Richard L. Lampman

Extractable hydrocarbons and kin recognition in honeybee (Apis mellifera L.)

Hydrocarbons of worker honeybees of known pedigree were extracted and analyzed using gas chromatography and mass spectrometry. Variability in hydrocarbon extracts of individual workers is determined at least in part genetically. Correlations in hydrocarbon composition of extracts were highest among more closely related individuals. Individuals maintained in groups exchange hydrocarbons but still maintain enough self-produced compounds to retain genetically determined individual characteristics. These results demonstrate that extractable hydrocarbons of bees provide sufficiently reliable genetic information to function as labels for use during kin recognition.

Problems in Estimating Mosquito Infection Rates Using Minimum Infection Rate

Determining the role of various mosquito species in the transmission of arboviruses relies on an accurate estimate of the proportion of infected individuals in an area. Basically, there are two methods for estimating the proportion of infected individuals from pooled samples. One is the widely used minimum infection rate (MIR), which is calculated as the ratio of the number of positive pools to the total number of mosquitoes tested. The underlying assumption of the MIR is that only one infected individual exists in a positive pool. This assumption is valid for arboviruses that are relatively rare, but it becomes problematic when infection rates are high and/or pool sizes are large. The other method of estimating the proportion of infected individuals in pooled samples is the maximum likelihood estimation (MLE), which is defined as the infection rate most likely observed given the testing results and an assumed probabilistic model (i.e., binomial distribution of infected individuals in a positive …

Assessment of arbovirus vector infection rates using variable size pooling.

Abstract.  Pool testing of vector samples for arboviruses is widely used in surveillance programmes. The proportion of infected mosquitoes (Diptera: Culicidae) is often estimated from the minimum infection rate (MIR), based on the assumption of only one infected mosquito per positive pool. This assumption becomes problematic when pool size is large and/or infection rate is high. By relaxing this constraint, maximum likelihood estimation (MLE) is more useful for a wide range of infection levels that may be encountered in the field. We demonstrate the difference between these two estimation approaches using West Nile virus (WNV) surveillance data from vectors collected by gravid traps in Chicago during 2002. MLE of infection rates of Culex mosquitoes was as high as 60 per 1000 at the peak of transmission in August, whereas MIR was less than 30 per 1000. More importantly, we demonstrate roles of various pooling strategies for better estimation of infection rates based on simulation studies with hypothetical mosquito samples of 18 pools. Variable size pooling (with a serial pool sizes of 5, 10, 20, 30, 40 and 50 individuals) performed consistently better than a constant size pooling of 50 individuals. We conclude that variable pool size coupled with MLE is critical for accurate estimates of mosquito infection rates in WNV epidemic seasons.

Fundamental issues in mosquito surveillance for arboviral transmission

Marked spatiotemporal variabilities in mosquito infection of arboviruses, exemplified by the transmission of West Nile virus (WNV) in America, require adaptive strategies for mosquito sampling, pool screening and data analyses. Currently there is a lack of reliable and consistent measures of risk exposure, which may compromise comparison of surveillance data. Based on quantitative reasoning, we critically examined fundamental issues regarding mosquito sampling design and estimation of transmission intensity. Two surveillance strategies were proposed, each with a distinct focus, i.e. targeted surveillance for detection of low rates of mosquito infection and extensive surveillance for evaluation of risk exposure with high levels of mosquito infection. We strongly recommend the use of indicators embodying both mosquito abundance and infection rates as measures of risk exposure. Aggregation of surveillance data over long periods of time and across broad areas obscures patterns of focal arboviral transmission. We believe that these quantitative issues, once addressed by mosquito surveillance programs, can improve the epidemiological intelligence of arbovirus transmission.

