Assessing Flight Potential of the Invasive Asian Longhorned Beetle (Coleoptera: Cerambycidae) With Computerized Flight Mills

Flight Mill Experiments and Computer Simulations Indicate Islands Recruit More Capable Flyers of Moths

Understanding the traits related to species colonization and invasion, is a key question for both pest management and evolution. One of the key components is flight, which has been measured for a number of insect species through radar and tethered flight mill systems, but a general understanding of insect flight at a community level is lacking. In this study, we used flight mill experiments to quantify flight abilities of moth species, and simulation experiments to study which moths in mainland China have the potential for cross-island dispersal. We found that moths from superfamily Geometroidea (family Geometridae) have the weakest flight ability among the seven Lepidoptera superfamilies, which is characterized by the shortest longest single flight (LSF), the shortest time corresponding to the longest single flight (TLSF) (timecorrespondingtothelongestsingleflight), the lowest total distance flown (TDF), and the lowest average speed during the flight (VTDF). Surprisingly, the family Pyralidae (superfamily Pyraloidea) has the highest flight endurance of all 186 species of 12 families in this study, which is unexpected, given its small size and morphological traits yet it shows the longest LSF and TLSF. The comparison between species common to mainland and islands shows that flight distance (LSF) may be more important for species spread than flight speed. The results of mainland-island simulations show that when P(LSF>CD) (the proportion of individuals whose LSF is greater than the closest distance (CD) between mainland and island to the total number of individuals in the population) is less than 0.004, it is difficult for moth species to disperse to across islands without relying on external factors such as airflow. Over extended periods, with the immigration of species with strong flight abilities, islands are more likely to recruit species with stronger flight abilities.

Effects of Starvation, Age, and Mating Status on Flight Capacity of Laboratory-Reared Brown Marmorated Stink Bug (Hemiptera: Pentatomidae)

The brown marmorated stink bug, Halyomorpha halys (Stål) (Hemiptera: Pentatomidae), is an invasive species to North America and has spread throughout most of the territory. Understanding flight in H. halys is crucial to understanding the dispersal capacity and developing forecasting models for this pest. The purpose of this research was to assess the effects of starvation, age, mating status, sex, and preflight weight on flight parameters of laboratory-reared H. halys using computer-monitored flight mills. The mean flight distance observed over a 24-h period was 266 m and the maximum distance was 7.3 km. Overall, the flight capacity of males and females was similar, even though females weighed more than males. The proportion of H. halys that initiated flight was not affected by starvation, age, or mating status. The number of bouts of individual flights and velocity significantly increased with longer durations of starvation. The number of bouts significantly decreased with increasing age. The total distance flew and total flight time was not affected by starvation, age, or mating status. Although some statistical differences were seen across the experiments, these differences likely represent minimal ecological significance. Therefore, these results suggest that H. halys are remarkably resilient, which may contribute to their success as an invasive species. The findings of this study could help better predict the dispersal potential of H. halys in Minnesota.

Quantification of the Life Time Flight Capabilities of the South American Palm Weevil, Rhynchophorus palmarum (L.) (Coleoptera: Curculionidae)

Simple Summary

The South American palm weevil, Rhynchophorus palmarum, is an invasive pest that has killed thousands of ornamental palms in San Diego County in California, USA. Emerging management plans for this pest need to consider the flight capabilities of this insect, which are not well understood. To address this shortcoming, flight mills, a type of computerized insect “merry-go round” that measures how far weevils can fly in the laboratory, were used to quantify the flight distances of 101 weevils that were flown repeatedly over the course of their lifetimes. The results indicate that weevils are strong flyers capable of flying numerous times before dying of natural causes. Over their lifetimes, weevils, on average, covered distances that cumulatively totaled >220 km. One female weevil flew an impressive cumulative distance of approximately 806 km over the course of nine consecutive flights before dying.

