Author Institution: Associate Professor, Department of Entomology, The Ohio State UniversityHost-seeking activity of larval American dog ticks was measured by determining the proportion of unengorged larvae attached to white-footed mice, Peromyscus leucopus (Rafinesque), trapped overnight in Columbus, Ohio, in 1983. A positive linear correlation was found between larval host-seeking activity and evening ambient temperature. No similar correlation was found between this activity and insolation, relative humidity, average daily temperature, or ambient temperatures taken at other times of the day or night

Foster, Woodbridge A.

Harlan, Harold J.

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210 G. W. COLLINS II Vol. 86" The results of this investigation clearly indicate thatphotographic documentation of these paintings should bedone with isotropic illumination such as that obtainablewith a ring flash in order to eliminate the effects ofshadowing resulting from the rough rock surface. The useof reflection photometry holds considerable promise forproviding rough relative ages for those paintings partiallyobscured by calcium evaporates. In some instances,where the geological age of the evaporate can be sus-tained, it may even allow for approximate absolute ages tobe obtained. Above all, those who would interpret thepaintings of the Quetico region must accept the fact thatthey are essentially viewing examples of abstract art andshould be wary of the influences of their own personalprejudices. We have here an example of an Indian Picto-graph which virtually satisfies all of the Miller (1955)criteria for a supernova-lunar conjunction representation,but which is most likely not such a picture.ACKNOWLEDGEMENTS. The author acknowledges the assistance ofDr. William Ploughe and the other four individuals who accompaniedhim on the trip to Ahsin Bay. Without their help the journey wouldnot have been possible. Additional thanks are due the U.S. ForestService and Quetico Provincial Park Ranger Jon Nelson for assistancein the safe removal of the injured members of the party. We are alsoindebted to Shirley Peruniak of the Quetico Provincial Park Staff forvaluable insights into the Park and for her knowledge of the IndianPictographs of the region.LITERATURE CITEDBrandt, J. C. and R. A. Williamson 1979 The 1054 Supernovaand Native American rock art. Archaeoastronomy, J. Hist. Ast.Supp. 1,10: sl-s38.Collins, G. W., II 1985a A possible representation of the Super-nova of 1054 A.D. Bull. Amer. Ast. Soc. No. 18: 41.1985b Picture. Ast. Mag. (May) 13: 60.Dewdney, S. and K. E. Kidd 1967 Indian Rock Paintings of theGreat Lakes. Univ. of Toronto Press, p. 26.Mayer, D. 1979 Miller's hypothesis: some California and Nevadaevidence. Archaeoastronomy, J. Hist. Ast. Supp 1, 10: s51-s74.Miller, W. C. 1955 Two prehistoric drawings of possible astro-nomical significance. Ast. Soc. Pac, Leaflet 314.Temperature Effects On Host-Seeking By Larval American Dog Ticks, Dermacentorvariabilis (Say)1'2Harold J. Harlan, LTC, MS3 and Woodbridge A. Foster, Associate Professor, Department of Entomology, The Ohio State University, Columbus,OH 43210ABSTRACT. Host-seeking activity of larval American dog ticks was measured by determining the proportionof unengorged larvae attached to white-footed mice, Peromyscus leucopus (Rafinesque), trapped overnight inColumbus, Ohio, in 1983. A positive linear correlation was found between larval host-seeking activity andevening ambient temperature. No similar correlation was found between this activity and insolation, relativehumidity, average daily temperature, or ambient temperatures taken at other times of the day or night.OHIO J. SCI. 86 (5): 210-212, 1986INTRODUCTIONTemperature has been reported to influence stronglythe activity of immature American dog ticks, Dermacentorvariabilis (Say), and other tick species (Smith et al. 1946,Hall and McKiel 1961, Lees 1969, Balashov 1972,Dukes and Rodriguez 1976, Rechav 1979). Conversely,Atwood and Sonenshine (1967) reported that air tem-perature was not related to the host-seeking of immatureD. variabilis in field studies in Virginia. They reportedthat average daily solar radiation (insolation) receivedat ground level was the dominant meteorologic factorcorrelated with host-seeking by immature forms of thisspecies.Observations reported here on larval D. variabilis host-seeking activity, as reflected by the proportion (percent)Manuscript received 21 January 1986 and in revised form 29September 1986 (#86-5).Opinions expressed in this article are those of the authors and donot reflect any official position of the Department of Defense.'Present address: USAEHA, FSA-North, Ft. Meade, MD20755-5225.of host-attached larvae that were visibly unengorged,were part of a larger study on the ecology of RockyMountain Spotted Fever in Ohio. Absolute numbers ofunengorged larvae and average numbers per host were notused to measure activity because the numbers andlocations