to a lack of ethological data, we cannot rule out facultative crepuscular activity, but we do know they are diurnal foragers (D. W. ).…”

“…(a) Specimen collection and study taxa Bees were collected at light traps or from nests (see [23][24][25][26]) at localities given in the electronic supplementary material, table S1. The most abundant genus is Megalopta (approx.…”