Cataloging the very large number of undescribed species of insects could be greatly accelerated by automated DNA based approaches, but procedures for large-scale species discovery from sequence data are currently lacking. Here, we use mitochondrial DNA variation to delimit species in a poorly known beetle radiation in the genus Rivacindela from arid Australia. Among 468 individuals sampled from 65 sites and multiple morphologically distinguishable types, sequence variation in three mtDNA genes (cytochrome oxidase subunit 1, cytochrome b, 16S ribosomal RNA) was strongly partitioned between 46 or 47 putative species identified with quantitative methods of species recognition based on fixed unique ("diagnostic") characters. The boundaries between groups were also recognizable from a striking increase in branching rate in clock-constrained calibrated trees. Models of stochastic lineage growth (Yule models) were combined with coalescence theory to develop a new likelihood method that determines the point of transition from species-level (speciation and extinction) to population-level (coalescence) evolutionary processes. Fitting the location of the switches from speciation to coalescent nodes on the ultrametric tree of Rivacindela produced a transition in branching rate occurring at 0.43 Mya, leading to an estimate of 48 putative species (confidence interval for the threshold ranging from 47 to 51 clusters within 2 logL units). Entities delimited in this way exhibited biological properties of traditionally defined species, showing coherence of geographic ranges, broad congruence with morphologically recognized species, and levels of sequence divergence typical for closely related species of insects. The finding of discontinuous evolutionary groupings that are readily apparent in patterns of sequence variation permits largely automated species delineation from DNA surveys of local communities as a scaffold for taxonomy in this poorly known insect group.

The effect of egg density on establishment and dispersal of larvae of the western corn rootworm, Diabrotica virgifera virgifera LeConte, was evaluated in a 3-yr field study. Implications of these data for resistance management plans for Bt crops are discussed. Viable egg levels of 100, 200, 400, 800, and 1600 eggs per infested plant were evaluated in 2000, 2001, and 2002. A 3200 viable egg level was also tested in 2001 and 2002. All eggs were infested on one plant per subplot in a field that was planted to soybean, Glycine max (L.), in the previous year. For each subplot, the infested plant, three plants down the row, the closest plant in the adjacent row of the plot, and a control plant at least 1.5 m from any infested plant (six plants total) were sampled. In 2000, there were five sample dates between egg hatch and pupation, and in 2001 and 2002, there were six sample dates. On each sample date, four replications of each egg density were sampled for both larval recovery and plant damage. Initial establishment on a corn plant seemed to not be density-dependent because a similar percentage of larvae was recovered from all infestation rates. Plant damage and, secondarily, subsequent postestablishment larval movement were density-dependent. Very little damage and postestablishment movement occurred at lower infestation levels, but significant damage and movement occurred at higher infestation rates. Movement generally occurred at a similar time as significant plant damage and not at initial establishment, so timing of movement seemed to be motivated by available food resources rather than crowding. At the highest infestation level in 2001, significant movement three plants down the row and across the 0.76 m row was detected, perhaps impacting refuge strategies for transgenic corn.

If registered, transgenic corn, Zea mays L., with corn rootworm resistance will offer a viable alternative to insecticides for managing Diabrotica spp. corn rootworms. Resistance management to maintain susceptibility is in the interest of growers, the Environmental Protection Agency, and industry, but little is known about many aspects of corn rootworm biology required for an effective resistance management program. The extent of larval movement by the western corn rootworm, Diabrotica virgifera virgifera LeConte, that occurs from plant-to-plant or row-to-row after initial establishment was evaluated in 1998 and 1999 in a Central Missouri cornfield. Post-establishment movement by western corn rootworm larvae was clearly documented in two of four treatment combinations in 1999 where larvae moved up to three plants down the row and across a 0.46-m row. Larvae did not significantly cross a 0.91-m row after initial host establishment in 1998 or 1999, whether or not the soil had been compacted by a tractor and planter. In the current experiment, western corn rootworm larvae moved from highly damaged, infested plants to nearby plants with little to no previous root damage. Our data do not provide significant insight into how larvae might disperse after initial establishment when all plants in an area are heavily damaged or when only moderate damage occurs on an infested plant. A similar situation might also occur if a seed mixture of transgenic and isoline plants were used and if transgenic plants with rootworm resistance are not repellent to corn rootworm larvae.

