Two species of large carpenter bees (genus Xylocopa) were studied in southern Arizona. Nesting preference of X. c. arizonensis in floral scapes of Agave palmeri was found to depend on floral scape age and status of the thermal microenvironment. Evidence suggests that females assess scape age with extreme accuracy and this ability enables them to avoid those scapes that are degraded by other biota. Females also preferentially used Agave scapes that were shaded from the afternoon sunlight. Male mating behavior and lek site selection of X. varipuncta was also investigated near a large nesting site in a topographically flat area. Behaviors analyzed indicate that males tend to display singly and that they disperse pheromonal signals. Lek site selection was in accord with that found at three other study sites and further demonstrated that males did not clump their territories near nest sites. Distribution of male territories therefore does not appear to correspond to female distributions in the environment.

Biparental care in Hymenoptera is a little studied behaviour. This kind of parental care was discovered and the ethological aspect described in the bee Ceratina nigrolabiata from the Czech Republic and is well understood on the ethological level. However, biparental care is not a common behaviour and the lack of genomic studies of this behaviour complicates the understanding of the origin of the biparental care and its underlying pathways on the genomic and physiological level. This master's thesis presents the genome analyses of a biparental bee Ceratina nigrolabiata. It consists of a brief summary of the known parental behaviour across insects, characteristics of the genus Ceratina, summary of the used genomic methods and presents a candidate genes for the transcriptomic study of the biparental behaviour of Ceratina nigrolabiata. Key words: biparental care, genomics, Hymenoptera, Insecta, Ceratina, small carpenter bees

The interaction between Xylocopa californica and Chilopsis linearis was used to test the hypothesis that nectar robbing is costly to plants. No evidence for these costs, either in terms of decreased pollination or increased energy demands, was found. In fact, the mean number of seeds per fruit and the mean individual weight of seeds per fruit was higher from fruits that developed from robbed flowers than from fruits that developed from unrobbed flowers, indicating that the presence of Xylocopa californica enhanced pollination. Chilopsis linearis pollen was isolated from the tips of the abdomens of robbing Xylocopa californica and it was determined that these bees could be transferring pollen from flower to flower as they position themselves to rob. This association was found to be one of mutual benefit rather than one of exploitation.