Dawn H. Gouge

Parasitism of Subterranean Termites (Isoptera: Rhinotermitidae: Termitidae) by Entomopathogenic Nematodes (Rhabditida: Steinernematidae; Heterorhabditidae)

In laboratory bioassays, Steinernema riobrave Cabanillas, Poinar and Raulston (355 strain), Steinernema carpocapsae (Weiser) (Mexican 33 strain), Steinernemafeltiae (Filipjev) (UK76 strain), and Heterorhabditis bacteriophora Poinar (HP88 strain) were all capable of infecting and killing three termite species, Heterotermes aureus (Snyder), Gnathamitermes perplexus (Banks), and Reticulitermes flavipes (Kollar) in laboratory sand assays. S. riobrave and S. feltiae caused low levels of Reticulitermes virginicus (Banks) mortality under the same conditions. At 22 degrees C, significant mortality (> or = 80%) of worker H. aureus and G. perplexus was caused by S. riobrave, in sand assays, indicating the need for further study. Because of the short assay time (3 d maximum), reproduction of the nematodes in the target host species was not recorded. All nematode species were observed to develop to fourth-stage juveniles, preadult stages, or adults in all termite species with the exception of R. virginicus. Only S. riobrave developed in R. virginicus. Nematode concentration and incubation time had significant effects on the mortality of worker H. aureus. S. riobrave consistently generated the highest infection levels and mortality of H. aureus in sand assays.

The susceptibility of different species of sciarid flies to entomopathogenic nematodes

Steinernema feltiae is the most effective nematode for controlling sciarid species but S. carpocapsae does exert some control. S. feltiae is less effective at 30 degrees C than at 22 degrees C. S. anomali, S. riobravis and two Heterorhabditis spp. gave better control at the higher temperature. All six sciarid species tested were susceptible to S. feltiae but there was some variation in the level of infection. UK isolates of S. feltiae were more effective against UK sciarids than the nematode isolates from other European countries which were tested. Adult sciarids are infected by S. feltiae and can disperse nematodes to nematode-free compost.

Phylogeographic structure of cotton pest Adelphocoris suturalis (Hemiptera: Miridae): strong subdivision in China inferred from mtDNA and rDNA ITS markers

Phylogeographic patterns of some extant plant and vertebrate species have been well studied; however, they are poorly understood in the majority of insects. The study documents analysis of mitochondrial (COI, CYTB and ND5) and nuclear (5.8S rDNA, ITS2 and 28S rDNA) data from 419 individuals of Adelphocoris suturalis, which is one of the main cotton pests found in the 31 locations in China and Japan involved in the study. Results show that the species is highly differentiated between populations from central China and peripheral China regions. Analysis of molecular variance showed a high level of geographical differentiation at different hierarchical levels. Isolation-by-distance test showed no significant correlation between genetic distance and geographical distance among A. suturalis populations, which suggested gene flow is not restricted by distance. In seven peripheral populations, the high levels of genetic differentiation and the small Nem values implied that geographic barriers were more likely restrict gene flow. Neutrality tests and the Bayesian skyline plot suggested population expansion likely happened during the cooling transition between Last Interglacial and Last Glacial Maximum. All lines of evidence suggest that physical barriers, Pleistocene climatic oscillations and geographical heterogeneity have affected the population structure and distribution of this insect in China.

Activity Trends and Movement Distances in the Arizona Bark Scorpion (Scorpiones: Buthidae)

ABSTRACT The bark scorpion, Centruroides sculpturatus Ewing, is a nocturnal, cryptic, nonburrowing, mobile species that is common in urban landscapes spanning the desert southwest. Bark scorpions are often found in dense localized populations in cities, but the question of whether this is because the species is metabolically movement limited or choose to aggregate has not been addressed. Field observations lead us to believe that the scorpions move very little. Their ability to move is tested here. A circular pacing ring was constructed to observe the distance individuals could move in 2 h under both dark and light conditions. Observations under light motivate the arthropods to move, and significantly greater distances were observed in light trials, the maximum travel distance being 104.37 m, while the maximum distance in dark trials was 14.63 m. To monitor movement in the field, telemetry tags were used to mark female and male scorpions over 21 d during which relocation distances were recorded daily. Additionally, 12-h and 6-h overnight observational periods took place during which, scorpion movements were recorded hourly. Overall, it was found that scorpions moved significantly more in the pacing ring than in the field, indicating that field individuals are not moving at their maximum potential. Movement limitation does not explain their distribution pattern. In both the pacing ring and field, gender and pregnancy status had significant influence on distances moved. We conclude that C. sculpturatus is capable of much greater movement than is typically observed in the field.

Exploration of Refuge Preference in the Arizona Bark Scorpion (Scorpiones: Buthidae)

ABSTRACT The ongoing difficulty in understanding how Centruroides sculpturatus (Ewing) uses the built environment has prompted this study in exploring refuge choices in a school environment and in laboratory behavioral assays. Radio telemetry tags were used at an urban site heavily populated with C. sculpturatus to track scorpions for a period of 21 d from 1 to 21 August 2013. Complimentary laboratory work tested scorpions in refuge choice arenas targeting variables of four crevice widths—14.0, 9.3, 7.0, and 4.6 mm—or of a vertical versus horizontal orientation preference. These crevice sizes were picked as a response to crevices being naturally used in the field. Telemetry and observations tallied significant preference for artificial structural harborage. Ninety-five percent of the structure refuge use occurred in hollow block walls. Vegetative harborage, debris, and underground burrows were not selected with any significance compared with each other or structures. Generalized additive models (GAMs) indicated the strongest predictive power from individual preference. The behavioral choice assays yielded a significant preference for the largest of crevice widths offered, 14.0 mm and to a lesser extent 9.3 mm, both horizontally and vertically. GAMs for these assays indicated size as the strongest predictive factor in choices. The orientation tests and GAMs showed individual preference driving choice favoring vertical planes. Observations about negative geotaxis in assay and refuge use details from the field are also reported.

Flight Capacity of Sitophilus zeamais Motschulsky1 in Relation to Gender and Temperature

Abstract. The maize weevil, Sitophilus zeamais Motschulsky, is a major insect pest of stored grain worldwide. We evaluated flight of maize weevils by using a 26-channel computer-monitored flight-mill system to estimate total flight distance, total flight duration, and mean flight velocity at different temperatures. Temperature but not gender influenced propensity of maize weevils to fly. Flight distances and durations varied, but warm temperatures (34°C) diminished the ability of female maize weevils to fly. Despite apparent temperature-based patterns in flight parameters of males, effects of temperature on male flight ability were not statistically demonstrated. The effect of temperature on flight velocity was similar for both genders and indicated greater flight velocity at 28°C than at 22 or 31°C. Knowledge of differences in flight capacity between genders and among temperatures provides insights to consider for management of this major insect pest of stored grain.