Influence of honey bee (Apis mellifera) breeding on wing venation in Serbia and neighbouring countries

In order to improve the productivity of honey bees (Apis mellifera), some of their traits are selected by breeding. On one hand, breeding is mainly based on the natural geographical variation of this species; on the other hand, mass production and distribution of artificially selected queens can significantly affect the natural geographic variation of honey bees. In this study, we have compared honey bee wings originating from breeding and non-breeding populations in Serbia. In the comparison, we have also used data from a large area of south-eastern Europe. The wings were measured using the 19 landmarks indicated on the wing images. The coordinates were analysed using the methodology of geometric morphometrics. We found that honey bees obtained from honey bee queen breeder differed in wing venation from surrounding populations, which are under natural selection. Therefore, we argue against including populations under artificial selection in the analysis of the natural geographical variation of honey bees. In our analysis of non-breeding samples, we found that in south-eastern Europe there is continuous variation in wing venation and no clear boundaries between A. m. carnica, A. m. cecropia, and A. m. macedonica.

In Search of Apis mellifera pomonella in Kazakhstan

Apis mellifera pomonella is one of two subspecies that represent the eastern limits of honey bee (Apis mellifera) distribution, and it is important to understand its biogeography and evolution. Despite this, A. m. pomonella was not investigated after its discovery 20 years ago. In particular, it is not known if it was hybridized or not with exotic subspecies introduced by beekeepers. In this study, we analysed the variation in honey bee forewing shape in Kazakhstan. Bees were collected from apiaries, where the origin of the queens was not controlled by beekeepers; they formed a group called "local bees", and apiaries where queens declared as either A. m. carnica or A. m. mellifera were obtained from queen breeders. The two later groups were called "exotic bees". We showed that local bees are still distinct from exotic ones. However, some samples showed signs of introgression with exotic subspecies from lineage C. In terms of wing shape, the local bees were most similar to lineage O. We concluded that the local bees most likely represented A. m. pomonella. We provided wing images and identification data, which can help to identify A. m. pomonella and protect it in the future. It is interesting that the nearby honey bee population sourced from China, which is not separated by any clear barrier to gene flow, belonged to lineage M.

Honey bee (Apis mellifera) wing images: a tool for identification and conservation

BACKGROUND

The honey bee (Apis mellifera) is an ecologically and economically important species that provides pollination services to natural and agricultural systems. The biodiversity of the honey bee in parts of its native range is endangered by migratory beekeeping and commercial breeding. In consequence, some honey bee populations that are well adapted to the local environment are threatened with extinction. A crucial step for the protection of honey bee biodiversity is reliable differentiation between native and nonnative bees. One of the methods that can be used for this is the geometric morphometrics of wings. This method is fast, is low cost, and does not require expensive equipment. Therefore, it can be easily used by both scientists and beekeepers. However, wing geometric morphometrics is challenging due to the lack of reference data that can be reliably used for comparisons between different geographic regions.

FINDINGS

Here, we provide an unprecedented collection of 26,481 honey bee wing images representing 1,725 samples from 13 European countries. The wing images are accompanied by the coordinates of 19 landmarks and the geographic coordinates of the sampling locations. We present an R script that describes the workflow for analyzing the data and identifying an unknown sample. We compared the data with available reference samples for lineage and found general agreement with them.

CONCLUSIONS

The extensive collection of wing images available on the Zenodo website can be used to identify the geographic origin of unknown samples and therefore assist in the monitoring and conservation of honey bee biodiversity in Europe.

