The least understood aspects of the nutritional needs of bees are the elemental composition of pollen and the bees’ need for a stoichiometrically balanced diet containing the required proportions of nutrients. Reduced plant diversity has been proposed as an indirect factor responsible for the pollinator crisis. We suggest stoichiometric mismatch resulting from a nutritionally unbalanced diet as a potential direct factor. The concentrations and stoichiometric ratios of C, N, S, P, K, Na, Ca, Mg, Fe, Zn, Mn, and Cu were studied in the bodies of honeybees of various castes and sexes and in the nectar and pollen of various plant species. A literature review of the elemental composition of pollen was performed. We identified possible co-limitations of bee growth and development resulting mainly from the scarcity of Na, S, Cu, P and K, and possibly Zn and N, in pollen. Particular castes and sexes face specific limitations. Concentrations of potentially limiting elements in pollen revealed high taxonomic diversity. High floral diversity may be necessary to maintain populations of pollen eaters. Single-species crop plantations, even if these species are rich in nectar and pollen, might limit bee growth and development, not allowing for gathering nutrients in adequate proportions. However, particular plant species may play greater roles than others in balancing honeybee diets. Therefore, we suggest specific plant species that may (1) ensure optimal growth and production of individuals by producing pollen that is exceptionally well balanced stoichiometrically (e.g., clover) or (2) prevent growth and development of honeybees by producing pollen that is extremely unbalanced for bees (e.g., sunflower). Since pollen is generally poor in Na, this element must be supplemented using “dirty water”. Nectar cannot supplement the diet with limiting elements. Stoichiometric mismatch should be considered in intervention strategies aimed at improving the nutritional base for bees.

According to kin selection theory, the colony kin structure of eusocial insects motivates workers' altruistic behaviors and therefore their sterility or restricted reproduction [1]. Indeed, theory and cross-species comparison confirm that workers engage in their own reproduction depending on relatedness among colony members [2, 3]. We show that in a honeybee colony, the workers switch from their typical altruistic role to a more selfish one if at their larval stage there are environmental cues of an upcoming decline in intracolony relatedness. This happens inevitably when a colony multiplies by swarming and replaces the mother queen with her daughter, because the mother queen's workers are faced with rearing the sister queen's offspring related to them half as much as between sisters. Workers developing from the mother queen's eggs immediately after swarming, in a temporarily queenless colony, had more ovarioles in their ovaries and less-developed hypopharyngeal glands producing brood food than control workers reared in queenright conditions. These "rebel" workers were more engaged in laying their own male-determined eggs than in rearing offspring, whether or not the sister queen was present in the colony. The finding of this previously unknown rebel strategy confirms that kin selection shapes both cooperation and conflict in honeybee societies.

The spread of invasive alien plants has considerable environmental and economic consequences, and is one of the most challenging ecological problems. The spread of invasive alien plant species depends largely on long-distance dispersal, which is typically linked with human activity. The increasing domination of the internet will have impacts upon almost all components of our lives, including potential consequences for the spread of invasive species. To determine whether the rise of Internet commerce has any consequences for the spread of invasive alien plant species, we studied the sale of thirteen of some of the most harmful Europe invasive alien plant species sold as decorative plants from twenty-eight large, well known gardening shops in Poland that sold both via the Internet and through traditional customer sales. We also analyzed temporal changes in the number of invasive plants sold in the largest Polish internet auction portal. When sold through the Internet invasive alien plant species were transported considerably longer distances than for traditional sales. For internet sales, seeds of invasive alien plant species were transported further than were live plants saplings; this was not the case for traditional sales. Also, with e-commerce the shape of distance distribution were flattened with low skewness comparing with traditional sale where the distributions were peaked and right-skewed. Thus, e-commerce created novel modes of long-distance dispersal, while traditional sale resembled more natural dispersal modes. Moreover, analysis of sale in the biggest Polish internet auction portal showed that the number of alien specimens sold via the internet has increased markedly over recent years. Therefore internet commerce is likely to increase the rate at which ecological communities become homogenized and increase spread of invasive species by increasing the rate of long distance dispersal.

