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SIGNIFICANCE: • The laying workers of the Cape honey bee continue to negatively affect the South African beekeeping industry, with more losses suffered in the northern regions of the country • The reproductive parasites enter susceptible host colonies, activate their ovaries, and lay diploid eggs, leading to colony dwindling and collapse. • Diploidy in eggs produced by unmated laying workers arises from thelytokous parthenogenesis, first discovered in honey bees by a hobbyist beekeeper. • We examine the consequences of thelytokous parthenogenesis and outline what is being done to understand and limit the spread of the laying workers of the Cape honey bee.

Kairomones are chemical signals that mediate interspecific interactions beneficial to organisms that detect the cues. These attractants can be individual compounds or mixtures of herbivore-induced plant volatiles (HIPVs) or herbivore chemicals such as pheromones, i.e., chemicals mediating intraspecific communication between herbivores. Natural enemies eavesdrop on kairomones during their foraging behaviour, i.e., location of oviposition sites and feeding resources in nature. Kairomone mixtures are likely to elicit stronger olfactory responses in natural enemies than single kairomones. Kairomone-based lures are used to enhance biological control strategies via the attraction and retention of natural enemies to reduce insect pest populations and crop damage in an environmentally friendly way. In this review, we focus on ways to improve the efficiency of kairomone use in crop fields. First, we highlight kairomone sources in tri-trophic systems and discuss how these attractants are used by natural enemies searching for hosts or prey. Then we summarise examples of field application of kairomones (pheromones vs. HIPVs) in recruiting natural enemies. We highlight the need for future field studies to focus on the application of kairomone blends rather than single kairomones which currently dominate the literature on field attractants for natural enemies. We further discuss ways for improving kairomone use through attract and reward technique, olfactory associative learning, and optimisation of kairomone lure formulations. Finally, we discuss why the effectiveness of kairomone use for enhancing biological control strategies should move from demonstration of increase in the number of attracted natural enemies, to reducing pest populations and crop damage below economic threshold levels and increasing crop yield.

BACKGROUND: Biological control plays a key role in reducing crop damage by Tuta absoluta (Meyrick) and Trialeurodes vaporariorum (Westwood), which cause huge yield losses in tomato (Solanum lycopersicum L.). The mirid predator Nesidiocoris tenuis (Reuter) preys heavily on these pests, with satisfying control levels in tomato greenhouses. Although N. tenuis is known to be attracted to volatiles of tomato plants infested by T. absoluta and whitefly, little is known about the specific attractive compounds and the effect of prey density on the predator response. RESULTS: Y-tube olfactometer bioassays revealed that the attraction of N. tenuis to tomato volatiles was positively correlated with the density of T. absoluta infestation, unlike T. vaporariorum infestation. The predator was also attracted to volatiles of T. absoluta larval frass, but not to T. vaporariorum honeydew or T. absoluta sex pheromone. Among the herbivore-induced plant volatiles (HIPVs) that characterised the attractive plants infested with 20 T. absoluta larvae, olfactometer bioassays revealed that N. tenuis is attracted to the monoterpenes α-pinene, α-phellandrene, 3-carene, β-phellandrene and β-ocimene, whereas (E)-β-caryophyllene was found to repel the predator. In dose–response bioassays, the five-component blend of the attractants elicited a relatively low attraction in the predator, and removal of β-phellandrene from the blend enhanced the attraction of the predator to the resulting four-component blend, suggesting synergism among four monoterpenes. CONCLUSION : These findings suggest that a four-component blend of α-pinene, α-phellandrene, 3-carene and β-ocimene could be used as a kairomone-based lure to recruit the predator for the biological control of T. absoluta and T. vaporariorum.

The antestia bug Antestiopsis thunbergii (Gmelin 1790) is one of most damaging pests of Arabica coffee in eastern and southern Africa. It feeds on coffee vegetative parts and fruits, leading to yield and quality reduction. The present study aims to predict the impact of temperature increase on the distribution and abundance of A. thunbergii over an elevation gradient, ranging from 1000 to 1700 m asl, located on Mt. Kilimanjaro, Tanzania. Temperature-dependent phenology models were developed using a complete life table study at 7 constant temperatures. Three indices assessing infestation risk were computed and mapped over the elevation gradient using the phenology models and temperature data for year 2013 and predictions for 2055 (AFRICLIM database): 1) the establishment risk index (ERI), which characterizes the suitability of a geographical area for the insect establishment, 2) the generation index (GI), which estimates the mean number of generations per year, and 3) the activity index (AI), which indicates the population growth rate. Under 2055 temperature predictions, the ERI will decrease by 0.13 at elevations between 1000 and 1100 m asl, and increase by 0.24 between 1500 and 1700 m asl, indicating that high elevations will be more suitable for antestia bug establishment in the future. The number of generations per year will remain constant at elevations between 1000-1100 m asl, but will increase by one generation between 1500-1700 m asl. By 2055, the AI will increase by 1.71 at high elevations leading to higher population growth as a result of temperature rising. These results globally indicate a risk of increasing antestia bug infestation in the highest coffee producing areas of East Africa highlands in the coming decades. These areas are renowned for the high quality of their coffee and mitigation strategies against climate change are therefore needed to minimize the antestia bug risk.

International audience; The retinue behavior of worker bees of Apis cerana cerana and Apis mellifera ligustica in two types of mixed-species colonies were studied to determine whether observed behaviors are pre- or post-speciation developments. In A. cerana queen-led mixed colonies, almost equal numbers of A. cerana workers (53.4 ± 7.4) and A. mellifera workers (51.2 ± 8.1) attended the A. cerana queen; while in A. mellifera queen-led mixed colonies, the A. mellifera queen attracted significantly fewer (47.8 ± 5.9) A. cerana workers than A. mellifera workers (51.9 ± 4.6). Thus about 100 workers in total were attracted to each queen. In pure A. cerana and A. mellifera colonies, the queen attracted 105.8 ± 9.1 and 107.8 ± 11.2 workers, respectively, there being no significant difference between them. Only the pheromones 9-ODA, 9-HDA and 10-HDA of the queens were significantly different and the workers did not show avoidance behavior to either hetero-specific queen. Both species of workers were attracted by the queens and engaged in retinue behavior, suggesting that the retinue response was not related to a specific queen pheromone or colony environment. This non-specific queen retinue behavior in the mixed colonies indicates that the queen pheromones can be transmitted among the workers from the two species without any obstacles. We conclude that retinue behavior itself as well as the pheromones of the queens that induce this behavior are both primitive, conserved traits that preceded speciation in apine bees.

International audience; It was determined that 300 Cape workers, Apis mellifera capensis (collected from each of 6 colonies at each of 5 localities about 200 km apart along an 800 km transect in the Western and Eastern Cape Provinces, South Africa) was the sample size required to statistically estimate the proportions of workers with spermathecae at each location at 95% confidence levels. Because of the extremely clinal nature of this honeybee population, we tested the hypotheses that (1) ovarian number and development of the spermatheca covary in Cape workers, and (2) covary clinally as well. A regression analysis revealed that the frequencies of bees with spermathecae significantly decreased from west to east, with Stellenbosch having the highest and Grahamstown the lowest frequencies. Spermatheca size also significantly decreased from west to east. A multiple regression analysis revealed that the number of ovarioles significantly decreased from west to east and also differed significantly between workers with and without a spermatheca. Moreover, the number of ovarioles was significantly correlated with the size of the spermatheca and workers without it had significantly fewer ovarioles. Both hypotheses are confirmed. The outcomes of these measurements will provide a more quantitative basis for estimates of effective social parasitism among these bees along a geographic continuum.