No description available.

No description available.

No description available.

Social Hymenopterans such as bees, wasps and ants have developed sophisticated and effective communication among nestmates. Their remarkable ability to perform certain task such as in navigation suggests that these animals are able to learn and process the information they have gathered. Here, I test for such abilities in tandem running recruitment whereby an informed ant leads a na'ive ant to a resource and tactile cues are used by the follower ants to prompt the leader ants to move forward after a pause. The experiments presented here show that in addition to tactile signals being used, chemical signals are also being laid on the substrate by the leader ants mainly to maintain the bond between the tandem run pairs until they reach the goal. Both leader and follower ants learn visual cues during tandem running. The ants learn landmarks as well as the position of parallel wall edges and use this information to guide them in navigation to and from their nest. Furthermore, this information is updated on subsequent journeys making experienced ants better at navigation than newly recruited ants. Finally, I show that when communication between tandem running ants is manipulated experimentally by a dummy leader, many followers are not able to return to their old nest after having been led much quicker than the normal speed of tandem running. I hypothesize that this is due to the lack of learning opportunities and information gathering by the follower ants during such experimentally manipulated tandem running. Overall, my results strongly suggest that the navigational strategies of tandem running ants involve cognitive abilities. Ants, despite having small brains, are able to learn and process the information they gather to help them navigate efficiently in unpredictable environmental conditions.

The rules underlying the formation of complex patterns have been at the centre of several research fields. In Biology, understanding what brings animal groups together and how they maintain group cohesion has received a fair amount of attention. This thesis focuses on these processes in social insects, in particular we study collective decision making in Temnothorax albipennis ant colonies. These colonies inhabit rock crevices, whose fragility leads to frequent colony emigrations. Hence, individuals must be able to choose an appropriate target nest and reach a consensus whilst maintaining the group together. Interestingly, colonies also emigrate to new homes even if their current nest remains intact, whenever the value increase in relation to their current home compensates for the risks and costs of emigrating. We further investigate these move-to-improve emigrations by analysing how housing conditions affect both the exploration and emigration dynamics. The results presented, show (1) how colonies adjust their nest searching effort with regard to the value of their current home and (2) how, both the decision to upgrade to a better home and how much effort to put into the search for a higher quality nest is driven by flexibility both at the collective and individual level, (3) with experience being crucial for efficient task performance. Animals in groups are able to achieve a lot more than the sum of the efforts of each individual working alone, however, one should not underestimate the capacities of each individual. Further research should focus on how intelligent individuals contribute effectively to collective intelligence.

Lasius flavus F. is a common ant species on chalk grasslands in the south of England. This thesis examines the effects of the management regimes and environmental conditions of these grasslands, on the characteristics of the ant populations. The null hypothesis of the study was that the characteristics of L. flavus populations are not significantly affected by variation in: 1) management procedures, 2) the physical environment, 3) the biological environment. The ant populations, management regimes and environmental characteristics of twenty sample areas were investigated and subjected to intensive analysis to examine this hypothesis. The null hypothesis was rejected. The population of ants that an area of chalk grassland supports, depends on both the management of that area and the environmental conditions. In the short term (2 to 4 years) more intense management leads to significant reductions in the sizes of the soil mounds built by the ant colonies, and reductions in the sexual productivity and sexual investment ratios of the colonies. In the longer term (over 10 years) the density of mounds is also reduced. The most important environmental characteristic of the grasslands is the soil water regime. Drier areas support a lower density of colonies with smaller mounds. The numbers of root aphids (the major food source of the ant) are reduced by increased grazing intensity. Other invertebrate groups are also affected by the management regime and the physical environment of the sample areas.

Bees use a wide range of senses to find flowers, detecting floral cues such as colour, shape, texture and fragrance. These floral cues allow bees to remember flowers that have been rewarding in the past and recall this information to identify con-specific flowers in the future. In this study, a previously unappreciated sensory modality in bumblebees (Bombus terrestris) is described: The detection of floral electric fields. These fields act as floral cues and can be used by bees to identify rewarding flowers while foraging. Like visual cues, floral electric fields exhibit variations in pattern and structure which can be discriminated by bees. Information from floral electric fields is shown to contribute to the complex array of floral stimuli that together facilitate learning and memory of floral rewards. A novel device for measuring the foraging activity of bees is described, and data generated by the device is used to determine under which atmospheric, meteorological and electrical conditions bees forage. The associated floral electric field strength under these conditions is calculated using a combination of atmospheric electric field data and finite element modelling techniques. Finite element models are used to design and validate experimental proxies for floral electric fields that are used to provide ecologically relevant electric field stimuli for behavioural and mechanical studies in the laboratory. Two putative electric field sensors, antennae and sensory hairs, are examined using laser Doppler vibrometry. Their mechanical sensitivity to a wide range of applied electric fields is measured. Both hairs and antennae show a mechanical response to floral-strength electric fields, though this response is between 2 and 11 times greater in magnitude than that of the antennae under identical stimulation. Hairs require a minimum stimulus voltage 5 times smaller than antennae. They show a mechanical response at roughly 2.5 times the distance from a given stimulus source when compared with antennae. This evidence combined with electrophysiological data from other authors strongly supports the hypothesis that bumblebees detect electric fields with mechanosensory body hairs.

No description available.

No description available.

No description available.