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Evolution has created different castes of females in eusocial haplodiploids. The difference between them lies in their functions and vulnerability but above all in their reproductive potentials. Honeybee queens are highly fertile. On the other hand, the workers are facultatively sterile. However, rebel workers, i.e. workers that develop in a queenless colony, reproduce more often than normal workers. As a result, the fat body of these bees, which apart from acting as the energy reserve, is also the site of numerous metabolic processes, had to specialize in different functions perfected over millions of years of eusocial evolution. Assuming that the variety of functions manifests itself in the pleomorphic structure of the fat body cells, we predicted that also different parts of the fat body, e.g. from different segments of the abdomen, contain different sets of cells. Such differences could be expected between queens, rebels and normal workers, i.e. females with dramatically different reproductive potentials. We confirmed all these expectations. Although all bees had the same types of cells, their proportion and segmental character corresponded with the caste reproductive potential and physiological characteristics shaped in the evolutionary process. The females with an increased reproductive potential were characterized by the presence of oenocytes in the third tergite and high concentrations of compounds responsible for energy reserves, like glucose, glycogen and triglycerides. Queens had very large trophocytes, especially in the third tergite. Only in workers did we observe intercellular spaces in all the segments of the fat body, as well as high protein concentrations—especially in the sternite. As expected, the rebels combined many features of the queens and normal workers, what with other findings can help understand the ways that led to the origin of different castes in females of eusocial Hymenoptera.

Various animal models are used in the study of alcoholism, with the honeybee (Apis mellifera L.) among them. Here, we tested the hypothesis that foragers show higher intoxication resistance to alcohol than nurses, an issue thus far not investigated. To this end, we measured the latency to full sedation when exposed to alcohol in foragers, nurses and reverted nurses. In addition, we measured alcohol dehydrogenase (ADH) levels in these worker castes. Caste status was confirmed by comparison of the size of their hypopharyngeal glands. We detected high intoxication resistance to alcohol and presence of ADH in foragers. In nurses, we detected significantly lower intoxication resistance to alcohol and no ADH. These between-caste differences cannot be explained by the age difference between castes as in reverted nurses, characterized by similar age to foragers, we detected an intermediate intoxication resistance to alcohol and no ADH. Our results suggest possible natural exposure to alcohol in different castes of workers. As such, we further develop the honeybee as a model in alcoholism-related research and open new research avenues.

In the honeybee, diploid larvae fed with royal jelly develop into reproductive queens, whereas larvae fed with royal jelly for three days only and subsequently with honey and pollen develop into facultatively sterile workers. A recent study showed that worker larvae fed in a queenless colony develop into another female polyphenic form: rebel workers. These rebel workers are more queenlike and have greater reproductive potential than normal workers. However, it was unclear whether larvae orphaned at any time during their feeding period can develop into rebels. To answer this question, the anatomical features of newly emerged workers reared in queenless conditions at different ages during the larval period were evaluated. Our results showed that larvae orphaned during the final four or more days of their feeding life develop into rebel workers with more ovarioles in their ovaries, smaller hypopharyngeal glands, and larger mandibular and Dufour’s glands compared with typical workers with low reproductive potential that were reared with a queen or orphaned at the third to last or a later day of feeding life.

Certain ants perform rescue behaviour for other ants that require help, and the expression of rescue behaviour is hypothesized to depend on signals (“calls for help”) sent by the imperilled individuals. We studied whether the mandibular glands were involved in the elicitation of rescue behaviour in Formica cinerea Mayr ants. In the first experiment, we determined the occurrence and characteristics of rescue behaviour directed towards nest mates with impaired mandibular gland communication. We did not observe any difference in rescue behaviour directed towards individuals who were untreated, treated with paint over the mandibles, or sham-treated with paint over the thorax. In the second experiment, we determined whether rescue behaviour would occur towards dummy ants coated with the contents of the mandibular glands. Compared with the control untreated nest mates, we found that rescue behaviour was not directed towards either the untreated dummy ants or the dummy ants covered with crushed mandibular glands. Our results indicated that the “call for help” signal does not originate from the mandibular glands. Therefore, we propose that gaster-tip glands represent a plausible alternative source of rescue-eliciting pheromone(s) for the F. cinerea ants examined in this study.Electronic supplementary materialThe online version of this article (doi:10.1007/s00040-017-0547-x) contains supplementary material, which is available to authorized users.