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The spontaneous activation of Aedes aegypti, and their responses to external stimuli (especially changes in temperature, humidity and carbon dioxide concentration) have been analyzed in a way that allows the controlling neural mechanisms to be inferred. In general, the flying insect turns back on leaving a favorable air stream, but does not turn on entering one. The normal attack program reduces to four basic steps: a general search initiated by a small rise in the CO2 level, no turn when the insect enters the "host stream" (i.e., the convective or other air current whose temperature and/or relative humidity has been modified by the host), an induced turn on leaving the host stream, and a visual landing. Repellents resemble CO2 in activating previously resting mosquitoes. If, however, the host stream contains a repellent vapor, the insect is made to turn on entering the host stream and is prevented from turning on leaving it. Thus the repellent vapor reverses the normal response to the host stream in two ways that are vital to success in locating a warm-blooded host. It also tends to inhibit probing. The antennal setae through which the various environmental influences are perceived can be inferred from a quantitative consideration of the responses.

The upwind guidance of flying insects was considered in a previous paper (Wright, 1958) where a homing mechanism was suggested that did not require visual contact with the ground. The response of Drosophila to attractive scents presented in various ways has now been studied. The results show that visual contact with the ground is in fact essential, and other factors of the guidance system have been clarified.

Examination of 700 northern bobwhites (Colinus virginianus), 50 each February from 1971 through 1984, from Tall Timbers Research Station, Leon County, Florida, disclosed 15 species of helminth parasites. Nine species (Raillietina cesticillus, R. colinia, Aproctella stoddardi, Cheilospirura spinosa, Cyrnea colini, Dispharynx nasuta, Heterakis isolonche, Tetrameres pattersoni, and Trichostrongylus tenuis) generally were found on an annual basis and were considered characteristic components of the helminth fauna. Infrequently found species were Brachylecithum nanum, Rhabdometra odiosa, Capillaria sp., Gongylonema ingluvicola, H. gallinarum, and Oxyspirura matogrosensis. Intensities of C. colini and H. isolonche differed among host sex and age classes, and prevalences and/or intensities of A. stoddardi, C. spinosa, T. pattersoni, and T. tenuis differed between host age classes. Prevalences and/or abundances of seven species (R. cesticillus, R. colinia, C. spinosa, C. colini, H. isolonche, T. pattersoni, and T. tenuis) varied with bobwhite density, apparently because bobwhites were either the primary or only definitive host on the area. Two species (A. stoddardi and D. nasuta) did not vary with bobwhite density, apparently due to the buffering effect of a broad range of definitive hosts on the area. Prevalences and/or intensities of R. colinia, C. spinosa, and T. tenuis differed with agricultural fields status (cultivated versus fallow) suggesting that land use and its attendant habitat changes influenced transmission of these species. The occurrence of C. spinosa and T. pattersoni in individual bobwhites was not independent and was attributed to utilization of the same species of grasshoppers as intermediate hosts. Localized tissue damage and inflammation were associated with A. stoddardi, D. nasuta, C. spinosa, C. colini and T. pattersoni. Decreases in body weight in juvenile bobwhites were associated with increasing intensities of H. isolonche and T. tenuis. The observed relationships to bobwhite density and other variables are discussed with regard to known aspects of life histories of the nine most common species.