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The objective of this study was to elucidate the nature and extent of drift by the aquatic insect populations of the Brazos River, Texas.

This thesis investigates chemical communication and decision making in a stingless bee (Tetragonisca angustula) and two species of ants (Lasius flavus and L. niger). Complex chemical signalling and seemingly elaborate behavioural patterns based upon decisions made by individuals of a colony have facilitated the evolution of social living in these insects. This thesis investigates two important features of social living that involve these features: nest mate recognition and navigation. The first part of this thesis (Chapter 3 and Appendix 3) investigates nestmate recognition and nest defence in the Neotropical stingless bee T. angustula. In Chapter 3, two mechanisms are investigated which could potentially facilitate the extremely efficient nest mate recognition system, previously demonstrated in this bee species. Both are found to play no role which will enable further work to focus on the few remaining possibilities. The second part of this thesis (chapters 4-6) focuses on navigational decision making in two common British ant species with contrasting ecologies. Chapter 4 investigates how L. niger foragers adapt to foraging at night when the visual cues, so important to these ants for diurnal foraging, are unavailable. This study showed that nocturnal foraging is achieved in these ants by increasing trail pheromone deposition while concomitantly switching to a greater reliance on these cues to navigate. Chapter 5 contrasts the navigational strategies and capabilities of L. niger with another Lasius ant species, L. flavus, and demonstrates how these species can flexibly switch dependency between available navigational cues to cope with foraging within a fluxional ecological environment. Finally, Chapter 6 focuses on the glandular components and trail pheromone of L. flavus by measuring behavioural responses to glandular constituents and identifying the glandular source of the trail pheromone. The aim was to also identify the trail pheromone(s) but due to time constraints this was not possible. However, a new methodology that simplifies the process of identifying trail pheromone components was developed and is described. Furthermore, this study has laid the foundations for further work to establish if the compound prevalent in the Dufour glands' of L. flavus does indeed serve as an antibacterial agent within the humid nest environment.

Signals are used to communicate resource-holding potential (RHP) to rivals during contests across a wide range of taxa. A controversial subset of RHP signals are status signals. In the last decade, research on North American populations of the paper wasp Polistes dominulus has provided evidence for a visual status signal based on variable clypeal patterns. However, observations of P. dominulus in its native European range indicate that the use of status signals across populations might be limited in this species. In Part I of this thesis (Chapters 3-5), I investigate status signalling in a Spanish population of P. dominulus. Using choice experiments, I show that clypeal patterns do not signal RHP in the Spanish population. Using large-scale field observations and microsatellite sequencing, I then show that patterns do not reflect individual quality in the wild. Together, these results strongly suggest that the clypeal pattern does not function in conflict resolution in the Spanish population. I conclude Part I by exploring the development of the clypeal patterns. I show that pattern expression is strongly temperature-dependent. This finding may provide an explanation for the variation in the signal value of clypeal patterns between populations. Contests among paper wasps are not limited to conspecific interactions, but may involve interactions with social parasites. In Parts II and III of this thesis (Chapters 6-7), I explore interactions between P. dominulus and the social parasite P. semenowi in the contexts of nest usurpation and conflict over reproduction. By experimentally staging usurpation contests, I show that neither parasites nor hosts gather information about rivals during nest usurpation. I then compare reproduction in parasitised and unparasitised colonies to test the predictions of competing models of reproductive skew. Incomplete control models receive qualified support; however, assumptions of skew models about players' information gathering abilities are questioned.