Using the Software DeepWings© to Classify Honey Bees across Europe through Wing Geometric Morphometrics

DeepWings© is a software that uses machine learning to automatically classify honey bee subspecies by wing geometric morphometrics. Here, we tested the five subspecies classifier (A. m. carnica, Apis mellifera caucasia, A. m. iberiensis, Apis mellifera ligustica, and A. m. mellifera) of DeepWings© on 14,816 wing images with variable quality and acquired by different beekeepers and researchers. These images represented 2601 colonies from the native ranges of the M-lineage A. m. iberiensis and A. m. mellifera, and the C-lineage A. m. carnica. In the A. m. iberiensis range, 92.6% of the colonies matched this subspecies, with a high median probability (0.919). In the Azores, where the Iberian subspecies was historically introduced, a lower proportion (85.7%) and probability (0.842) were observed. In the A. m mellifera range, only 41.1 % of the colonies matched this subspecies, which is compatible with a history of C-derived introgression. Yet, these colonies were classified with the highest probability (0.994) of the three subspecies. In the A. m. carnica range, 88.3% of the colonies matched this subspecies, with a probability of 0.984. The association between wing and molecular markers, assessed for 1214 colonies from the M-lineage range, was highly significant but not strong (r = 0.31, p < 0.0001). The agreement between the markers was influenced by C-derived introgression, with the best results obtained for colonies with high genetic integrity. This study indicates the good performance of DeepWings© on a realistic wing image dataset.

Wing measurements are a possible tool for the identification of European forensically important Sarcophagidae

The flesh flies are a group of insects well known for their forensic importance. Reliable identification of these flies relies on the use of either molecular markers or the morphology of the male genital apparatus. Identification of female flesh flies is more time consuming and less reliable than their male counterparts. This is particularly problematic for forensic entomology practitioners, because female flesh flies are more abundant than males in carrion arthropod assemblages. As such, it is critical that alternative methods for flesh fly identification are established that are equally effective for both sexes. One promising technique is the use of wing measurements, which have been shown to be reliable for the identification of some groups of necrophagous Diptera from several geographical regions. We applied this method to the European Sarcophagidae for the first time, using a dataset of 881 specimens representing 29 species and 5 genera. Species identifications were based on 15 landmarks located at wing vein junctions. We also combined our results with data from previous studies of Calliphoridae and Muscidae which utilised the same methodology, enabling the testing of family level identification using wing morphometrics. Species identifications using wing measurements had varied success. While some species were successfully identified without error, others, particularly from the genus Sarcophaga, were often misclassified. Notably, in several species wing measurements successfully identified both males and females. The results presented here suggest that wing measurements are a promising complementary method to other methods for the identification of necrophagous Sarcophagidae especially in material unsorted at the family level. It can also be used to double check identification performed by a taxonomist using traditional methods.

Geographical Variation of Honey Bee (Apis mellifera L. 1758) Populations in South-Eastern Morocco: A Geometric Morphometric Analysis

Simple Summary

Western honey bees are of high importance to human food security as they provide valuable contributions through pollination. Unfortunately, high levels of honey bee colony losses have been registered around the world recently. One of the major reasons for these losses is the hybridization with non-native subspecies which leads to the loss of adaptation to local climatic conditions. In fact, it is proven that honey bee subspecies that are native to a certain area subsist better than imported ones. In this study, we investigate the conservation status and the geographic variation of four populations of Apis mellifera sahariensis in south-eastern Morocco using the geometric morphometric approach. The results obtained have indicated that our samples were significantly different from the two subspecies used as reference (Apis mellifera sahariensis, Apis mellifera intermissa) which could be explained by a hybridization phenomenon occurring in the study area. The four populations studied were significantly different in terms of wing shape. These differences were mainly due to the fragmented distribution of the study area. Results of this study can be used in the planning of future strategies for the conservation of the Saharan honey bee in Morocco.

Abstract

In Morocco, there are two well-recognised honey bee (Apis mellifera L.) subspecies: A. m. intermissa in the north and A. m. sahariensis in the south-east. The latter subspecies is found in the arid and semiarid climates of the Sahara Desert. In this study, we used honey bees from four areas of south-eastern Morocco which are, to some degree, isolated by arid zones. We analysed the shape and size of the forewings, using the method of geometric morphometrics. The bees from the four areas of south-eastern Morocco differed significantly in terms of wing shape. Moreover, bees from traditional hives were smaller than those from modern hives. The bees from south-eastern Morocco were clearly different from the reference samples obtained from the Morphometric Bee Data Bank in Oberursel, Germany, representing most of the global variation in honey bees. Surprisingly, the bees were also different from A. m. sahariensis, which should occur in the study area, according to earlier studies. This difference could have been caused by introgression with non-native subspecies imported by beekeepers. The distinct honey bees from south-eastern Morocco deserve to be protected. We provide a method for identifying them, which can help protect them.

