Leon G. Higley

Forensic Entomology: An Introduction

Dorothy E. Gennard. Forensic Entomology: An IntroductionJohn Wiley and Sons, Chichester, United Kingdom, 2007224 pp.,

Effects of temperature on development of Phormia regina (Diptera: Calliphoridae) and use of developmental data in determining time intervals in forensic entomology.

55.00 (soft), ISBN: 978-0-470-01479-0 As forensic entomologists, we constantly hear claims that student interest in forensic science is a passing fad. However, a close inspection of past and future needs soon shows that the demand for more and better qualified forensic scientists has been strong and continues to grow. In much the same way, readers sometimes make a cursory scan of a book and dismiss it as light weight or superficial. We made that mistake with Forensic Entomology: An Introduction —we didn’t expect the book to amount to much, but the more we read, the more we found to value. As we have learned yet again, whereas you can judge a blow fly by its puparium, you can’t judge a booklouse by its exoskeleton. Forensic Entomology: An Introduction is not a reference or a manual; it is an introductory undergraduate text. Actually, it could even serve as a supplemental text in some graduate courses …

Trap color and placement affects estimates of insect family-level abundance and diversity in a Nebraska salt marsh

Abstract Precise developmental data for forensic indicator blow fly species are essential for accuracy in the estimate of the post-mortem interval (PMI). Why, then, does the determination of the PMI result in conflicting time frames when published conspecific developmental data are used? To answer this question, we conducted constant temperature trials between the developmental minimum temperature and upper threshold temperatures (8–32°C) on the forensically important blow fly species Phormia regina (Meigen) (Diptera: Calliphoridae). Flies were reared using two designs to quantify sources of variation. We measured rearing container temperatures and internal growth chamber temperatures by using thermocouples to accurately record temperatures experienced by larvae and to construct a degree-day model. Differences in experimental design, as seen across temperature studies for this fly species, did not significantly impact larval development. We also found that using set chamber temperatures rather than rearing container temperatures altered the final degree-day model. Using any minimum threshold (including an empirically determined true minimum) other than that from linear interpolation (x-intercept) violated degree-day assumptions and invalidated estimates of the PMI. We observed the minimum developmental temperature to be higher (14°C) than that generated under the x-intercept method (5.46°C) by using data from oviposition to adult emergence. This difference along with the noted difference in accumulated degree-days (using different base temperatures) suggests a need for additional experimentation on other forensically important fly species at low temperature thresholds to help with development of curvilinear models. Former and current estimates of the PMI may be inaccurate if the process to determine the time frame ignored degree-day model assumptions or was based upon questionable data sets.

Dispersal of Adult European Corn Borer (Lepidoptera: Crambidae) Within and Proximal to Irrigated and Non-irrigated Corn

Sampling programs to establish baseline ecosystem information (e.g., species abundance and diversity) often fail to consider the potential influence of sampling techniques on results. Research on sampling economically important insects has demonstrated the possible influences of trap color and trap placement on results, but few data have been collected from natural environments. Consequently, we examined the effects of color (yellow and blue) and placement (exposed and shaded by plants) of sticky traps on insect captures and diversity estimates from a Nebraska inland salt marsh community. We identified 1913 specimens from 67 insect families collected during five trapping dates in July 1996. More Cicindelidae were collected on exposed traps, and more Staphylinidae, Dolichopodidae, Cicadellidae, and Thripidae were collected on shaded traps. More Dolichopodidae were collected on yellow traps, while more Syrphidae and Thripidae were collected on blue. Shannon and alpha diversity measures were significantly higher for shaded traps than exposed traps, but were not affected by trap color. Our results highlight the importance of characterizing sampling techniques when establishing diversity estimates. These data provide the first complete accounting of community‐level insect response to colored sticky traps and provide new information for color preference of non‐economic insect species.

Maggot development during morgue storage and its effect on estimating the post-mortem interval.

Abstract The European corn borer, Ostrinia nubilalis (Hübner), causes economic damage to corn, Zea mays L., throughout the Corn Belt. Because this insect has become the primary target of Bacillus thuringiensis Berliner (Bt) transgenic corn, current efforts addressing the management of O. nubilalis resistance to Bt corn require information on adult European corn borer dispersal and factors affecting its dispersal. In 1998 we conducted mark-release-recapture, release-recapture, and caged-mating studies to directly measure and compare local dispersal patterns of O. nubilalis adults within and proximal to irrigated and non-irrigated cornfields. Releases of marked adults were made corresponding to the first and second flight of O. nubilalis in eastern Nebraska. Adult dispersal was significantly different between irrigated and non-irrigated cornfields. Released adults tended to remain in and near irrigated cornfields, but dispersed out of and away from non-irrigated cornfields. When released at the edge of the cornfield, neither male nor unmated female O. nubilalis displayed an initial tendency to move out of irrigated corn and into the mixed smooth bromegrass (Bromus inermis Leyss) and broadleaf-weed field edge. Mating efficiency in a late-season cornfield was not significantly different than in dense foxtail (Setaria spp.). Generally, we found that adult O. nubilalis dispersal may vary depending on variables such as action-site availability and agronomic practices and their interaction with O. nubilalis life history.