Semiochemical attractants ofDiabrotica undecimpunctata howardi barber, southern corn rootworm, andDiabrotica virgifera virgifera leconte, the western corn rootworm (Coleoptera: Chrysomelidae)

During the summers of 1984 and 1985, a variety of structurally related benzenoid compounds was evaluated in sweet corn plots as attractants for adult southern corn rootworms (SCR), western com rootworms (WCR), and northern corn rootworms (NCR). Field response to the volatiles was measured by beetle counts on baited cylindrical sticky traps placed inside the corn plots at a height of l m above ground level. SCR adults were attracted late in the season (last week of August through September, 1984 and 1985) to numerous aromatic compounds, including phenylacetaldehyde, benzyl acetone, phenethyl alcohol, phenyl acetate, indole, veratrole, methyl eugenol, methyl isoeugenol, eugenol, and isoeugenol. Although many compounds attracted SCR adults late in the season, only veratrole, phenylacetaldehyde, and chavicol were significantly active in early and middle August 1985. WCR adults were attracted to a different group of compounds, namely estragole,trans-anethole, and indole. Estragole (4-methoxy-1-allylbenzene) was an effective WCR attractant from corn tasseling in early August 1985, until the end of the trapping period in late September and early October 1985. Indole andtrans-anethole (4-methoxy-1-propenylbenzene) were less effective attractants than estragole and were most active at the beginning and/or end of the corn season. Traps baited with 100 mg of estragole caught an average of 20 times more WCR adults than unbaited control traps, and the females outnumbered the males in the baited traps. Estragole dosage tests were conducted in three sweet corn plots on different dates in 1985 and the minimum effective dose ranged between 5 and 30 mg/trap. Field tests with structural analogs revealed the importance of the site of unsaturation in the allylic side chain of estragole and the effect of different ring substituents on WCR response. The phenylpropanoids, eugenol and isoeugenol, significantly attracted NCR adults, even though these beetles were in low abundance in the test corn plots. Field tests indicate there is no cross-species response by WCR and NCR adults to their related phenylpropanoid attractants. However, in late August, SCR adults do respond to some WCR and NCR attractants (indole and several eugenol analogs). Electroantennographic analysis of SCR males revealed they can perceive peripherally a wide range of benzenoid compounds.

Effect of Temperature and Insecticide Stress on Life-History Traits of Culex restuans and Aedes albopictus (Diptera: Culicidae)

ABSTRACT The chronic effects of exposure of Culex restuans (Theobald) and Aedes albopictus (Skuse) (Diptera: Culicidae) to low concentrations of malathion were examined by exposing larvae of the two species to four malathion doses at 20, 25, and 30°C and maintaining the resulting adults at 25°C. For both species, a significant temperature by malathion interaction on survival was found. Greater temperatures at the highest malathion dosage had significantly lower survivorship than in other treatments, but this effect was not observed at 20°C. These results suggest that low temperature may buffer against some of the negative effects of malathion. For both species, temperature but not malathion had significant effects on female developmental time to adulthood and adult longevity. Temperature also affected adult female size for Ae. albopictus but not Cx. restuans. Ae. albopictus females developed faster as temperature increased, lived longer when larvae were maintained at 30°C than at 20°C, and were larger when larvae were maintained at 25°C than at 20 or 30°C. Cx. restuans females developed faster at 25 and 30°C than at 20°C and lived longer at 25°C than at 20 or 30°C. The estimated finite rate of increase (&lgr;′) for Cx. restuans was significantly lower at 20°C than at 25 and 30°C, whereas that of Ae. albopictus was significantly influenced by an interaction between temperature and malathion with significantly lower &lgr;′ at 20°C than at 25 and 30°C for all malathion treatments except 0.014 mg liter-1. Understanding how pesticides interact with abiotic environmental conditions will contribute to management decisions about vector control practices.

