Perhaps the most valuable single set of resources for genetic studies of Drosophila melanogaster is the collection of multiply-inverted chromosomes commonly known as balancer chromosomes. Balancers prevent the recovery of recombination exchange products within genomic regions included in inversions and allow perpetual maintenance of deleterious alleles in living stocks and the execution of complex genetic crosses. Balancer chromosomes have been generated traditionally by exposing animals to ionizing radiation and screening for altered chromosome structure or for unusual marker segregation patterns. These approaches are tedious and unpredictable, and have failed to produce the desired products in some species. Here I describe transgenic tools that allow targeted chromosome rearrangements in Drosophila species. The key new resources are engineered reporter genes containing introns with yeast recombination sites and enhancers that drive fluorescent reporter genes in multiple body regions. These tools were used to generate a doubly-inverted chromosome 3R in D. simulans that serves as an effective balancer chromosome.

We characterize a newly discovered morphological difference between species of the Drosophila melanogaster subgroup. The muscle of Lawrence (MOL) contains about four to five fibers in D. melanogaster and Drosophila simulans and six to seven fibers in Drosophila mauritiana and Drosophila sechellia. The same number of nuclei per fiber is present in these species but their total number of MOL nuclei differs. This suggests that the number of muscle precursor cells has changed during evolution. Our comparison of MOL development indicates that the species difference appears during metamorphosis. We mapped the quantitative trait loci responsible for the change in muscle fiber number between D. sechellia and D. simulans to two genomic regions on chromosome 2. Our data eliminate the possibility of evolving mutations in the fruitless gene and suggest that a change in the twist might be partly responsible for this evolutionary change.

As most of us are aware, today's primary school, high school and undergraduate biology programs are struggling to incorporate even a fraction of the 'molecular revolution'of biological knowledge and technologies that surround us. In the first term alone, life science and biology classes of the new millennia routinely cover condensed versions of the year-long classes taught in the 60s, 70s and 80s. Teachers no longer have the luxury of spending half a year presenting Mendel and his peas.

Male orchid bees of the species Eulaema meriana buzz their wings while stationary at territory perches. During buzzing, wings are first positioned laterally and then moved in a plane parallel to the ground, which probably generates a substantial airflow past the body. Within a perching episode, the ratio of buzz to pause duration decreases nonlinearly. The incidence of wing buzzing increases with ambient temperature and with duration of activity. Bees never defended territories when ambient temperatures exceeded 28.5°C. Wing buzzing may be a visual or acoustic display to conspecifics, although the brightly colored abdomen is never obscured by the wings during buzzing, and the sounds of wing buzzing are low in amplitude. The increase in buzzing frequency with increased ambient temperature and the nonlinear decrease in buzz to pause duration during perching suggest that wing buzzing may be a thermoregulatory mechanism.

Many species of insects display dispersing and nondispersing morphs. Among these, aphids are one of the best examples of taxa that have evolved specialized morphs for dispersal versus reproduction. The dispersing morphs typically possess a full set of wings as well as a sensory and reproductive physiology that is adapted to flight and reproducing in a new location. In contrast, the nondispersing morphs are wingless and show adaptations to maximize fecundity. In this review, we provide an overview of the major features of the aphid wing dimorphism. We first provide a description of the dimorphism and an overview of its phylogenetic distribution. We then review what is known about the mechanisms underlying the dimorphism and end by discussing its evolutionary aspects.