Randall Hepburn

Behavioural basis for social parasitism of Cape honeybees (Apis mellifera capensis)

Cape honeybee workers show important pre-adaptations for social parasitism and can cause the dwindling colony syndrome of host colonies. Parasitic workers may drift or actively dis- perse into host colonies. They may also join absconding swarms, which can merge with host colonies. After transmission, parasitic workers have to establish themselves in the host, which is probably pro- moted by their spatial distribution, their readiness to gain trophallactic dominance and their ability to survive worker-worker aggression. Established parasitic workers have to evade egg removal by other workers in host colonies. The resulting offspring is preferentially fed, can be expected to be highly virulent and may show different behaviour in the course of infestation. It is unknown why and how the host queen is lost. High numbers of parasitic workers are reared until the host colony dies or absconds. This offspring can infest new host colonies, thereby completing the social parasitic life cycle. Apis mellifera capensis / Apis mellifera scutellata / honeybee / social parasitism / worker repro- duction

Effects of Soil Type, Moisture, and Density on Pupation Success of Aethina tumida (Coleoptera: Nitidulidae)

Abstract We tested the effects of different soils (soils A–F) representing four soil types, two moisture extremes (wet and dry), and two soil densities (packed and tilled) on the number of emerging Aethina tumida Murray (Coleoptera: Nitidulidae) adults. We further determined the effect of soil type and A. tumida sex on the time spent in the soil (where the beetle pupates). Three thousand A. tumida larvae were placed in the moist soil treatments (wet/packed and wet/tilled), of which 2,746 emerged from the soil as adults. Additionally, 3,000 larvae were placed in the dry soil treatments (dry/packed and dry/tilled), of which none emerged as adults. In only one soil were emersion rates different from those in other soils. For every soil, there were significantly more emerging A. tumida in the wet treatments than in the dry ones. Female A. tumida spent less time in the soil than male A. tumida but only by an average of less than half a day. Soil type did affect the length of time A. tumida spent as pupae, despite which average emersion as adults occurred within a tight range. The data suggest that biological requirements of A. tumida may limit/enhance their reproductive potential in various soil environments (especially in dry climates).

Laboratory rearing of small hive beetles Aethina tumida (Coleoptera, Nitidulidae)

The small hive beetle (Aethina tumida, SHB) is a common honey bee (Apis mellifera) parasite in Africa that causes little damage to strong colonies (Lundie, 1940). However, it is a serious threat in the Western Hemisphere where the beetle has been introduced recently (Elzen et al., 1999) and where host colonies lack the behavioural resistance mechanisms of African honey bees (Neumann et al., 2001). Captive breeding of this parasite is an important research technique to produce SHB under controlled conditions for experiments. Here we report on a simple technique for rearing SHB in the laboratory.

Hygienic Behavior of Cape and European Apis mellifera (Hymenoptera: Apidae) toward Aethina tumida (Coleoptera: Nitidulidae) Eggs Oviposited in Sealed Bee Brood

Abstract In this study, we tested for the presence and efficacy of hygienic behavior by Cape honey bees in South Africa and European honey bees, Apis mellifera L. (Hymenoptera: Apidae), of mixed origin in the United States toward Aethina tumida Murray (Coleoptera: Nitidulidae) eggs oviposited in sealed bee brood. We looked for colony differences in removal rates of brood in cells with cappings perforated by A. tumida within each subspecies to identify colonies within location that display superior hygienic behavior. Finally, we determined the oviposition rate (number of A. tumida-perforated cells actually oviposited in by A. tumida/total number of A. tumida-perforated cells) in A. tumida-perforated cells and the number of A. tumida eggs oviposited in each cell. There were no colony differences within subspecies for the removal of normal capped brood, artificially perforated brood (capped cells perforated by experimenter with a pin), and A. tumida-perforated brood. For both subspecies, the bees removed significantly more A. tumida-perforated brood than either normal or artificially perforated brood. A. tumida oviposited significantly more eggs per cell in Cape colonies than in European colonies, but the oviposition rate in A. tumida-perforated cells did not differ between Cape and European colonies. Both subspecies removed a proportion of A. tumida-perforated brood statistically indistinguishable from the proportion of A. tumida-perforated brood containing A. tumida eggs. Thus, both Cape and European A. mellifera preferentially remove the contents of A. tumida-perforated cells in which A. tumida have actually oviposited.

