The Chinese pine caterpillar Dendrolimus tabulaeformis is an important destructive leaf borer in boreal coniferous forests in China. This species overwinters in the larval stage. Changes in supercooling capacity and physiological-biochemical parameters of D. tabulaeformis larvae from a natural population were evaluated at different stages during the overwintering period. Cold hardiness of overwintering larvae collected in January was significantly greater than that of larvae collected in other months. January larvae survived for 15 days at -10°C and for approximately 2 days at -15°C. By contrast, larvae collected in September survived for no more than 4 h at -5°C and those in November and March no more than 1 day at -15°C. Supercooling point gradually decreased from -5.9 ± 0.3°C in September to a minimum of -14.1 ± 1.0°C in November, then gradually increased to the original value with the advent of spring. Water content gradually decreased from September to November, remained at approximately 74.5% until March and then gradually increased to levels similar to those in September. The lipid content gradually decreased from September to November, remained stable at approximately 3.2% until March and then gradually increased to levels similar to those in September. Glycogen content increased to a peak in November and then decreased. The concentrations of several metabolites showed significant seasonal changes. The most prominent metabolite was trehalose with a seasonal maximum in November. Glucose levels were highest in January and then gradually decreased until in May they were at levels similar to those in September. Glycerol levels remained relatively stable during winter but increased significantly in May. This study indicates that D. tabulaeformis is a freeze-avoidant insect. Larvae increase their supercooling capacity by regulating physiological-biochemical parameters during overwintering., Yuying Shao, Yuqian Feng, Bin Tian, Tao Wang, Yinghao He, Shixiang Zong., and Obsahuje bibliografii
Mean development rates under cycling temperature regimes (both alternating and sinusoidal regimes) have been found to be either accelerated, decelerated or unaffected when compared to development at constant temperature regimes with equivalent means. It is generally accepted that this phenomenon is a consequence of the non-linearity inherent in the temperature-rate relationship of insect development and is known as the rate summation, or Kaufmann, effect. Some researchers invoke an additional physiological mechanism or specific adaptation to cycling temperatures resulting in a genuine alteration of development rate. Differences in development rates at constant and cycling temperatures may have important implications for degree-day (linear) population models, which are used in bath pest management and ecological studies.
Larvae of Aglais urticae L. (small tortoiseshell), Inachis io L. (peacock), Polygonia c-album L. (comma) and Vanessa atalanta L. (red admiral) (Lepidoptera: Nymphalidae) were reared at constant (10, 15, 20, 25, 30°C) and alternating (20/10, 25/15, 30/10, 30/20°C) regimes. Development rates under the alternating regimes used were found to differ from those under equivalent constant temperatures in a pattern suggestive of the Kaufmann effect: in all species development at 20/10°C was faster than at 15°C, and for three species development at 30/20°C was slower than at 25°C. The exception was A. urticae. A similar pattern was found for growth rate and pupal weight. The results are discussed with respect to cycling temperature theory and degree-day modelling., Simon R. Bryant, Jeffrey S. Bale, Chris D. Thomas, and Lit
The efficiency of Monte-Carlo procedures to test some hypotheses about the spatial patterns of larvae and damages of Lobesia botrana was studied. Two hypotheses were tested to detect spatial heterogeneity and spatial dependence. The most practical implication is to provide an efficient sampling scheme. The study of the relationship between spatial patterns and grape availability was required to explain scales of spatial heterogeneity and population dynamics studies were needed to relate it to oviposition behavior. It was tested through a third hypothesis. We adapted Monte-Carlo simulation procedures for the analysis of exhaustive count data obtained from regular grids delimited within each of two vineyards. Statistical analyses were based on count permutations and on count redistributions according to the hypotheses which were tested. Indices of aggregation and autocorrelation statistics were used. The hypotheses that we tested at different scales were random distribution of the infestations (HR), independence of vine stock (or groups of k vine stocks) infestation (HI) and independence between vine stock infestation and grape availability (HG). Monte-Carlo tests revealed the same spatial patterns for larvae and damages. We detected different spatial patterns. The implications for sampling were that sample unit could be an individual stock and that sampling along a row could not be used to estimate population density in the vineyard. Results showed that infestation of a given stock depended on grape availability on this stock and on neighboring vine stocks., Isabelle Badenhausser, Patrice Lecharpentier, Lionel Delbac, Pascale Pracros, and Lit
We investigated the effect of the feeding behaviour of young larvae of Pieris rapae crucivora Boisduval (Pieridae) on parasitism by the parasitoid wasp, Cotesia glomerata (L.) (Braconidae). Young, 1st-3rd instar larvae used approximately three sites for feeding each day. When not feeding, they moved a short distance away from the feeding sites (= feeding marks) and rested. For first, second and third instar larvae, the distances from the new mark, made within 24 h, to larva at rest were, respectively, about 3.5 mm, 5 mm and more than 10 mm. To resume feeding, they moved back to one of the former feeding sites or a new site. The percentage of the feeding marks older than 24 h that attracted parasitoids was less than 50%. Time spent searching for hosts by a parasitoid was short. Larvae placed 5 mm or more from a feeding mark were less parasitized than the larvae placed near a mark. The number of feeding marks affected parasitism. When comparing single-marked and triple-marked leaves, the percentage parasitism of the larvae on the latter was significantly lower than that of the larvae on the former. On triple-marked leaves, parasitoids visited each mark unevenly. Accordingly, the time spent searching each mark differed significantly among the marks. Because of this confusing effect, hosts are considered to be reducing the risk of parasitism. Our results demonstrate that the feeding habits of young larvae of P. rapae crucivora are adaptive in terms of reducing the risk of parasitism by C. glomerata., Aya Nakayama, Keiji Nakamura, Jun Tagawa., and Obsahuje bibliografii
From 1994-1997 the food of Coccinella septempunctata L. was investigated on the basis of gut dissections of adults and larvae collected in the field. Additionally, the gut contents of adults fed under laboratory conditions were investigated. The likelihood of recovering different prey types during gut dissection was variable, which will be illustrated by presenting some common prey fragments. The food eaten by adult C. septempunctata throughout a year was studied at a locality in Berlin-Staaken. Ladybirds were collected from March 1994 until November 1997 in different crops and habitats on roughly a monthly basis. Aphid feeding was detectable from April until October. In May and June they were the most frequent food type. Fungal spores, in most cases the conidia of Alternaria spp., became most frequent in July. Additionally non-aphid arthropods were frequently preyed upon in July. A very common non-aphid prey item were thrips. Pollen was important in May and September. Comparing the food components of newly emerged adults with those of overwintered adults some remarkable differences were detected. In newly emerged adults non-aphid arthropods and fungal spores were much more frequent than in overwintered adults whereas aphids were less frequently found. The diet of adults and larvae was also investigated in June and July in cereal fields at two other localities, Northern Flaeming and Magdeburger Boerde. No difference in adult diet was found between the three localities. The composition of the larval diet was relatively similar to that of the adults., Holger Triltsch, and Lit
PhDr. František Straňák, Zvl. otisk z Národ. hospodáře Venkova, 1916, Obsahuje přívazky : Návod k hubení hrabošů arsenovým mazem -- K otázce ochrany pšenice vůči rzi plevové -- Návod k hubení hrabošů arsenovým mazem a strychninovým ovsem / Fr. Straňák, and Converted from MODS to DC version 1.8 (EE patch 2018/05/24)