Tiger beetles are a remarkable group that captivates amateur entomologists, taxonomists and evolutionary biologists alike. This diverse clade of beetles comprises about 2300 currently described species found across the globe. Despite the charisma and scientific interest of this lineage, remarkably few studies have examined its phylogenetic relationships with large taxon sampling. Prior phylogenetic studies have focused on relationships within cicindeline tribes or genera, and none of the studies have included sufficient taxon sampling to conclusively examine broad species patterns across the entire subfamily. Studies that have attempted to reconstruct higher-level relationships of Cicindelinae have yielded conflicting results. Here, we present the first taxonomically comprehensive molecular phylogeny of Cicindelinae to date, with the goal of creating a framework for future studies focusing on this important insect lineage. We utilized all available published molecular data, generating a final concatenated dataset including 328 cicindeline species, with molecular data sampled from six protein-coding gene fragments and three ribosomal gene fragments. Our maximum-likelihood phylogenetic inferences recover Cicindelinae as sister to the wrinkled bark beetles of the subfamily Rhysodinae. This new phylogenetic hypothesis for Cicindelinae contradicts our current understanding of tiger beetle phylogenetic relationships, with several tribes, subtribes and genera being inferred as paraphyletic. Most notably, the tribe Manticorini is recovered nested within Platychilini including the genera Amblycheila Say, Omus Eschscholtz, Picnochile Motschulsky and Platychile Macleay. The tribe Megacephalini is recovered as paraphyletic due to the placement of the monophyletic subtribe Oxycheilina as sister to Cicindelini, whereas the monophyletic Megacephalina is inferred as sister to Oxycheilina, Cicindelini and Collyridini. The tribe Collyridini is paraphyletic with the subtribes Collyridina and Tricondylina in one clade, and Ctenostomina in a second one. The tribe Cicindelini is recovered as monophyletic although several genera are inferred as para-or polyphyletic. Our results provide a novel phylogenetic framework to revise the classification of tiger beetles and to encourage the generation of focused molecular datasets that will permit investigation of the evolutionary history of this lineage through space and time.

The effect of egg density on establishment and dispersal of larvae of the western corn rootworm, Diabrotica virgifera virgifera LeConte, was evaluated in a 3-yr field study. Implications of these data for resistance management plans for Bt crops are discussed. Viable egg levels of 100, 200, 400, 800, and 1600 eggs per infested plant were evaluated in 2000, 2001, and 2002. A 3200 viable egg level was also tested in 2001 and 2002. All eggs were infested on one plant per subplot in a field that was planted to soybean, Glycine max (L.), in the previous year. For each subplot, the infested plant, three plants down the row, the closest plant in the adjacent row of the plot, and a control plant at least 1.5 m from any infested plant (six plants total) were sampled. In 2000, there were five sample dates between egg hatch and pupation, and in 2001 and 2002, there were six sample dates. On each sample date, four replications of each egg density were sampled for both larval recovery and plant damage. Initial establishment on a corn plant seemed to not be density-dependent because a similar percentage of larvae was recovered from all infestation rates. Plant damage and, secondarily, subsequent postestablishment larval movement were density-dependent. Very little damage and postestablishment movement occurred at lower infestation levels, but significant damage and movement occurred at higher infestation rates. Movement generally occurred at a similar time as significant plant damage and not at initial establishment, so timing of movement seemed to be motivated by available food resources rather than crowding. At the highest infestation level in 2001, significant movement three plants down the row and across the 0.76 m row was detected, perhaps impacting refuge strategies for transgenic corn.