Evolution of the courtship display of Melittobia (Hymenoptera: Eulophidae).

Melittobia, a polyphagous pupal parasitoid of many solitary bees and wasps, has a complex courtship display, the evolutionary history of which is poorly understood. The current phylogeny of this genus suggests the complexity of the courtship has increased over time. We test this hypothesis using Bayesian and Maximum likelihood techniques to construct a molecular phylogeny of Melittobia-the first for this genus using modern techniques--using two intergenic regions (Internal Transcribed Spacer regions 1 and 2) and Cytochrome Oxidase 1 (CO1), and reconstruct the ancestral state of each major node in the phylogeny for five behaviors coincidental to major shifts in display complexity. We show that species-groups identified solely on behavioral characters are reliable, although the relationships among groups are different than those previously hypothesized. We also show that behaviors traditionally used in the courtship studies do not support a hypothesis of increasing display complexity over time.

The probable significance of tracheal tufts in the 8th abdominal segment of Heliothis virescens (F.) on the development of its parasitoid, Toxoneuron nigriceps (Viereck).

The 8th abdominal segment of Heliothis virescens (Fabricius) larvae contains aerating trachea and tracheole tufts that end in the hemocoel of the 8th segment, unlike the tracheae that invade tissues in other segments. These tracheal tufts from the 8th abdominal segment extend to the tokus region, which along with the telson cavity is known to act as a "lung" for hemocytes in Calpodes ethlius and a few other lepidopteran larvae. The goal of this research was to study the effects of these tracheal tufts in the 8th abdominal segment on parasitoid development inside the host larvae, H. virescens. The first objective was to determine if the eggs of the parasitoid, Toxoneuron nigriceps, are predominantly located among the tracheal tufts of the 8th abdominal segment compared to other body cavity regions irrespective of their oviposition site or the position of the host larvae. The results showed that several hours after oviposition most of the eggs are found in the 8th abdominal segment irrespective of the oviposition site or the position of the host larvae. The second objective was to study the effect of varying oxygen concentrations in vitro on various developmental stages of the egg. The results showed that decreasing oxygen concentrations adversely affects the parasitoid egg development in vitro. A third objective was to determine the oxygen concentration in 8th abdominal segment of the host larvae and compare it to other regions of the body using an oxygen sensor placed in vivo. The results suggested relatively high concentration of oxygen in the 8th abdominal segment compared to other regions of the host, thus supporting our hypothesis that the increased oxygen level in the 8th abdominal segment is important to the development of the parasitoid eggs.

Distribution and abundance of parasites of the rhodesgrass mealybug, Antonina graminis: reassessment of a classic example of biological control in the Southeastern United States.

Control of the rhodesgrass mealybug, Antonina graminis Maskell (Hemiptera: Pseudococcidae), by the encyrtid wasp Neodusmetia sangwani is considered a textbook example of classical biological control. However, recent evidence suggests that A. graminis is abundant in the southeastern United States and no recent surveys have been conducted to determine the status of N. sangwani or other A. graminis parasites. A survey was conducted and it was found that N. sangwani was uncommon overall, occurring at only 20 percent of survey sites. In addition, N. sangwani exhibited a patchy geographic distribution. Possible causes for these results are that N. sangwani has not dispersed widely since its introduction, or that the imported fire ant, Solenopsis invicta, is interfering with biological control. These results suggest that a reevaluation of the efficacy of biological control may be necessary. The survey also found two other encyrtid wasps utilizing A. graminis as a host. One, Acerophagus sp., is apparently native and was nearly as frequent as N. sangwani, while the other, Pseudectroma sp., is apparently introduced and relatively rare.

Differential gene expression between alate and dealate queens in the red imported fire ant, Solenopsis invicta Buren (Hymenoptera: Formicidae).

The transition of fire ant queens from alates to dealates, following a mating flight, is associated with numerous important physiological changes. A molecular analysis of gene expression differences that occur between alates and dealates was performed using the suppression subtractive hybridization (SSH) method. 983 SSH clones were arrayed and screened by dot blot hybridization, followed by Northern blot analysis for selected clones. Gene expression profiles throughout fire ant development were determined using semi-quantitative reverse transcriptase polymerase chain reactions (RT-PCR). The cytochrome c oxidase subunit II and STARS (striated muscle activator of Rho signaling) transcripts were expressed at higher levels in dealates compared to alates and may be involved in the programmed cell death of the flight muscles. Three different vitellogenin genes and two unique yellow g-like genes were identified that may be closely associated with the reproductive system and/or nutrient transport. Two putative antibacterial peptides, abaecin and hymenoptaecin precursors, were highly expressed in dealate queens, suggesting that they are present as an immune system component during this important stage of fire ant development. The genes identified in this study may be utilized as novel targets for fire ant control and will also provide molecular markers for studies of other social insects.

Sources of spores for the possible horizontal transmission of Thelohania solenopsae (Microspora: Thelohaniidae) in the red imported fire ants, Solenopsis invicta.

We screened adult and larval secretions and midden piles for the presence of Thelohania solenopsae spores to decipher potential sources for the horizontal transmission of the pathogen in fire ants. Hemolymph samples from both adult and larvae were also screened to rule out hemolymph contamination of samples. In adults, Thelohania spores were found in the crop and the fecal fluids, although only free spores were found in the fecal fluids of adults. In fourth instar larvae, both free and octospores were seen in midgut and the meconium samples. All of the midden pile samples had T. solenopsae spores of both types. Based on these results, we theorize that the pathogen may be horizontally transmitted within a colony by the removal and sharing of meconium of prepupating fourth instar larvae by adult workers and by the adult fecal droppings, and intercolonially by contamination of midden piles or brood raiding.

Prothoracic gland inactivation in Heliothis virescens (F.) (Lepidoptera:Noctuidae) larvae parasitized by Cardiochiles nigriceps Viereck (Hymenoptera:Braconidae).

Heliothis virescens (F.) last instar larvae parasitized by the endophagous braconid Cardiochiles nigriceps Viereck fail to attain the pupal stage, due to a parasitoid-induced alteration of ecdysteroid biosynthesis and metabolism. Currently available information on host prothoracic gland inactivation in this host-parasitoid system is reported here. Prothoracic glands of H. virescens mature larvae show a depressed biosynthetic activity, without undergoing gross morphological disruption. The ultrastructure of gland cells is characterized by minor parasitoid-induced changes, with the rough endoplasmic reticulum appearing more developed and electrondense than in nonparasitized controls. Eventually, the cells of prothoracic glands of parasitized host last instar larvae die but maintain their structural integrity. The inactivation of pupally committed host prothoracic glands is achieved through the disruption of the PTTH signal transduction pathway. The second messenger cAMP appears to be normally produced in response to PTTH stimulation of glands explanted from parasitized host larvae, however the downstream activation of the cAMP-dependent protein kinase does not appear to occur. In fact, a marked underphosphorylation of regulatory target proteins is observed. This underphosphorylation is associated with a significant reduction in general protein synthesis, which appears to be blocked at the translational level, to a redirection of specific protein synthesis and to a drastic suppression of ecdysteroidogenesis. These parameters appeared to be correlated in a kinetic time-course study, confirming their functional link. C. nigriceps polydnavirus (CnPDV) plays a major role in the inactivation of pupally committed host prothoracic glands, while putative factors occurring in the host haemolymph do not seem to be of particular importance at that developmental stage. Southern blot hybridization indicates the occurrence of PKI(protein kinase inhibitor)-like genes in the C. nigriceps genome, which, in contrast, are undetectable in H. virescens.