of small mammal traps employed varied greatlyon different days, owing to limited availability of trapsand investigator's time. Fewer traps will catch lowernumbers of animals from which fewer ticks could pre-sumably be collected. Tick density also would be ex-pected to vary with trap site (Smith et al. 1946).Percentages of unengorged larvae were considered tobe a reliable indicator of recent host-seeking activity bythese larvae, because the period between attachment andvisible blood engorgement is relatively short (<48 h),and because the host collection date and time were accu-rately known for all specimens.METHODS AND MATERIALSWhite-footed mice, Peromyscus leucopus (Rafinesque), were caughtalive in Sherman-type traps with peanut butter and corn chips as bait.Traps were set in the late afternoon or early evening and emptiedbetween 0700 and 1200 h the next morning on 21 different days.Ohio J. Science TEMPERATURE EFFECTS ON HOST-SEEKING 211This study was conducted in the American Addition, which is an area(2 km X 3 km) of scattered houses dispersed among untended lots,fields, and woods within northeastern Columbus, Ohio.Numbers of larval D. variabilis collected and the numbers visiblyunengorged were recorded for each white-footed mouse taken in thestudy area in 1983- The percentage of unengorged larvae was com-pared to published National Oceanic and Atmospheric Adminis-tration (NOAA) weather data from the Port Columbus Airportlocated 6.3 km nearly due east of the study area. Engorgement, asused herein, means ingestion of a substantial amount of food (i.e., tothe point of visible detection) and not necessarily absolute reple-tion. Attention was focused on ambient temperature and insolation(sunshine) data for the trapping period (March-May, 1983).The raw data for each collection date were combined for eachsuccessive 3°C interval of temperature through the observed range of5°-23°C. The proportion of larvae unengorged (i.e., numberunengorged/total number collected) was calculated for each of thesetemperature intervals, and the resulting percentage was plottedagainst the median temperature value for each of the respective inter-vals. Temperatures used were those recorded by the NOAA weatherstation at 1900 h (EST) on the evening previous to any given larvalcollection date. A general linear model of the relationship betweentemperature and the percent of unengorged larvae collected was runwith the Statistical Analysis System (Ray 1982).RESULTSTemperature apparently influenced the proportion ofunengorged larvae of D. variabilis that were collectedfrom P. leucopus taken in the study area from March-May,1983. There was a positive correlation between the per-cent of larvae unengorged and the ambient temperaturesrecorded at 1900 h (Table 1). For example, collectionsfrom 16 March, 1 April, and 16 May yielded among thesmallest proportions (58.7, 53.8 and 56.1%, respec-tively) of unengorged larval D. variabilis coupled withambient temperatures of less than 10°C at 1900 h oneach of the respective previous evenings. The col-lections from 17 March and 2 April were representativeof the opposite example. Both yeilded notably higherpercentages (85.7 and 90.7%, respectively) of un-engorged larvae coupled with ambient temperaturesabove 10°C at 1900 h on each of the two respectiveprevious evenings.Ambient temperature showed a positive linearrelationship to the percentages of larval D. variabilis thatwere unengorged, when data were combined within 3°Cintervals (Table 1) and plotted against the median valueof each respective temperature interval (Fig. 1). A gen-eral linear model of these data indicated a fairly stronglinear relationship, with a coefficient of determination(r2) of 0.82 and P(r > F) = 0.01 for this model.TABLE 1Proportions of unengorged Larval D. variabilis compared to NO A A*temperature data from the previous evening. Collections weregrouped by 3 °C intervals.Temp. Median No. larvae unengorged/ %range (°C) temp. (°C) No. of larvae collected Unengorged5-88-1111-1414-1717-2020-236.59.512.515.518.521.5236/35662/96267/37562/83205/275423/55966.364.671.274.774.575.77 6 -7 5 -7 4 -7 3 -Q7 2 -111O71 -DCO7 0 -oz6 9 -111z6 8 -13zLJJo6 5 -DC11164 -Q.6362/ // /, - - ////////// / '/ f"NOAA = National Oceanic and Atmospheric Administration.5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22TEMPERATUREFIGURE 1. Computer-generated plot of percentage of larval D. vari-abilis collected unengorged from P. leucopus vs. ambient tem-perature (°C) at 1900 h the previous evening. Dotted lines show 95%confidence limits.Identical treatment of data for insolation showedalmost no correlation with the percentages of unengorgedD. variabilis larvae collected from the white-footed mice.The NOAA data for average daily temperatures, for rela-tive humidity, and for temperatures taken at other timesof day showed only very weak correlations with thesesame percentages of unengorged larvae.DISCUSSIONThe choice of the 1900 h NOAA