Culex Population Dynamics and West Nile Virus Transmission in East-Central Illinois

ABSTRACT Temporal changes in the abundance Culex restuans and Culex pipiens were monitored in east-central Illinois for over a decade using infusion-baited oviposition traps. The 2 species typically exhibited a seasonal shift in relative abundance with a mean crossover date (when the proportion of egg rafts from both species is equal) of August 10 or 11, depending on leap year, with a 95% confidence interval of ±10.7 days. The date of crossover was linearly related to the date of last spring frost and occurred on average about 123 days after the last spring frost. Despite the predictability of crossover, the weekly pattern in the proportion of Cx. pipiens before and after crossover varied considerably, even between years with similar crossover dates. After West Nile virus became established in our area, we found that transmission based on Culex from gravid traps did not increase until Cx. pipiens abundance increased in oviposition traps. Infection rates peaked within the half-month period after crossover. The peak in Cx. pipiens abundance in oviposition traps during this 3-year period was between the 2nd half of August and the end of September. A higher magnitude of transmission in 2002 coincided with warmer temperatures during July and August and an extended period in which the 2 Culex species were in relatively equal abundance.

FIRST RECORD OF AEDES JAPONICUS JAPONICUS IN ILLINOIS: DEFINING ITS SPATIAL DISTRIBUTION AND ASSOCIATED MOSQUITO SPECIES

ABSTRACT Since the initial discovery of Aedes japonicus japonicus in 1998 from sites in the northeastern United States (New York, Connecticut, and New Jersey), this invasive mosquito species now permeates local faunas throughout eastern North America and continues to expand its distribution westward. In July and August of 2006, the 1st reported specimens of Ae. japonicus were detected in east central Illinois at 2 woodlots in southern Urbana. Sampling efforts were concentrated around the site of the original detection. Dry ice–baited light traps and gravid traps caught 26,421 mosquitoes, with 5 and 6 Ae. japonicus recovered from each trap type, respectively. Although numerous larvae were found in 1 woodlot, they were restricted to a single container, a childs plastic swimming pool. Routine weekly mosquito sampling for West Nile virus (WNV) surveillance in Urbana and the adjacent city of Champaign (gravid and dry ice–baited traps placed in agricultural, industrial, residential, and urban parks) failed to detect Ae. japonicus outside of the 2 woodlots. Despite previous reports of Ae. japonicus from the adjacent states of Indiana and Missouri in 2004 and 2005, the extremely localized spatial distribution and low abundance of this species strongly suggests a recent introduction. If Ae. japonicus follows previous trends in the United States and Canada, within 1–3 years after it becomes established, its abundance, frequency of detection, and spatial distribution will significantly expand. Aedes japonicus has some characteristics of a bridge vector for West Nile virus because of its vector competency, ability to feed on mammals and birds, and potential abundance near sites of known WNV transmission in Illinois.

Olfactory responses ofOrius insidiosus (Hemiptera: Anthocoridae) to volatiles of corn silks

A synomone present in hexane extracts of corn silks was found to attractOrius insidiosus (Say). The attraction was a diurnal, innate behavior, independant of sex. A portion of the prey-searching behavior ofO. insidiosus apparently relies on olfactory perception when corn is the preys host.

Phenological changes in primary and secondary chemistry of reproductive parts in wild parsnip

Abstract Few studies have documented the developmental profile of both primary and secondary metabolites of plants; we set out to construct such a profile, in order to determine the extent to which primary and secondary metabolites covary. Primary and secondary chemistry have been documented for buds, female flowers and green fruits of wild parsnip Pastinaca sativa. A distinct qualitative shift in secondary chemistry occurs over the course of development. Mono- and sesquiterpenes were abundant in buds but absent from female flowers and green fruits. Furanocoumarins, which were found in all organs, were present at low concentration in buds, at intermediate concentrations in female flowers, and at highest concentrations in fruits. Among the primary metabolites, developmental shifts were, for the most part, quantitative. Soluble protein and fatty acid content declined with development. A qualitative change in fatty acid composition was observed in that linolenic acid inbuds was replaced by petroselinic acid in fruits. Overall variation in primary metabolites was rarely correlated with variation in secondary metabolites: of the 233 possible correlations, only 25 were significant.