ABSTRACT
Little work has been done to quantify the number of eggs oviposited by blow flies (Diptera: Calliphoridae) in studies examining colonization behavior. Egg counting methods currently available are time-consuming and destructive. This study used ImageJ software and analysis of covariance to relate the volume of egg masses to the number of eggs laid by three different blow fly species: Lucilia sericata (Meigen), Phormia regina (Meigen), and Chrysomya rufifacies (Macquart). Egg mass volume, species, and the interaction of species and egg mass volume all affected the number of blow fly eggs deposited in egg masses. Both species identity and egg mass volume are important when predicting egg number, as such a single regression equation cannot be used to estimate egg number for these three species. Therefore, simple linear regression equations were determined for each species. The volume of individual eggs was incorporated into the model, yet differences between species were observed, suggesting that the orientation of the eggs oviposited by multiple conspecific females within egg masses influences egg estimates. Based on our results, we expect that imaging software can be used for other blow fly species, as well as other insect species; however, equations specific to each species must be developed. This study describes an important tool for quantifying egg deposition in a nondestructive manner, which is important in studying the colonization behavior and life history of insects of ecological and forensic importance.
Subject(s)
Clutch Size/physiology , Diptera/physiology , Embryo, Nonmammalian/physiology , Photography/methods , Animals , Female , Linear Models , OvipositionABSTRACT
Sitona lineatus L. (Coleoptera: Curculionidae) is an invasive pest in North America and its geographical range is currently expanding across the Canadian prairies. Adults and larvae of S. lineatus feed upon the foliage and root nodules, respectively, of field pea, Pisum sativum L. (Fabales: Fabaceae), and may contribute to economic losses when population densities are high. Integrated pest management (IPM) programs that incorporate economic thresholds should be used to manage S. lineatus populations in a sustainable manner. The impact of nitrogen fertilizer on field pea yield and the relationships between adult weevil density and above- and below-ground damage and yield were investigated in southern Alberta, Canada using exclusion cages on field pea plots. In each cage, 32 field pea plants were exposed to weevil densities ranging from zero to one adult weevil per plant. Nitrogen-fertilized plants yielded 16% more than unfertilized plants. Nitrogen-fertilized plants had fewer root nodules than unfertilized plants, but fertilizer had no effect on foliar feeding by S. lineatus. Adult density affected foliar feeding damage, with increases in above-ground damage associated with increases in S. lineatus density. Adult density did not affect root nodule damage, larval density, foliar biomass or seed weight. Overall, these results indicate that terminal leaf damage may be used to estimate adult weevil density but cannot be used to predict larval density or yield loss. Further research is required to better understand the impact of larval damage on yield and determine if economic thresholds can be developed using data from large-scale production systems.