Historical Changes in Honey Bee Wing Venation in Romania

Simple Summary

Honey bees, in addition to producing honey, are important pollinators of wild and cultivated plants. Unfortunately, in some places, the population of honey bees is declining. One of the factors that affect their survival is adaptation to the local environment. Bees native to a particular area survive better than those imported. Despite this fact, some beekeepers import non-native bees and use them in their apiaries. Imported bees produce hybrids with bees from surrounding colonies because beekeepers do not control their mating. In consequence, the whole population can change. In this study, we verified how the population of Romanian bees has changed over the last four decades. We found significant temporal changes in wing venation. Despite these changes, the two major subpopulations of bees separated by mountains remain distinct. We provide a tool for the easy identification of native bees from Romania, which can help to protect them.

Abstract

The honey bee (Apis mellifera) is an ecologically and economically important species that provides pollination services to natural and agricultural systems. The biodiversity of the honey bee is being endangered by the mass import of non-native queens. In many locations, it is not clear how the local populations have been affected by hybridisation between native and non-native bees. There is especially little information about temporal changes in hybridisation. In Romania, A. m. carpatica naturally occurs, and earlier studies show that there are two subpopulations separated by the Carpathian Mountains. In this study, we investigated how the arrangement of veins in bees’ wings (venation) has changed in Romanian honey bees in the last four decades. We found that in the contemporary population of Romanian bees, there are still clear differences between the intra- and extra-Carpathian subpopulations, which indicates that natural variation among honey bees is still being preserved. We also found significant differences between bees collected before and after 2000. The observed temporal changes in wing venation are most likely caused by hybridisation between native bees and non-native bees sporadically introduced by beekeepers. In order to facilitate conservation and the monitoring of native Romanian bees, we developed a method facilitating their identification.

Climatic oscillations in Quaternary have shaped the co-evolutionary patterns between the Norway spruce and its host-associated herbivore

During the Last Glacial Maximum in the Northern Hemisphere, expanding ice sheets forced a large number of plants, including trees, to retreat from their primary distribution areas. Many host-associated herbivores migrated along with their host plants. Long-lasting geographic isolation between glacial refugia could have been led to the allopatric speciation in separated populations. Here, we have studied whether the migration history of the Norway spruce Picea abies in Quaternary has affected its host-associated herbivorous beetle—Monochamus sartor. By using microsatellite markers accompanied by the geometric morphometrics analysis of wing venation, we have revealed the clear geographic structure of M. sartor in Eurasia, encompassing two main clusters: southern (Alpine–Carpathian) and eastern (including northeastern Europe and Asia), which reflects the northern and southern ecotypes of its host. The two beetles’ lineages probably diverged during the Pleniglacial (57,000—15,000 BC) when their host tree species was undergoing significant range fragmentation and experienced secondary contact during post-glacial recolonization of spruce in the Holocene. A secondary contact of divergent lineages of M. sartor has resulted in the formation of the hybrid zone in northeastern Europe. Our findings suggest that the climatic oscillations during the Pleistocene have driven an insect-plant co-evolutionary process, and have contributed to the formation of the unique biodiversity of Europe.

Body mass but not wing size or symmetry correlates with life span of honey bee drones

In social insects such as the honey bee, the quality of drones at the time of their emergence can affect their maintenance in the colony until maturity. Body mass, wing size and wing asymmetry of emerging honey bee drones were measured and correlated with their life span in the colony and compared between individuals reaching maturity or not. The life span of drones differed among colonies in which they were maintained after emergence but not between colonies in which they were reared. More drones heavier at emergence reached sexual maturity at 15 days and had a longer life span compared with light-weight drones of lower mass. The size and symmetry of drone forewings was not correlated with their life span. Our results suggest that body mass at emergence is a good predictor of drone survival in the colony.