Aggressive and Docile Colony Defence Patterns in Apis mellifera. A Retreater-Releaser Concept

Colony defence in Apis mellifera involves a variety of traits ranging from ‘aggressive’ (e.g. entrance guarding, recruitment of flying guards) to ‘docile’ (e.g. retreating into the nest) expression. We tested 11 colonies of three subspecies (capensis, scutellata, carnica) regarding their defensiveness. Each colony was selected as reportedly ‘aggressive’, ‘intermediate’ or ‘docile’ and consisted of about 10,000 bees. We applied three stimulation regimes (mechanical disturbance, exposure to alarm pheromones, and the combination of both) and measured their behaviours by tracking the rates of outflying bees at the entrance sites of the test hives. We provided evidence that for mechanical disturbances the test colonies resolved into two response types, if the ‘immediate’ defence response, assessed in the first minute of stimulation, was taken as a function of foraging: ‘releaser’ colonies allocated flying guards, ‘retreater’ colonies reduced the outside-hive activities. This division was observed irrespective of the subspecies membership and maintained in even roughly changing environmental conditions. However, if pheromone and mechanical stimulation were combined, the variety of colony defensiveness restricted to two further types irrespective of the subspecies membership: six of nine colonies degraded their rate of flying defenders with increasing foraging level, three of the colonies extended their ‘aggressiveness’ by increasing the defender rate with the foraging level. Such ‘super-aggressive’ colonies obviously are able to allocate two separate recruitment pools for foragers and flying defenders.

A scientific note on small hive beetle (Aethina tumida) oviposition and behaviour during European (Apis mellifera) honey bee clustering and absconding events

Small hive beetles (Aethina tumida) were discovered in the southeastern USA in 1998 (Eizen et a/., 1999) where they have subsequently caused severe damage to colonies of European-derived subspecies of Apis mel/ifera. However, in their native range of subSaharan Africa (Hepburn & Radloff, 1998), they are considered only minor honey bee pests (Lundie, 1940; Pettis & Shimanuki, 2000); therefore small hive beetle behaviour is little studied and less understood. Here, we report observations on beetle behaviour during European honey bee clustering and absconding events and on beetle oviposition.

Social parasitism of queens and workers in the Cape honeybee (Apis mellifera capensis)

Workers of a queenless honeybee colony can requeen the colony by raising a new queen from a young worker brood laid by the old queen. If this process fails, the colony becomes hopelessly queenless and workers activate their ovaries to lay eggs themselves. Laying Cape honeybee workers (Apis mellifera capensis) produce female offspring as an additional pathway for requeening. We tested the frequency of successful requeening in ten hopelessly queenless colonies. DNA genotyping revealed that only 8% of all queens reared in hopelessly queenless colonies were the offspring of native laying worker offspring. The vast majority of queens resulted from parasitic takeovers by foreign queens (27%) and invading parasitic workers (19%). This shows that hopelessly queenless colonies typically die due to parasitic takeovers and that the parasitic laying workers are an important life history strategy more frequently used than in providing a native queen to rescue the colony. Parasitism by foreign queens, which might enter colonies alone or accompanied by only a small worker force is much more frequent than previously considered and constitutes an additional life history strategy in Cape honeybees.

Nestmate recognition for eggs in the honeybee (Apis mellifera L.)

Colony integrity is fundamental to social insects and is threatened by the reproduction of non-nestmates. Therefore, discrimination between eggs derived from nestmates and non-nestmates would constitute an adaptation to prevent exploitation of the entire cooperative group by unrelated individuals. The removal of nestmate and non-nestmate queen and worker-laid eggs was evaluated in honeybees using colonies of Apis mellifera capensis to test female and of A. m. scutellata to test male eggs. The data show that honeybees can distinguish between nestmate and non-nestmate eggs of both sexes. Moreover, non-nestmate female queen-laid eggs were removed significantly faster than nestmate female worker-laid eggs in A. m. capensis, indicating that nestmate recognition cues can override caste-specific ones. While the experimental manipulation accounts for 37.2% (A. m. scutellata) or 1.6% (A. m. capensis) of variance in relation to egg removal, nestmate recognition explains 33.3% for male eggs (A. m. scutellata) and 60.6% for female eggs (A. m. capensis), which is almost twice as high as the impact of caste (16.7% A. m. scutellata; 25% A. m. capensis). Our data show a stronger effect of nestmate recognition on egg removal in the honeybee, suggesting that cues other than caste-specific ones (viability/kin) can dominate egg removal behavior. In light of intraspecific social parasitism, preventing the reproduction of unrelated individuals (group selection) rather than preferring queens’ eggs (kin selection) appears to be the driving force behind the evolution of egg removal behavior in honeybees.