Population Dynamics of Soybean Aphid and Biotic Mortality at the Edge of Its Range

ABSTRACT: When insect evidence is obtained during autopsy, forensic entomologists make decisions regarding the effects of low‐temperature (−1°C to 4°C) storage of the body and associated insects when estimating the post‐mortem interval (PMI). To determine the effects of storage in a morgue cooler on the temperature of maggot masses, temperatures inside and outside of body bags containing a human cadaver and porcine cadavers (seven replicates) were measured during storage. Temperatures remained significantly higher (p<0.05) inside of the body bags relative to the cooler, and remained at levels sufficient for maggot feeding and development. If the assumption that no insect development takes place during preautopsy refrigeration is made, potential error rates in PMI estimation of 8.6–12.8% occur. The potential for blow fly larvae to undergo significant development while being stored in the morgue is a possibility that forensic entomologists should consider during an investigation involving samples collected from autopsy. Case and experimental evidence also demonstrate that substantial tissue loss can occur from maggot feeding during morgue storage.

Distribution, Ecology and Population Dynamics of the American Burying Beetle [Nicrophorus Americanus Olivier (Coleoptera, Silphidae)] in South-central Nebraska, USA

Abstract The soybean aphid, Aphis glycines Matsumura, was introduced to north central North America from Asia in 2000, and it has become a major pest of soybean, Glycine max (L.) Merr. Understanding how natural enemies impact aphid populations in the field is an important component in developing a comprehensive management plan. We examined the impact of naturally occurring predators in the field by using exclusion cages during July–August 2004 and 2005. Field cages of different mesh diameters were used to exclude different sizes of natural enemies from aphid-infested plots. Plots were surveyed twice weekly for A. glycines and natural enemies. Densities were recorded. Cage effects on mean temperature and soybean growth were found to be insignificant. Significant differences in aphid density were found between treatments in both years of the study (2004 and 2005); however, aphid densities between years were highly variable. Orius insidiosus (Say) was the most commonly occurring predator in the field. Other natural enemies were present in both years but not in high numbers. Parasitoids were present in both years, but their numbers did not suppress aphid densities. Treatment differences within years were related to the abundance of natural enemies. The large differences in aphid abundance between years were associated with the higher number of O. insidiosus found in the field in 2005 (416 total O. insidiosus) than in 2004 (149 total O. insidiosus). This study suggests that naturally occurring predators, primarily O. insidiosus, can have a large impact on A. glycines populations when predator populations are established before initial A. glycines colonization.

Survival of Immersion and Anoxia by Larval Tiger Beetles, Cicindela togata

The endangered American burying beetle, Nicrophorus americanus Olivier, was previously widespread throughout eastern North America. In the past century numbers of this beetle have drastically declined and currently remnant populations are known from only six states despite intensive surveying efforts conducted for the last nine years. Efforts aimed at discovering and managing remnant populations have been generally limited by a lack of knowledge concerning N. americanus biology. We used baited pitfall traps to define the range of the Gothenburg, Nebraska population of N. americanus. Using mark-recapture techniques, we estimate that the annual Gothenburg population consists of more than one thousand individuals, meeting the recovery plan criterion to become the third breeding population in the Midwest region. Beyond estimates of population size and range, we present novel data on seasonal and daily activity, sex ratio, age-grading and foraging distances. In 1995 and 1996, the Nebraska population was univoltine and female biased, with over-wintering mature beetles emerging in early June and teneral beetles emerging in August. Nocturnal activity was highest in the third and fourth hours following sunset but was not strongly correlated with temperature. During foraging, beetles travel up to six kilometers, but the majority of our recaptures occurred at distances of less than 0.5 km, suggesting that distances between traps be increased to ensure independence of sampling units. This information will allow future work on captive breeding, re-introduction and genetic studies.

New Understandings of Soybean Defoliation and their Implication for Pest Management

Abstract The sedentary terrestrial larvae of the tiger beetle, Cicindela togata, inhabit areas that are often flooded for days or weeks. We tested the ability of these larvae to survive immersion and anoxia. Maximum survival time of immersed, anoxic C. togata was 6 days at 25 C. Time to 50% mortality (LT50) in these conditions was 85.9 ± 23.5 h. Survival times were more than eight times longer than those of similarly treated larvae of Tenebrio molitor (LT50 10.1 ± 3.2 h). Similar or somewhat longer survival times were observed in larvae of C. togata exposed to an anoxic nitrogen atmosphere (LT50 102 ± 31 h) and of T. molitor (LT5014.4 ± 6.5 h). At 10 C, LT50 of C. togata in anoxic atmospheres exceeded 10 days. Tiger beetle larvae are physiologically capable of surviving several days of inundation during floods without mechanisms to prevent burrow flooding. By entering a quiescent state, C. togata larvae survive much longer periods of anoxia than has been previously reported for terrestrial insect larvae.

Economic injury level concepts and their use in sustaining environmental quality

Uncertainties regarding the relationships between insect defoliation and yield loss limit existing management programs. Consequently, experiments were conducted over four years in multiple locations to better characterize soybean responses to defoliating insects. Results indicate that soybean yield reductions from insect defoliation primarily result from reduced light interception of defoliated plant canopies. Changes in leaf senescence were associated with defoliation and were identified as a compensatory mechanism. These results offer the potential for more accurate pest management guidelines and new approaches to managing defoliation through the development of defoliation-tolerant soybean varieties.