Factors Affecting the Flight Activity of <I>Winthemia Fumiferanae</I
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Factors Affecting the Flight Activity of Winthemia fumiferanae (Diptera: Tachinidae) CHRISTIAN HEBERT, CONRAD CLOUTIER, ANDJACQUES REGNIEREI Departement de Biologie, Universite Laval, Sainte-Foy, Quebec, Canada GIK 7P4 Environ.Entomol.19(2):293-302(1990) ABSTRACT The influence of variousenvironmental factors on flightactivity of Winthemia Downloaded from https://academic.oup.com/ee/article/19/2/293/468373 by guest on 01 October 2021 fumiferanae Tothill (Diptera: Tachinidae) was studied in southern Quebec from 1985 to 1987. Adults of both sexes were strictly diurnal and much more active in the presence of sunlight. Flight activity was positively related to maximum air temperature above 150Cand, to a much lesser degree, negatively related to precipitation. Males and females showed different spatial distribution patterns. Males were more numerous in the lower canopy of the forest, whereas females were more abundant in the higher canopy. Malesalsowere found more often in deciduous vegetation than on conifers, the inverse being observed for females. We conclude that sylvicultural practices that might enhance habitat diversity and natural lighting should favor the activity of W. fumiferanae as a parasitoid of the spruce budworm, Choristoneura fumiferana Clemens (Lepidoptera: Tortricidae). KEY WORDS Insecta, Winthemia fumiferanae, flight activity, environment PARASITOIDEFFICACYis determined to a large ex- gence period when males were most active and tent during adult life (Vinson 1976, Nyrop & Sim- females were maturing eggs, and during the peak mons 1986). Early during the adult stage, parasit- oviposition period of females on spruce bud worm oids select areas where host searching will be larvae (Hebert et al. 1989). We also studied the concentrated. Host density is an important factor effects of weather conditions, tree species, and influencing parasitoid adult activity (Hassell 1982), height in the canopy on activity levels. but environmental factors also are critical. In forest habitats, factors such as stand composition (Sim- mons et al. 1975), height in the canopy (Weseloh Materials and Methods 1981), and the presence of food sources (Leius 1967) The study was conducted in 1985 and 1986 in are all factors which can influence flight activity a site near Armagh, Quebec (46°46'N, 70"39'W, or levels of parasitism, or both. Parasitoid flight 270 m altitude). The environment of the plot was activity also is affected by weather conditions such diverse and dominated by a heterogeneous stand as temperature, humidity, and light (Weseloh 1976, of balsam fir (Abies balsamea (L.) Miller), white Vinson 1976). Detailed knowledge of factors af- spruce (Picea glauca (Moench) Voss), and several fecting flight activity is needed to evaluate the po- deciduous tree species including trembling aspen tential effects of sylvicultural practices on parasit- (Populus tremuloides Michaux), and white birch ism. Such understanding would help in the (Betula papyrifera Marshall). A limited amount of development of parasitoid augmentation and con- data also was obtained from two other sites, the servation strategies as part of integrated pest man- Lac Ii I'Epaule plot in the Laurentian Wildlife Re- agement programs. serve, Quebec (47°18'N, 71°12'W, 750 m altitude) Winthemia fumiferanae Tothill is a common in 1985, and the Lac Solitaire plot in the St-Maurice parasitoid attacking late instars of the spruce bud- Wildlife Reserve (47°12'N, 73°00'W, 350 m alti- worm, Choristoneura fumiferana (Clemens). It tude) in 1987. The Armagh and Lac Ii I'Epaule overwinters in a puparium within the first few plots were described in detail by Lethiecq & Re- centimeters of the forest floor under conifer trees; gniere (1988). adults emerge in late spring, and males emerge Trapping. In Armagh in 1985, two Malaise traps several days before females (Hebert et al. 1989). (Townes 1972) were operated (one at ground level, A 2-wk preoviposition period insures that mature the other at a height of 8 m above ground) in a eggs become available when spruce budworm lar- narrow abandoned forest road where parasitoid vae enter the sixth stadium, the preferred instar flight activity was likely to be higher than within for oviposition (e.H. & e.e., unpublished data). the forest (Townes 1972). A third trap, placed at Our paper reports daily patterns of W. fumi- ground level within the forest, also was operated feranae flight activity near the end of the emer- between 24 and 29 May. In 1986, two additional traps were set up in the old road at 4 and 12 m I Centrede Foresleriedes Laurenlides,C. P. 3800,1055rue above the ground (total of four traps). Traps sus- du Peps,Sainte-Foy,Quebec,CanadaG1V 4C7. pended above the ground were operated with pul- 0046-225X/90/0293-0302$02.00/0© 