Impact of Embryonopsis halticella eaton larvae (Lepidoptera: Yponomeutidae) feeding in Marion Island tussock grassland

Summary Embryonopsis halticella is a brachypterous moth endemic to the Kerguelen Province of sub-Antarctic islands. Its larvae are strictly host-specific grass-borers of the tussock grass Poa cookii, and are the major herbivores on Marion Island. Monthly sampling over one year (1984) on Marion Island showed that E. halticella larvae reach a biomass of 0.222 g m^-2 (dry mass) in P. cookii grassland in summer. In feeding experiments conducted in the laboratory on Marion Island, larvae consumed 0.3 X their own live mass in leaf material daily. Extrapolated consumption rates in the field range from 1 kg ha^-1 month^-1 in winter to 18 kg ha^-1 month^-1 (dry mass) in summer. Total annual consumption, based on leaf feeding only, amounts to 86 kg ha^-1 (dry mass). Significant shifts in diet from foliage to seeds occur during spring, and larvae also consume their own frass and exuviae. It is calculated that E. halticella larvae remove 2.5% of the annual production of Poa cookii in Marion Island tussock grassland.     

Inertia in physiological traits: Embryonopsis halticella caterpillars (Yponomeutidae) across the Antarctic Polar Frontal Zone

Geographic variation is characteristic of many physiological traits at the population and species levels. However, several recent studies have suggested that population-level variation is either limited or that it is mostly a consequence of phenotypic plasticity. Here we show that there is considerable physiological inertia in cold hardiness, upper thermal tolerance limits and desiccation resistance in caterpillars of the sub-Antarctic moth Embryonopsis halticella Eaton, such that populations from two climatically different islands are physiologically very similar. Both populations are moderately chill tolerant, with no difference in the supercooling points of caterpillars (-17 to -20 degrees C). Within their host plants caterpillars of both populations freeze at substantially higher, and statistically equivalent temperatures (-9.5 to -11.5 degrees C). The populations also have similar upper lethal limits (38 degrees C), and survival times of dry conditions (6-170 h depending on mass). The previously inexplicably low freezing point of caterpillars at the climatically less severe Marion Island seems likely a consequence of physiological inertia given that the freezing point of caterpillars within their hosts is only a few degrees below absolute minima at the older, and colder, Heard Island. Lack of adaptive geographic variation in physiological traits has consequences for models of range limits, and highlights the importance of exploring phenotypic plasticity as a response to climatic variation.     

Interactions between plant odours and pheromone reception in small ermine moths (Lepidoptera: Yponomeutidae)

Interactions between plant odours and pheromone reception werestudied in small ermine moths (Yponomeuta spp.) with electroantennogramand single cell recordings, both separately and simultaneously.The results verified that interactions do indeed occur at thereceptor level. It is suggested that, in the reproductive isolationof these moths, plant odours may play both a direct role throughplant odour receptors and an indirect role via modulation ofpheromone receptors.     

Critical thermal limits,temperature tolerance and water balance of a sub-Antarctic caterpillar,Pringleophaga marioni (Lepidoptera: Tineidae)

Thermal tolerance, supercooling point, water balance and osmoregulatory ability of Pringleophaga marioni Viette (Lepidoptera: Tineidae) are investigated in this study. Field-fresh larvae had a mean CT(Min) (cold stupor) of -0.6 degrees C and a mean CT(Max) (heat coma) of 38.7 degrees C. The mean supercooling point of field-fresh individuals was -5.0 degrees C. Caterpillars showed 100% survival of freezing to -6.5 degrees C, but at -12 degrees C mortality rose to 100%. Survival of a 30h exposure to -6.0 degrees C was 80%, but declined to 30% in the 6-12h interval at -7.5 degrees C. No caterpillars survived for longer than 12h at -9.0 degrees C. Survival of high temperatures (35 degrees C and above) was poor. Tolerance of water loss (46% of fresh mass) and rates of water loss (1% fresh massh(-1)) were similar to those found in other mesic insects. P. marioni larvae were incapable of metabolizing lipids to replenish lost water and showed no haemolymph osmoregulatory ability. It is suggested that the preponderance of freeze tolerance in high-latitude southern hemisphere species may be associated with their occurrence in moist habitats, and that the "freeze tolerance" category be re-examined in the light of the range of strategies adopted by such arthropods.     

In vitro Metabolism of Flupyrazofos to Plutella xylostella (Lepidoptera: Yponomeutidae) and Spodoptera exigua (Lepidoptera: Noctuidae)

In vitro metabolism study was conducted to observe the role of enzymes and its kind responsible for tolerance in metabolism of flupyrazofos to Diamond backmoth (DBM), Plutella xylostella as a susceptible insect and Beet armyworm (BAW), Spodoptera exigua as a tolerance insect. The results indicated that there were some differences between the DBM (LD₅₀, 0.54 ppm) and BAW (LD₅₀, >2,000 ppm). In the microsomal fractions, the 4th instar BAW larvae metabolized almost the same amount (about 38%) of flupyrazofos with or without NADPH, but it increased the amount of flupyrazol in the 3rd instar larvae of DBM. Flupyrazofos-oxon was slightly increased with the addition of NADPH in both species. With the addition of piperonyl butoxide (PB) or Iprobenfos (IBP), the amount of flupyrazol was decreased to one third of flupyrazol produced by NADPH in BAW and one fourth of flupyrazol produced by NADPH in DBM. Some effects of inhibitors, PB and IBP, and co-factor, NADPH, were showed when flupyrazofos was metabolized with or without them. This means that esterase and oxidase are responsible for the tolerance mechanism of flupyrazofos in DBM and BAW.     