Honey bees are larger and live longer after developing at low temperature

Honey bees (Apis mellifera) are known to be temperature specialist and actively maintain brood temperature in a very narrow temperature range. Developing larvae are sensitive to changes of temperature in the nest. Temperatures lower than generally assumed as optimal have been shown to cause a number of negative developmental and behavioural changes in honey bees. We have reared both worker and drone larvae during the capped brood stage in cold (32 °C) and in warm temperatures (35 °C). Next, we measured their body mass at emergence and the longevity of individuals either caged in incubator (workers) or placed in maintaining colonies (drones). For drones, the reproductive caste, we also compared the mass and ratio of body parts (head, thorax, and abdomen) to body mass. As expected, both castes were heavier when reared in cold, but contrary to our expectations, both castes survived longer after emergence than bees reared in warm. Drones reared in cold were characterized by proportionally larger abdomens, in comparison to drones reared in warm.

Developmental Costs of Biological Invasion: The Exotic Wood Borer Tetropium fuscum (Coleoptera: Cerambycidae) is More Asymmetric and Smaller in Invaded Area

Biological invasions provide a unique opportunity to gain insight into basic biological processes occurring under new circumstances. During the process of establishment, exotic species are exposed to various stressors which may affect their development. Presence of the stressors is often detected by measurements of left-right body asymmetry, which consists of two main components: fluctuating asymmetry and directional asymmetry. Fluctuating asymmetry constitutes random differences between the two body sides, whereas directional asymmetry occurs when a particular trait is bigger on one of the sides. The relation between these two asymmetry components is still not fully understood. Our goal was to investigate the potential differences in asymmetry patterns between native and invasive populations of Tetropium fuscum (Fabr. 1787) (Coleoptera: Cerambycidae), a harmful forest pest native to Europe and introduced to North America. Wing asymmetry assessment was based on the geometric morphometrics of hind wings. We found that specimens from invaded area were markedly smaller and have more asymmetric wings than individuals from native population, suggesting some unfavorable conditions in the invaded area. Moreover, we found significant directional asymmetry in the native but not in the invasive population. On the other hand, differences between left and right hind wings were similar in the native and invasive populations, in terms of direction. This suggests that a high level of fluctuating asymmetry in the invasive population may blur the intrinsic directional asymmetry and hinder its detection. Our data show that fluctuating asymmetry has a potential as an indicator of developmental stress in invasive species.

DKey software for editing and browsing dichotomous keys

Despite advances in computer technology and the increasing availability of multiple-access taxonomic keys, traditional dichotomous keys remain the most often used taxonomic identification tools. On the other hand, there seems to be a lack of an editor of dichotomous keys, which is both freely available and easy to use. The DKey software was developed in order to alleviate this problem. A taxonomic key in text format can be imported to the software in order to edit it. Various editing options are possible, including: moving couplets, removing couplets, combining keys and renumbering keys. The software can output the key either in the traditional text format, ready for publication in a scientific journal, or in hypertext linked format, which makes identification faster and easier, due to the fact that pointers can be clicked in order to move to the next couplet. The DKey software should be useful for both taxonomic experts creating keys and those who use them for identification. The DKey software is freely available and open source.

Elytra reduction may affect the evolution of beetle hind wings

Beetles are one of the largest and most diverse groups of animals in the world. Conversion of forewings into hardened shields is perceived as a key adaptation that has greatly supported the evolutionary success of this taxa. Beetle elytra play an essential role: they minimize the influence of unfavorable external factors and protect insects against predators. Therefore, it is particularly interesting why some beetles have reduced their shields. This rare phenomenon is called brachelytry and its evolution and implications remain largely unexplored. In this paper, we focused on rare group of brachelytrous beetles with exposed hind wings. We have investigated whether the elytra loss in different beetle taxa is accompanied with the hind wing shape modification, and whether these changes are similar among unrelated beetle taxa. We found that hind wings shape differ markedly between related brachelytrous and macroelytrous beetles. Moreover, we revealed that modifications of hind wings have followed similar patterns and resulted in homoplasy in this trait among some unrelated groups of wing-exposed brachelytrous beetles. Our results suggest that elytra reduction may affect the evolution of beetle hind wings.