readings used in thisstudy was based upon the primary food-seeking activityperiod (dusk to 2200 h) reported for P. leucopus (Amin1974, Falls 1968, Mineauand Madison 1977). Live trapswere most likely entered by mice during their normalforaging period, and the chance of contacting larval tickswas probably minimal after they entered the traps. Trapentry and its timing, therefore, probably constituted acut-off of further increase in the numerical tick burden ofany given mouse.Larval D. variabilis require 3-5 days to fully engorge(Smith et al. 1946, Atwood and Sonenshine 1967). How-ever, the vast majority of larval D. variabilis (i.e. Fi larvaehatched from the eggs of field-collected adults) fed onwhite rats in our laboratory showed visible distentionwith blood within 36 to 48 h after placement on a host.This time was relatively independent of ambient tem-perature because the larvae were placed in direct contactwith the hosts. Based on these observations, any larvaetaken from field-collected hosts and not yet engorgedmust have been picked up by their host no more than36 h earlier. The live traps were emptied each morning,so that each mouse was restricted from exposure to larvalticks for less than 24 h. Any larvae picked up the pre-vious evening (i.e. just before their host's capture, sincePERCENT UNENGORGED212 H.J. HARLAN Vol. 86these mice are most active in late evening) could not havebecome visibly engorged by the time the host was pro-cessed the next morning. These larvae would have beenrecorded as "unengorged". On the other hand, larvaepicked up more than 24 h earlier, and very likely at least36 to 48 h earlier (i.e. during the peak activity period ofthe host two evenings previous to the morning the hostwas processed), would almost certainly have become vis-ibly engorged.Accepting the above, it follows that, when relativeproportions of unengorged larvae increased noticeably,relative rates of host-seeking activity by larval D. vari-abilis in the study area must have increased similarly. Onsome days few hosts were collected, or few larval ticks perhost were found, resulting in small samples that weresubject to sampling error in the proportions of larvaeunengorged. Also, a few larger samples deviated widelyfrom expected values, but are probably explained byrapid weather changes recorded the previous afternoonscausing subsequent substantial decreases or increases inthe temperatures recorded by NO A A at 1900 h. Changesin actual microclimates where larval ticks sought hostsmay have preceded or lagged behind these recordedchanges. Any such distortions were minimized by pool-ing the data into successive 3°C temperature intervals.These data support the premise that there was an effectof temperature on larval D. variabilis host-seeking activ-ity in the area and time period examined in the presentstudy. The best explanation for these observations is thatan increase in the ambient evening temperature led toincreased host-seeking activity by the larval ticks. Theseobservations also suggest that, at least for larval D. vari-abilis in Columbus, Ohio, insolation should be rejectedand evening temperature accepted as the main deter-minant of host-seeking activity.LITERATURE CITEDAmin, O. M. 1974 Distribution and ecological observations ofwild mammals in southeastern Wisconsin. Wise. Acad. Sci., Artsand Letters, 62: 311-326.Atwood, E. L. and D. E. Sonenshine 1967 Activity of the Ameri-can dog tick, Dermacentor variabilis (Acarina: Ixodidae) in relationto solar energy changes. Ann. Entomol. Soc. Am., 60(2): 354-362.Balashov, Y. S. 1972 Bloodsucking ticks (Ixodoidea)-Vectors ofdiseases of man and animals. Misc. Publ., Entomol. Soc. Am.,8(5): 161-376.Dukes, J .C. and J.G. Rodriguez 1976 A bioassay for host-seeking responses of tick nymphs (Ixodidae). J. Kans. Entomol.Soc. 49(4): 562-566.Falls, J.B. 1968 Activity, pp. 543-570. In: J. A. King [ed.],Biology of Peromyscus (Rodentia). Am. Soc. Mammal., Spec. Publ.No. 2.Hall, R. R. andj. A. McKiel 1961 Occurrence of the Americandog tick, Dermacentor variabilis (Say), in Western Nova Scotia. Can.Entomol., 93: 891-893.Lees, A. D. 1969 The behaviour and physiology of ticks. Acar-ologia, 11(3): 397-410.Mineau, P. and D. Madison 1977 Radio-tracking of Peromyscusleucopus. Can. J. Zool., 55: 465-468.Ray, A. A. 1982 [ed.] Statistical Analysis System Users Guide.1982 Edition. SAS Institute, Inc., Cary, NC. 584 pp.Rechav, Y. 1979 Migration and dispersal patterns of three Africanticks (Acari: Ixodidae) under field conditions. J. Med. Entomol.,16(2): 150-163.Smith, C. N., M. M. Cole, and H. K. Gouck 1946 Biology andcontrol of the American dog tick. USDA Tech. Bull. No. 905.74 pp.

Temperature Effects on Host-Seeking by Larval American Dog Ticks, Dermacentor variabilis (Say)

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Temperature Effects on Host-Seeking by Larval American Dog Ticks, Dermacentor variabilis (Say)

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