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Does the behaviour of spruce caterpillars improve the effect of their crypticity?

Dvorackova K., Kulfan J., Zach P.

Polish Journal of Ecology

2010

Vol. 58, nr 1

145-152

Cryptic green caterpillars of Thera variata and Pungeleria capreolaria and brown caterpillars of Peribatodes secundarius, Eupithecia tantillaria and Hylaea fasciaria (Lepidoptera, Geometridae) were studied. The question was if these caterpillars could improve the effect of their crypticity by selecting for their diurnal roosting a specific place on their host plant - Norway spruce (Picea abies). We observed the preference for background type, preference for upper or undersurface, and preference for illuminated or shaded part of background. We found that the caterpillars chose special sites on their host plants. Very similar green caterpillars of T. variata and P. capreolaria roosted most frequently on the undersurface of fresh green spruce twigs (twigs with living needles). Brown caterpillars also roosted mostly on fresh twigs. P. secundarius preferred ; twig undersurface, while E. tantillaria roosted most often on the upper surface of twigs. Larvae of H. fasciaria did not prefer either the upper surface or undersurface of twigs. Comparing with the other studied species, they roosted more frequently on brown sprigs of fresh green twigs. We conclude that caterpillars could improve their mimicking of the particular parts of their host plant by the selection of their roosting position: larvae of T. variata and P. capreolaria imitate green needles, P. secundarius thin twigs, E. tantillaria dry needles captured among green needles on a living twig, and H. fasciaria thicker sprigs.

Effects of gamma-radiation on the entomopathogenic nematodes (Heterorhabditidae)

Pezowicz E.

Chemia i Inżynieria Ekologiczna

2004

Vol. 11, nr 2-3

233--237

Entomopathogenic nematodes of the Heterorhabditidae family are important pest control agents, used in biological control of several insects. Of their developmental stages, only juveniles of the third stage (J3) are free-living in goił. The development of other stages occurs in the host body. A number of abiotic factors (temperature, humidity, pesticides, and heavy metals) affect their effectiveness. Ionizing radiation seems to be an additional abiotic factor affecting some entomopathogenic nematodes. To assess the effects of gamma radiation on Heterorhabditis megidis Poinar, Jackson, Klein, the following experiments were set up: Juveniles [formula] as well as their insect hosts, larvae of the greater wax moth (Galleria mellonella) were irradiated with gamma irradiation with the following doses: 0.3, 0.5, 1.0, 1.5, 2.0, 2.5, and 3.0 kGy, and used in the following combinations: (a) irradiated insect host + irradiated nematodes; (b) irradiated insect host + non-irradiated nematodes; (e) non-irradiated insect host + irradiated nematodes; (d) non-irradiated insect host + non-irradiated nematodes (control).

Zbadano wpływ promieniowania jonizującego na nicienie entomopatogenne Heterorhabditidae. Zastosowano różne dawki promieni gamma uzyskanych z izotopu 60Co: 0,3 kGy, 0,5 kGy, 1,0 kGy, 1,5 kGy, 2,0 kGy, 2,5 kGy, 3,0 kGy. Badano: zamieranie larw inwazyjnych nicieni H. megidis pod wpływem różnych dawek promieni gamma oraz śmiertelność owadów testowych Galleria mellonella, w różnych wariantach doświadczenia. Zbadano także intensywność porażenia owadów testowych przez nicienie H. megidis. W wyniku badań stwierdzono, że niewielkie dawki promieni gamma zwiększają, a dawki promieni > 2,0, 2,5 kGy hamują patogeniczność badanych nicieni. Wszystkie badane dawki promieni gamma powodują sterylizację postaci dorosłych. Rozwój nicieni kończył się na pokoleniu form "olbrzymich".