Forewing structure of the solitary bee Osmia bicornis developing on heavy metal pollution gradient

Wild bees in natural conditions can develop under various environmental stressors. Heavy metal pollution of the environment is one of the most widely studied stressors in insects, yet its effect is poorly described in bees. We have measured how pollution of the environment along a zinc, cadmium and lead contamination gradient in Poland affects bee development, using red mason bees (Osmia bicornis) as a model and their forewing asymmetry measures to assess possible developmental instabilities. We have also described wing asymmetry measures in the red mason bee-an important managed pollinator species-for the first time. The development of bee larvae in a contaminated environment did not affect forewing asymmetry measures, but it did lead to a negative correlation of wing size with contamination in females. Bees also showed a clear change in their asymmetry measures between various seasons, suggesting other, unknown environmental factors affecting wing asymmetry more than pollution. Sexes were found to have different forewing shape and size, larger females having larger forewings than the smaller males. The direction of size asymmetry was in favour of the left side in both sexes and also shape differences between the left and right wings showed similar tendencies in males and females. The levels of forewing shape and size asymmetry were smaller in females, making them the more symmetrical sex.

Identification of Muscidae (Diptera) of medico-legal importance by means of wing measurements

Cadavers attract numerous species and genera of Muscidae, both regular elements of carrion insect assemblages, and accidental visitors. Identification of adult Muscidae may be considered difficult, particularly by non-experts. Since species identification is a vital first step in the analysis of entomological material in any forensic entomology orientated experiment and real cases, various alternative methods of species identification have been proposed. We investigated possibility of semiautomated identification by means of wing measurements as an alternative for classic morphology and DNA-based approaches. We examined genus-level identification success for 790 specimens representing 13 genera of the most common European cadavers visiting Muscidae. We found 99.8% of examined specimens correctly identified to the genus-level. Without error, the following were identified: Azelia, Eudasyphora, Graphomya, Hydrotaea, Musca, Muscina, Mydaea, Neomyia, Polietes, Stomoxys and Thricops. Genus-level misidentifications were found only in Helina and Phaonia. Discrimination of examined material on the species level within Hydrotaea (318 specimens representing eight species) and Muscina (163 specimens representing four species) showed lower, yet still high average identification success, 97.2 and 98.8%, respectively. Our results revealed relatively high success in both genus and species identification of Muscidae of medico-legal importance. Semiautomated identification by means of wing measurements can be used by non-experts and does not require sophisticated equipment. This method will facilitate the identification of forensically relevant muscids in comparison to more difficult and more time-consuming identification approaches based on taxonomic keys or DNA-based methods. However, for unambiguous identification of some taxa, we recommend complementary use of identification keys.

Hind wing morphology facilitates discrimination between two sibling species: <i>Leiopus</i> <i>nebulosus</i> and <i>L. linnei</i> (Coleoptera: Cerambycidae)

The study focused on two sibling beetle species: Leiopus nebulosus (Linnaeus, 1758) and L. linnei Wallin, Nylander & Kvamme, 2009. These species are very similar morphologically and their identification is difficult and possible only by experienced taxonomists. A supporting method for identification of L. nebulosus and L. linnei based on hind wings measurements was developed. The study was based on 115 specimens of L. linnei and 45 specimens of L. nebulosus. The correctness of identification of L. nebulosus amounted to 95.56%, and of L. linnei - 97.39%. The obtained model facilitates reliable identification of L. nebulosus and L. linnei also by less experienced entomologists. Geographical distributions of both species were summarized based on faunistic data from 39 scientific papers. The results show that both species have a Western-Palearctic distribution. Their distribution ranges are markedly overlapping. However, L. linnei is the species reported from larger number of localities, and observed more often.