1990EntomologicalSocietyof America 294 ENVIRONMENTAL ENTOMOLOGY Vol. 19, no. 2 leys (Nyrop & Simmons 1986). Traps were emptied the ground. More traps also were placed in clear- daily, except for 1-2 wk at the beginning and to- ings and in an abandoned field at 1 m above the ward the end of both seasons. On three sunny days ground in grasses and shrubs. Traps were collected (7, 8, 21 June 1985), traps were inspected every 2 and replaced three times per week from early May h from 0500 to 2100 hours Eastern Summer Time to late August. Flies caught on these traps were (EST) to establish daily patterns of activity. Flies identified, sexed, and counted in the laboratory. were identified, sexed, and counted in the labo- An automatic weather station installed within ratory. W, fu.miferanae is the largest tachinid para- the Armagh study plot provided daily minimum sitoid of the spruce bud worm and is readily rec- and maximum air temperatures and precipitation ognized by its yellow scutellum and antennae. The in 1985 and 1986. males (eyes contiguous rather than separate) also Data Analysis. Mean daily times of capture of bear yellow stripes on the abdomen. adult W. fumiferanae on different trap types and White sticky traps also were used in Armagh and locations were compared with Watson-Williams Downloaded from https://academic.oup.com/ee/article/19/2/293/468373 by guest on 01 October 2021 Lac a l'Epaule in 1985. These traps, described by tests (Zar 1974). The number of flies captured on Regniere & Fletcher (1983), consisted of a pair of sticky traps exposed or not to sunlight during the cylindrical cardboard containers (trapping surface peak flight activity was compared with x2 tests. area 0.19 m2) coated with Stickem Special (Sea- Differences in total seasonal catch on different plant bright Enterprises, Emeryville, Calif,) and hung on species and habitats (yellow sticky traps, Armagh a metal coat hanger. Pairs of traps were suspended 1986) were compared by analysis of variance (AN- at 2, 4, 6, 8, 10, and 12 m above the ground on a OVA) and Duncan's multiple range test (Duncan vertical loop attached to a rope hanging between 1955, SAS Institute 1985). The seasonal trends in the tops of dominant trees; five trapping loops were the percentage of both sexes captured in conifers set up in each plot within the stand. These traps within the forest (as opposed to deciduous tree (hereinafter, intercrown traps) were inspected every species, mostly within the regeneration plot, with 2-3 d from 6 June to 6 July in f\rmagh and from the exception of trembling aspen and white birch 24 June to 31 July in Lac a l'Epaule (periods of which were common within the forest) were com- maximum flight activity of females). On three sun- pared by regression analysis. Sex ratios and vertical ny days (7, 8, and 21 June), traps were inspected distributions of catch of both sexes on conifer trees every 2 h, from 0500 to 2100 hours (EST) in Ar- were compared with x2 tests. magh to establish daily patterns of activity. On 21 The relationship between daily capture of W. June, trap pairs set up at 2 m above ground, one fumiferanae in Malaise traps and meteorological pair in each cardinal direction on two balsam fir conditions was determined with a nonlinear regres- and two white spruce trees located around a clear- sion model developed by Lavallee et al. (1988) ing, also were monitored every 2 h, Flies were which has the general form: identified, sexed, and counted in the field. To relate the flight activity of W. fumiferanae Y = g(x) f(T,P) (1) to host and nonhost tree species in various habitats more closely, yellow sticky cardboard traps (Sea- where Y is the number of flies per day, x is time bright Enterprises, Emeryville, Calif.) were used (days) after the onset of the flight season, T is max- in Armagh in 1986 and Lac Solitaire in 1987. These imum daily air temperature (0C), and P is the total traps have a rectangular trapping area (0.03 m2), daily precipitation (mm). Maximum rather than Seven such traps were attached to a rope loop run- mean daily air temperature was used because, as ning from the ground to the top of each of five will be shown later, W. fumiferanae flies by day. balsam fir and five white spruce trees, in a manner Equation 1 is based on the assumption that the such that the traps lay closely parallel to the edge daily rate of capture is a composite function of of the foliage at 0, 2, 4, 6, 8, 10, and 12 m above time and weather. The g(x) term represents the the ground, The traps were located on the south seasonal trend in fly abundance as measured with sides of the trees to receive the longest sunlight Malaise traps. This is determined by population exposure. In Armagh in 1986, additional traps were density, emergence of flies from the soil, longevity, placed at various heights in one or two trees of five and migration.