Abstract

The life time flight capabilities of an invasive palm pest, Rhynchophorus palmarum, were assessed using flight mill assays under controlled conditions in the laboratory. A total of 101 weevils were used for experiments and subjected to repeat flight assays. A total of 17 flight trials were run, of which the first 14 provided useful data prior to weevil death. Male and female weevils exhibited a strong capacity for repeat long distance flights. Flight metrics of interest were not affected by weevil sex or mating status. Cumulative lifetime flight distances for male and female R. palmarum averaged ~268 km and ~220 km, respectively. A maximum lifetime cumulative flight distance of ~758 km and ~806 km was recorded for one male of unknown mating status and one unmated female weevil, respectively. Dispersal data for individual flights (i.e., trials 1 through 9, 10–14 combined) and all flight trial data (i.e., flights 1–14 combined) exhibited platykurtic distributions. The results presented here may have important implications for modeling the spread of this invasive pest and for the development of monitoring and management plans.

How Far Can Rhynchophorus palmarum (Coleoptera: Curculionidae) Fly?

The palm weevil, Rhynchophorus palmarum (L.), was first recorded in San Diego County, CA in 2011 and breeding populations were recovered from infested Canary Islands date palms, Phoenix canariensis, in San Ysidro, San Diego County, in 2015. This palm pest presents a significant threat to California's edible date industry as Phoenix dactylifera is a recorded host for this weevil. The flight capabilities of R. palmarum are unknown which limits understanding of rates of natural dispersal. In response to this knowledge deficit, 24-h flight mill trials were conducted with field-collected male and female weevils. A total of 87 weevils (49 females and 38 males) were used in experiments, ~6% failed to fly >1 km in 24 h and were excluded from analyses. Of those 82 weevils flying >1 km in 24 h, the average distance flown by males and females was ~41 and ~53 km, respectively. Approximately 10% of females flew >100 km in 24 h, with two (~4%) females flying >140 km. The maximum recorded distance flown by a male weevil was 95 km. Flight activity was predominantly diurnal and flying weevils exhibited an average weight loss of ~18% while non-flying control weevils lost ~13% body weight in 24 h. The combined flight distances for male and female weevils exhibited a heavy-tailed platykurtic distribution. Flight mill data for R. palmarum are compared to similarly collected flight mill data for two other species of invasive palm weevil, Rhynchophorus ferrugineus (Olivier) and Rhynchophorus vulneratus (Panzer).

Fine-scale invasion genetics of the quarantine pest, Anoplophora glabripennis, reconstructed in single outbreaks

The xylophagous cerambycid Anoplophora glabripennis, the Asian long-horned beetle (ALB), is highly polyphagous and can colonize a wide range of broadleaved host trees causing significant economic damage. For this reason, it is considered a quarantine pest in Europe and North America. Although the global spread of ALB has been depicted recently, no comprehensive studies exist on the genetic pattern of populations' establishment and dynamics at fine-scale (i.e. within invasive outbreaks), before eradication measures are applied. This information may, however, be particularly important for an efficient management and control of invasive pests. Here, we characterized population genetic diversity and patterns of spread of ALB within and among the four outbreaks detected in Switzerland between 2011 and 2015. For this, we genotyped 223 specimens at 15 nuclear microsatellite loci and conducted specific population-based analyses. Our study shows: (1) At least three independent introductions and a, human-mediated, secondary dispersal event leading to the four outbreaks in the country; (2) An overall low intra-population genetic diversity in the viable and several years active invasive populations; (3) A colonization of single trees by homogeneous ALB genotypes; And (4) an establishment of populations several generations prior to its official discovery.

Effect of Sex and Air Temperature on the Flight Capacity of Bradysia odoriphaga (Diptera: Sciaridae)

Bradysia odoriphaga Yang & Zhang (Diptera: Sciaridae) is an important pest of Chinese chives. Information on the effects of biotic and abiotic factors on the flight performance of B. odoriphaga is crucial for understanding the pest's ability to disperse and migrate. In this study, the effects of sex and air temperature on the flight performance of B. odoriphaga imagoes were assessed by tethering individual imagoes to computerized flight mills for a 10-h experiment. The results showed that the percentage of imagoes that flew a particular distance gradually decreased as flight distance increased. The percentage of imagoes was significantly higher for males than females when the flight distance was <300 m. Sex and air temperature significantly affected average flight time (which ranged from 14.6 to 68.3 min) and average flight distance (which ranged from 10.4 to 107.2 m), but did not significantly affect average flight speed (which ranged from 3.8 to 6.4 m/min). For both females and males, the average flight distance and flight time were shortest at 18°C and longest at 22°C; the interaction between air temperature and sex was not significant. The results suggest that B. odoriphaga has a poor potential for long-distance migration. These findings will be helpful for developing forecasting and management systems for B. odoriphaga.