Geographic variation in the Japanese islands of Apis cerana japonica and in A. cerana populations bordering its geographic range

Genetic variation among Apis cerana japonica isolates from Japan and Apis cerana isolates from the neighboring areas of Russia, South Korea, and Taiwan was determined from DNA sequences of the mitochondrial DNA non-coding region (between tRNA leu and COII). Three haplotypes were identified among 470 colonies samples at 47 Japanese sites. All isolates from the main Japanese Islands of Honshu, Shikoku, and Kyushu belonged to a single haplotype, a previously reported Japan 1 haplotype. Two new haplotypes were found on the far southern Japanese islands of Amami-Oshima and Tsushima (the Japan 3 and Japan 4 haplotypes, respectively). The A. cerana from Russia and South Korea were the Japan 1 isolate, the A. cerana from Taiwan was the previously known Taiwan haplotype. Our studies showed little genetic variation in the mtDNA of A. cerana japonica, indicating that this genomic region is of limited use for detecting genetic variation among closely related populations of A. cerana.ZusammenfassungDie genetische Variation von A. cerana japonica in Japan und A. cerana in den benachbarten Arealen wurde anhand von mitochondrialen DNA Sequenzdaten einer nichtkodierenden Region untersucht. Aus 470 A. cerana japonica Völkern von 47 Standorten in Japan und von 5 A. cerana Völkern einzelner Orte in Russland, Südkorea und Taiwan wurden im Jahr 1997 und 2002 Proben von adulten Arbeiterinnen entnommen. Bei den japanischen Populationen wurden 3 Haplotypen identifiziert, der bereits vorher bekannte Japan 1 Haplotyp und zwei neue Haplotypen (Japan 3 und Japan 4). Der Japan 1 Haplotyp wurde an 43 Lokalitäten auf Honshu, Shikoku und den Kyushu Inseln gefunden, während die Japan 3 und 4 Haplotypen auf den Inseln Amami-Oshima beziehungsweise Tsushima gefunden wurden. Der neue Japan 3 Haplotyp enthielt eine Basensubstitution (T → A) an der einundzwanzigsten Position, der Japan 4 Haplotyp eine an der dreizehnten Position (G → A). Die Ergebnisse zeigten, dass A. cerana japonica eine sehr geringe genetische Variation in der nichtkodierenden Region der mtDNA aufweist

Efficacy of modified hive entrances and a bottom screen device for controlling Aethina tumida (Coleoptera: Nitidulidae) infestations in Apis mellifera (Hymenoptera: Apidae) colonies.

This study was designed to test whether hive entrances reduced with polyvinyl chloride pipe reduce the ingress of Aethina tumida Murray into Apis mellifera L. colonies and whether screen-mesh bottom boards alleviate side effects associated with restricted entrances. Forty-eight colonies distributed equally between two locations each received one of six experimental treatments: 1) conventional solid bottom board and open entrance, 2) ventilated bottom board and open entrance, 3) conventional bottom and 1.9-cm-i.d. pipe entrance, 4) conventional bottom and 3.8-cm pipe entrance, 5) screen bottom and 1.9-cm pipe entrance, and 6) screen bottom and 3.8-cm pipe entrance. Results were inconsistent between apiaries. In apiary 1, colonies with 3.8-cm pipe entrances had fewer A. tuzmida than colonies with open entrances, but this benefit was not apparent in apiary 2. Pipe entrances tended to reduce colony and brood production in both apiaries, and these losses were only partly mitigated with the addition of screened bottom boards. Pipe entrances had no measurable liability concerning colony thermoregulation. There were significantly fewer frames of adult A. mellifera in colonies with 3.8- or 1.9-cm pipe entrances compared with open entrances but more in colonies with screens. There were more frames of pollen in colonies with open or 3.8-cm pipe entrances than 1.9-cm entrances. We conclude that the efficacy of reduced hive entrances in reducing ingress of A. tumida remains uncertain due to observed differences between apiaries. Furthermore, there were side effects associated with restricted entrances that could be only partly mitigated with screened bottom boards.