The origin and evolution of pollen transport in bees (Hymenoptera: Anthophila)

The ability to transport pollen from flowers back to the nest represents a key innovation in the evolution of bees from predatory wasp ancestors. Currently, the origin and evolution of pollen transport remains unsettled. Older hypotheses proposed that crop transport was the original mode of pollen transport, but more recent molecular phylogenies have cast doubt on that view. Instead, more recent hypotheses contend that external transport of dry pollen is ancestral in bees. Here, I propose a new hypothesis to explain the origin and subsequent evolution of pollen transport in bees. I propose that pollen transport arose from adult pollen-feeding behavior and that internal transport of pollen is ancestral in bees. This then led to the evolution of external moist transport, which first required a transition step whereby pollen is temporarily accumulated on the venter on a patch of specialized hairs. Finally, external glazed and dry transport evolved from external moist pollen transport, and the evolution of dry transport led to changes in the location of scopae from the original location on the hind tibia and basitarsus. I illustrate many of these hypothetical evolutionary steps using modern-day bee behavior as an example, with a particular focus on the bee Perdita tortifoliae. Examination of the evolution of pollen transport of pollen wasps (subfamily Masarinae) reveals that they have undergone a parallel evolutionary change. Overall, I lay out a broad hypothetical framework to explain the origin and subsequent evolution of pollen transport in bees. This marks a return to the earlier hypothesis that crop transport is ancestral, and it also represents the first in-depth hypothesis to explain how external transport of moistened pollen could have evolved. The evolutionary history of bees has many implications for the biology of bees in the present day, and I lay out a number of predictions that could help confirm or refute my hypotheses.

Red and black mason wasp, Pachodynerus erynnis (Lepeletier)

Pachodynerus erynnis (Lepeletier) is a predatory wasp that specializes in preying upon caterpillars, the larvae of moths and butterflies (Lepidoptera). This insect does not yet have an officially accepted common name and has been referred to as the red and black mason wasp, red-marked Pachodynerus, and a mason wasp. As with other closely related wasps, Pachodynerus erynnis does not form a communal hive, but builds solitary nests in holes or crevices of trees or man-made structures, as well as abandoned nests created by other cavity-nesting bees and wasps. The red and black mason wasp frequently visits flowering plants and can be found entering nesting cavities nearby. This insect is considered highly beneficial because it feeds on several key caterpillar pests, including armyworms (Spodoptera spp.), cutworms (Agrotis spp.), and loopers (Noctuoidea), and has been associated with increased pest control in managed landscapes. Although fairly common, this wasp often goes unnoticed due to its solitary nature and quick flight. Also published on the Featured Creatures website at http://entnemdept.ufl.edu/creatures/MISC/WASPS/Pachodynerus_erynnis.html

A bilateral gynandromorph of Discoelius dufourii (Hymenoptera, Vespidae, Zethinae): morphology and mating behaviour

A gynandromorph is an organism combining both female- and male-type tissues. While the vast majority of studies have described the morphology of gynandromorphs, their sexual behaviours remain under-explored. We studied a predominantly bilateral gynandromorph specimen of the predatory wasp Discoelius dufourii (Hymenoptera: Vespidae: Zethinae) reared from a trap-nest. In addition to describing the morphology, we explored the gynandromorph’s response to a conspecific female, comparing it with the behavioural interactions between normal males and females of D. dufourii and the phylogenetically related D. zonalis. For most specific behavioural elements, males of both Discoelius species exhibited a greater frequency and a higher probability of occurrences of the behaviour than did females. However, aggression and plopping behaviours were prevalent in females. The gynandromorphic specimen demonstrated behavioural activities similar to those of a male, including a relatively frequent mate body antennation and an attempt to mount a female. However, it approached the female less frequently in comparison to conspecific normal males, and it did not demonstrate substrate antennation and jumping, typical of Discoelius male mating behaviour. Based on the parameters of the nest cell, the probability of the development of the gynandromorphic specimen from an unfertilized (male) egg was higher than the probability of development from a fertilized (female) egg.

Escape-hatching responses of individual treefrog embryos vary with threat level in wasp attacks: a mechanistic analysis

Theory predicts that prey behavioural responses should reflect the level of risk posed by predators. We investigated how red-eyed treefrog embryos perceive and respond to spatially variable risk during wasp attacks on their clutches. First, we spatially restricted wasp activity on clutches and compared hatching of wasp-exposed, adjacent, and protected embryos. Hatching occurred in all zones but increased with exposure, being highest in directly exposed embryos. Second, we videotaped wasps attacking clutches and compared the experiences of embryos that hatched first and those that did not hatch until later. Embryos that hatched first experienced more predatory wasp activity directed at themselves or at siblings within a 2-egg radius. Models predicting hatching indicate that cues used to assess risk originate from the behaviour of wasps, rather than other embryos. This research demonstrates that embryos can integrate information about predator behaviour and proximity to respond appropriately based on their level of risk.