Impacts of Metarhizium brunneum F52 infection on the flight performance of Asian longhorned beetles, Anoplophora glabripennis

The Asian longhorned beetle (ALB), Anoplophora glabripennis, is an invasive wood-borer in North America and Europe that threatens a variety of tree genera, including Acer and Populus. All invasive ALB populations occur in quarantine zones where they are under eradication, a process that is difficult and expensive, requiring extensive surveys and host tree removals. Although ALB has been described as an insect that is typically slow to disperse, some rare individuals that fly longer distances have the potential to start infestations outside of quarantine zones. Biological control using entomopathogenic fungi has been considered as another option for managing ALB infestations. The entomopathogenic fungus Metarhizium brunneum strain F52, registered for commercial use in the United States, is effective at killing ALB adults but information is lacking on how this entomopathogen affects ALB flight behavior before death. Using quarantine-reared ALB, flight mills were used to collect data on flight performance of beetles at multiple time points after infection. Healthy (uninfected) male ALB adults always flew significantly greater distances than females. The maximum observation for total flight distance was a healthy male that flew 10.9 km in 24 hours on a flight mill. ALB adults infected with M. brunneum F52 flew significantly shorter distances compared to healthy adults, starting one week after fungal exposure. Biological control of ALB with this fungal entomopathogen could help to reduce their dispersal in the environment and, thereby, decrease the risk of adults moving outside of quarantine zones.

Factors That Influence Flight Propensity in Anoplophora glabripennis (Coleoptera: Cerambycidae)

The effects of mating status, sex, beetle age, host quality, temperature, and wind speed on the propensity of Anoplophora glabripennis (Motschulsky) (Coleoptera: Cerambycidae) to take flight were evaluated using a free flight test in the laboratory. Time to initiate flight, the angle of flight, and flight capability (when beetles were enticed to take flight) were also evaluated. Host quality, mating status, beetle age, sex, temperature, and the interactions between one or more of these were all found to be significant predictors of flight in A. glabripennis in one or more of the experiments. Female flight propensity peaked at sexual maturity and declined thereafter. Both sexes had a higher propensity to take flight from a stem section of dry host material than from a fresh one. Most (78%) males flew at least once during the four mating status/ages tested from a fresh host stem section, while only 43% of the females flew at least once after chewing an oviposition pit. Flight propensity and distance flown increased with temperature and there was no voluntary flight at 15°C. Flight propensity did not increase with wind speeds 0.0-1.0 m/s, but no ascending flight was observed at 0.5 or 1.0 m/s. Time to flight initiation did not vary with the factors evaluated. Implications these results could have on the success of eradication programs are discussed. Specifically, what factors increase the propensity of mated females to disperse, effectively expanding the infestation zone.

National Trade can Drive Range Expansion of Bark- and Wood-Boring Beetles

Several native species of bark- and wood-boring beetles (Coleoptera) have expanded their range within their native biogeographic regions in the last years, but the role of human activity in driving this phenomenon has been underinvestigated. Here we analyze 3 yr of trapping records of native bark- and wood-boring beetles (Cerambycidae and Scolytinae) collected at 12 Italian ports and their surrounding forests to help elucidate the human role in the movement of native species within their native biogeographic region. We trapped several species that occurred either inside or outside their native distributional range within Italy. Species richness and abundance of those species found in the ports located within their native range were most strongly associated with the amount of forest cover in the surrounding landscape, suggesting that they could have arrived in the ports from the nearby forests. The abundance of the species found outside their native range was instead most strongly linked to the amount of national imports arriving at the port where trapping occurred, suggesting that they were likely introduced to the ports from other parts of Italy. This study demonstrates that national sea transportation can favor species range expansion within a country, and confirms that the forests that surround ports can serve as a source of species that can be potentially moved with exports.