The relationship between asymmetry, size and unusual venation in honey bees (Apis mellifera)

Despite the fact that symmetry is common in nature, it is rarely perfect. Because there is a wide range of phenotypes which differs from the average one, the asymmetry should increase along with deviation. Therefore, the aim of this study was to assess the level of asymmetry in normal individuals as well as in phenodeviants categorized as minor or major based on abnormalities in forewing venation in honey bees. Shape fluctuating asymmetry (FA) was lower in normal individuals and minor phenodeviants compared with major phenodeviants, whereas the former two categories were comparable in drones. In workers and queens, there were not significant differences in FA shape between categories. FA size was significantly lower in normal individuals compared with major phenodeviant drones and higher compared with minor phenodeviant workers. In queens, there were no significant differences between categories. The correlation between FA shape and FA size was significantly positive in drones, and insignificant in workers and queens. Moreover, a considerable level of directional asymmetry was found as the right wing was constantly bigger than the left one. Surprisingly, normal individuals were significantly smaller than minor phenodeviants in queens and drones, and they were comparable with major phenodeviants in all castes. The correlation between wing size and wing asymmetry was negative, indicating that smaller individuals were more asymmetrical. The high proportion of phenodeviants in drones compared with workers and queens confirmed their large variability. Thus, the results of the present study showed that minor phenodeviants were not always intermediate as might have been expected.

Preemptive defensive self-sacrifice by ant workers

Worker insects altruistically sacrifice their own reproduction to rear nondescendant kin. This sacrifice reaches its most spectacular level in suicidal colony defense. Suicidal defense, such as when the sting of a honeybee worker embeds in a predator and then breaks off, is normally a facultative response. Here we describe the first example of preemptive self-sacrifice in nest defense. In the Brazilian ant Forelius pusillus, the nest entrance is closed at sunset. One to eight workers finish the job from the outside and, in doing so, sacrifice their lives.

Semiautomated Identification of European Corn Borer (Lepidoptera: Crambidae)

The European corn borer Ostrinia nubilalis (Hübner, 1796) is a serious and widely studied pest of corn. The most common method of its control is by means of insecticides. However, biological control is becoming more and more popular. The hymenopteran parasitoid Trichogramma sp. is the most promising and effective one among the biological agents and is now widely used in North America and Europe. Its application should occur at the time when the European corn borer is at the beginning of the eggs laying period. However, the discrimination between the European corn borer and some other species occurring in agricultural landscapes at the same time can be difficult, especially for farmers which are neither familiar with the morphological nor molecular methods of identification. The scope of this study is to test the ability of the automatic computer equipment to determine the European corn borer and to separate it from the most common Lepidoptera pests found in corn plantations. The experiment showed that the 97.0% of the 247 specimens belonging to four common pestlepidopterans were correctly classified by the use of a personal computer, desktop scanner, and the special software. The obtained results showed that this technique based on wing measurements can be an effective tool for monitoring of the European corn borer. In the future, this method can be used by farmers to identify this pest and apply control measures at optimal time.

Within- and Between-Species Variation of Wing Venation in Genus Monochamus (Coleoptera: Cerambycidae)

We have described the morphological variation of five Western Palaearctic species of Monochamus Dejean, 1821. The variation was assessed using wing measurements. Special emphasis was placed on the differences between Monochamus sartor (F., 1787) and Monochamus urussovii (Fischer-Waldheim, 1805). There was an interesting pattern of variation between the two species. Individuals of M. sartor from the Carpathians differed markedly from individuals of M. urussovii from Siberia, but individuals from north-eastern Poland were intermediate between those two populations. The intermediate individuals were more similar to the Siberian M. urussovii than to the Carpathian M. sartor despite the relatively large geographic distance between north-eastern Poland and Siberia. The occurrence of the intermediate individuals in north-eastern Poland may be the effect of hybridization between M. urussovii and M. sartor, which might have occurred after secondary contact between the two species in the Holocene.

Non-transferable signals on ant queen eggs

How biological systems resolve internal conflicts is a major evolutionary question. Social insect workers cooperate but also pursue individual interests, such as laying male eggs. The rewards of this individual selfishness can be reduced by policing, such as by killing worker-laid eggs. However, selfish individuals may evade policing. What factors prevent individuals from being able to evade policing? In the ant Pachycondyla inversa, workers kill (police) worker-laid eggs. Because the colony keeps eggs in piles and worker-laid and queen-laid eggs are chemically distinct, worker-laid eggs might become more acceptable once placed in the egg pile by odour transfer from touching queen-laid eggs. Here, we show that such "cue scrambling" does not occur. Worker-laid eggs that were sandwiched between three queen-laid eggs for 45 min were not more acceptable in a policing bioassay than control worker-laid eggs. Chemical analyses also showed that the surface hydrocarbon profile of these eggs was unchanged. Policing, therefore, is stable against this potential cheating mechanism probably because queen-laid eggs are made chemically distinct using chemicals, that are not easily transferred by physical contact.

