Nemorilla pyste Walker 1849

Nemorilla pyste (Walker, 1849), Fig. 47 Host records ex. Choristoneura fumiferana: Tothill 1913, as Exorista pyste ex. Tortrix fumiferana (QC); Richmond 1941b, as Nemorilla [= N. maculosa] ex. Cacoecia fumiferana on spruce (SK, MB, ON); Daviault 1946, as Nemorilla maculosa ex. Archips fumiferana (QC); Dowden et al. 1951, as Nemorilla floralis ex. Archips fumiferana (NY); Raizenne 1952 (ON); McGugan & Blais 1959 (ON); Schaffner 1959, as Nemorilla floralis (northeastern United States); Blais 1960 (QC); Blais 1965 (QC); Huber et al. 1996 (NB). Host records ex. Choristoneura fumiferana and/or Choristoneura occidentalis: Brown 1941, as Nemorilla maculosa ex. Cacoecia fumiferana (Canada); † Dowden et al. 1948, as Nemorilla floralis ex. Archips fumiferana (North America); † Zwolfer 1961, as Nemorilla maculosa ex. C. fumiferana (North America); † Arnaud 1978, ex. C. fumiferana (BC, OR, SK, MB, ON, QC, NY). Host records ex. Choristoneura fumiferana, Choristoneura occidentalis and/or Choristoneura pinus: † Ross 1952, ex. spruce and/or jack pine budworm (Canada). Host records ex. Choristoneura occidentalis: McKnight 1974 (CO). Host records probably ex. Choristoneura occidentalis: Bedard 1938, as Nemorilla floralis ex. Cacoecia fumiferana on Douglas fir (“northern Rocky Mountain region”); Wilkes et al. 1949, ex. C. fumiferana (BC); Carolin & Coulter 1959, as Nemorilla floralis ex. C. fumiferana (OR); † Coppel 1960, ex. C. fumiferana (BC). Host records ex. Choristoneura parallela: Franklin 1943, as Nemorilla floralis ex. Cacoecia parallela (MA); † Arnaud 1978 (MA); † Huber et al. 1996 (America north of Mexico). Host records ex. Choristoneura pinus: Richmond 1938, as “Hemorilla” maculosa ex. spruce budworm, Cacoecia fumiferana, on jack pine (MB, ON); Richmond 1940, as Nemorilla maculosa ex. jack pine budworm, Cacoecia fumiferana, on jack pine (SK, MB, ON); Richmond 1941a, as Nemorilla maculosa ex. jack pine budworm, Archips fumiferana, on jack pine (SK); Dixon & Benjamin 1963, as Nemorilla floralis (WI); † Arnaud 1978 (WI); † Huber et al. 1996 (America north of Mexico). Host records ex. Choristoneura rosaceana: Davis 1912, as Exorista pyste ex. Archips rosaceana (IL); Schaffner 1959, as Nemorilla floralis ex. Archips rosaceana (northeastern United States); † Arnaud 1978 (IL, northeastern United States); † Huber et al. 1996 (America north of Mexico). Host records ex. Choristoneura rosaceana and/or Pandemis limitata: Pfannenstiel & Unruh 2003 (WA); Cossentine et al. 2004 (BC). Nemorilla pyste is a common species that is widespread throughout Canada, the United States, and Mexico (O’Hara & Wood 2004). It is a dark coloured tachinid, generally 4.0– 7.5mm long, with three black stripes on the thorax (median stripe quite broad) and a mottled abdomen. It was included in a key to the puparia of dipterous parasitoids of Choristoneura species by Ross (1952) and in a key to the adults of dipterous parasitoids of C. occidentalis (as C. fumiferana) in British Columbia by Coppel (1960). The mode of oviposition has not been described for Nemorilla pyste, but is probably similar to that in other members of the tribe Winthemiini (including Hemisturmia parva and Smidtia fumiferanae of the species treated here). The female uses a telescopic ovipositor to attach eggs to the body of a host. The eggs hatch after several days and the first instar immediately burrows into the host. Nemorilla pyste attacks late instar larvae of Choristoneura species and emerges from the pupa (Davis 1912; Dowden et al. 1948; Carolin & Coulter 1959; McKnight 1974). It is likely, based on specimens of N. pyste in the Canadian National Collection of Insects reared from various hosts, that the tachinid either pupariates in the host pupa or emerges as a mature maggot and pupariates elsewhere. The parasitoid has two or more generations per year and overwinters as a larva in various hosts (Schaffner 1959). Nemorilla pyste has been reported frequently as a parasitoid of Choristoneura species, but the level of parasitism was generally very low (Dixon & Benjamin 1963; Dowden et al. 1951; Carolin & Coulter 1959; McGugan & Blais 1959; Blais 1960; McKnight 1974). It was not ranked among the top 15 hymenopterous and dipterous parasitoids of C. occidentalis (as C. fumiferana) in British Columbia in a study by Wilkes et al. (1949), nor included among the parasitoids of spruce budworm in Maine by Tilles and Woodley (1984). However, during outbreaks of C. pinus in Saskatchewan in 1939 and 1940, N. pyste (as N. maculosa) was considered one of the most important parasitoids of the budworm (Richmond 1940; Richmond 1941a). Nemorilla pyste has a broad host range. It is recorded from about 30 species in each of the Pyralidae and Tortricidae and has one to several hosts in each of the Gelechiidae, Glyphipterygidae, Hesperiidae, Lycaenidae, Lymantriidae, Noctuidae, Oecophoridae, and Yponomeutidae (Arnaud 1978).

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