Submitted to: Journal of Medical Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/3/2002
Publication Date: 5/1/2002
Citation: Dowell, F.E., Broce, A.B., Wirtz, R.A., Xie, F., Fabrick, J., Throne, J.E., Baker, J.E. 2002. Chronological age-grading of flies by near-infrared spectroscopy. Journal of Medical Entomology. 39(3): 499-508. Interpretive Summary: Age structures of an insect population have a significant impact on its rate of growth, behavior of its individuals, and effectiveness of control programs. For disease-carrying insects such as flies and mosquitoes, the age structure of a population can affect the epidemiology of transmitted diseases. Previous chronological age determination methods include examining wings, measuring cuticle thickness, and measuring pterin accumulations. A rapid, simple method of chronological age-grading that has the potential to be applied in field situations and that could provide accurate information on the age structure of an insect population could have a significant impact on pest management decisions. This research reports the potential of near infrared (NIR) spectroscopy to determine the chronological age of individual flies. Results showed that young and old individual insects could readily be differentiated based on their NIR absorption spectra. The procedures developed in this research are simpler and faster than other existing methods. This technology can have an impact on population analysis of insects of both agricultural and medical- veterinary importance.
Technical Abstract: Near-infrared spectroscopy (NIRS) was used to determine the chronological age of house flies, Musca domestica (L.), stable flies, Stomoxys calcitrans (L.), and face flies, Musca autumnalis De Geer. Young and old age groups could readily be differentiated based on their NIR absorption spectra. Results were similar to those achieved by measuring pterin levels in fly heads. Accuracy of age classification rates were similar when analyzing NIR spectra obtained from whole flies, fresh heads, dried heads, or ethanol preserved heads. Differences in absorption spectra were observable at NIR wavelengths common to CH functional groups. This NIRS procedure is simpler and faster than measuring pterins and can be used to age-grade ethanol-preserved heads. This research could help scientists study disease outbreaks and determine the effectiveness of control programs.