Influence of caste polyethism on longevity of workers in social insect colonies

Different patterns of division of labor can affect the expected longevity of social insects workers. It has been earlier suggested that when tasks performed inside and outside colony are equally risky then the expected longevity of workers in colonies with caste polyethism is greater than that in colonies without polyethism. To verify these predictions I used a model assuming two sets of tasks, associated with different mortality rates. In the colony without polyethism the workers preformed safe and risky tasks in turn, while in the colony with caste polyethism the workers specialized in only one set of tasks. The outcomes suggest that the expected longevity of workers in colonies with caste polyethism cannot be greater than that in colonies without polyethism. Only if there is no aging and under some special and rare conditions are there no differences in expected longevity between colonies with and without caste polyethism. If aging is independent of activity, caste polyethism does not shorten longevity when all tasks in the colony are equally risky. The results can explain why caste polyethism is not as widespread among social insects as age polyethism.

A test of worker policing theory in an advanced eusocial wasp, Vespula rufa

Mutual policing is an important mechanism for maintaining social harmony in group-living organisms. In some ants, bees, and wasps, workers police male eggs laid by other workers in order to maintain the reproductive primacy of the queen. Kin selection theory predicts that multiple mating by the queen is one factor that can selectively favor worker policing. This is because when the queen is mated to multiple males, workers are more closely related to queen's sons than to the sons of other workers. Here we provide an additional test of worker policing theory in Vespinae wasps. We show that the yellowjacket Vespula rufa is characterized by low mating frequency, and that a significant percentage of the males are workers' sons. This supports theoretical predictions for paternities below 2, and contrasts with other Vespula species, in which paternities are higher and few or no adult males are worker produced, probably due to worker policing, which has been shown in one species, Vespula vulgaris. Behavioral observations support the hypothesis that V. rufa has much reduced worker policing compared to other Vespula. In addition, a significant proportion of worker-laid eggs were policed by the queen.

DrawWing, a program for numerical description of insect wings

There is usually a pattern of veins on an insect wing. This pattern is species-specific and is used taxonomically. For example, the coordinates of some characteristic points on the wing are used to compare vein patterns. The characteristic points are often vein junctions or vein ends. A tool is presented that enables automatic identification of vein junctions. An image of an insect wing is used to determine the wing outline and veins. The vein skeleton is obtained using a thinning algorithm. Bezier splines are fitted to both the wing outline and the vein skeleton. The splines are saved in an encapsulated postscript file. Another output file in text format contains the coordinates of vein junctions. Both the program and its source code are available under GNU General Public License at [www.cyf-kr.edu.pl/~rotofils/drawwing.html]. The program presented in this paper automatically provides a numerical description of an insect wing. It converts an image of an insect wing to a list of coordinates of vein junctions, and a wing diagram that can be used as an illustration. Coordinates of the vein junctions extracted by the program from wing images were used successfully to discriminate between males of Dolichovespula sylvestris and Dolichovespula saxonica.

Senescence and learning in honeybee (Apis mellifera) workers

Foraging by honeybee workers was investigated from the moment of the first foraging flight until death. To minimise the influence of factors other than senescence the foragers were trained to collect food from an artificial flower close to their hive. During each foraging trip the workers repeatedly visited an artificial flower, collecting one microlitre of 50% sugar solution per visit. During the first 50 flights the mean time taken to collect one portion of food decreased significantly and the number of visits to the artificial flower per flight increased significantly. During flights following the 50th flight, the mean time taken to collect one portion of food increased significantly and the number of visits to the artificial flower per flight decreased significantly. The results confirm earlier observations that the foraging behaviour of honeybee workers is not only influenced by learning, but also by the effects of senescence.