A correlation between macronutrient balancing and insect host-plant range: evidence from the specialist caterpillar Spodoptera exempta (Walker)

In an earlier study, we showed that the ingestive responses of the generalist caterpillar Spodoptera littoralis to foods imbalanced in their protein:carbohydrate content is similar to generalist locusts, but differs from that of specialist-feeding locusts. Here we further pursued the comparison by repeating the experiments using a closely related specialist caterpillar, Spodoptera exempta. First, caterpillars were allowed to self-compose a diet of preferred protein:carbohydrate balance by mixing between nutritionally complementary foods. Then, they were confined to one of five imbalanced foods, in which we measured the trade-off between over- and under-ingesting the two nutrients. On complementary foods, the caterpillars actively regulated their protein and carbohydrate intake. In the no-choice experiment, those fed excess-protein foods ingested small surpluses of protein compared with generalist feeders, thus showing a pattern of nutrient balancing similar to that observed in specialist locusts. Utilisation data indicated that ingested excesses and deficits were to some extent offset by differential utilisation. Evidence also showed that post-ingestive responses of the specialist S. exempta were less flexible than those observed in the generalist S. littoralis, a pattern which is again in accordance with comparisons of acridids differing in their host-plant range.     

Genetic differentiation among various populations of the diamondback moth, Plutella xylostella (Lepidoptera: Yponomeutidae)

Genetic variation among 14 populations of Plutella xylostella (Linnaeus) from USA (Geneva, New York), Brazil (Brasilia), Japan (Okayama), The Philippines (Caragan de Oyo), Uzbekistan (Tashkent), France (Montpellier), Benin (Cotonou), South Africa (Johannesburg), Réunion Island (Montvert), and five localities in Australia (Adelaide, Brisbane, Mareeba, Melbourne, Sydney) were assessed by analysis of allozyme frequencies at seven polymorphic loci. Most of the populations were not in Hardy-Weinberg equilibrium and had a deficit in heterozygotes. The global differentiation among populations was estimated by the fixation index (Fst) at 0.103 for the 14 populations and at 0.047 when populations from Australia and Japan, which differed most and had a strong genetic structure, were excluded from the analysis. By contrast, the populations from Benin (West Africa) and Brazil (South America) were very similar to each other. Genetic differentiation among the populations was not correlated with geographical distance.     

Biochemical Characterization of C-type Lectin in the Diamondback Moth,Plutella xylostella (Yponomeutidae: Lepidoptera)

Lectins due to their affinity to carbohydrate moiety are involved in diverse functions like cell attachment in embryogenesis, organogenesis and cellular trafficking as well as nonself recognition in immune responses. Agglutinating activity was detectable in Plutella xylostella (Yponomeutidae: Lepidoptera) against 14 different species including bacterial and yeast cells, among which the whole body homogenate of P. xylostella agglutinated Providencia vermicola, Flavobacterium sp., and Saccharomyces cerevisiae with high titers. On analysis of physico-chemical properties, this putative agglutinating factor (s) was specifically dependent on the presence of Ca⁺⁺ for its activity and was reversibly sensitive to EDTA. The agglutinating activity was stable at pH 6–8, but was heat-labile. The agglutinating factor (s) was proteinaceous in nature as it was completely precipitable by ammonium sulphate. Its carbohydrate binding activity was demonstrated by inhibition assay, which revealed that methyl α-D-mannopyranoside inhibited agglutination against P. vermicola. In contrast, P. xylostella parasitized by an endoparasitoid wasp, Cotesia plutellae (Braconidae: Hymenoptera), also showed the agglutination properties with somewhat higher activity than the nonparasitized. Carbohydrate inhibition assay with methyl α-D-mannopyranoside was detectable at one-fold higher concentration in the homogenate of the parasitized larvae, suggesting that the agglutinating factor (s) is inducible or due to de novo parasitism-specific synthesis. These results suggest the presence of calcium-dependent lectin in P. xylostella and an alteration in the agglutinating property by C. plutellae parasitization.     

Taxonomic review of the genus Thecobathra (Lepidoptera,Yponomeutidae) from Taiwan

The Taiwanese species of Thecobathra are reviewed. Four new species of Thecobathra: T. heppneri n. sp., T. minuta n. sp., T. pauciguttata n. sp., and T. taiwanensis n. sp. are described. The female genitalia of T. basilobata are described for the first time. Keys to all the Taiwanese species of Thecobathra are provided.     

Interactions between Chromolaena odorata (Asteraceae) and Pareuchaetes pseudoinsulata (Lepidoptera: Arctiidae)

Feeding of Pareuchaetes pseudoinsulata caterpillars caused the leaves of Chromolaena odorata to turn yellow. Leaf yellowing could not be induced either by artificial removal of leaves or by drenching the plant with a solution of excreta from P. pseudoinsulata caterpillars. Yellow leaves appeared tougher but had the same energy level as that of green leaves. The amount of nitrate-nitrogen was significantly higher in yellow leaves than green leaves. P. pseudoinsulata caterpillars prefer to feed on green leaves. When forced to feed on yellow leaves, they exhibit slow growth and high mortality. Defensive factors in plants attacked by insects seemed to prevent further infestation of plants. In the field, caterpillars on the yellow plants were found during both day and night whereas on green plants they appeared to feed at night and hide in the ground at daytime.     

New host-plant records for the defoliator Ormiscodes amphimone (Fabricius) (Lepidoptera: Saturniidae)

Ormiscodes amphimone (Fabricius) is a phytophagous moth species known to severely defoliate woody species in Chile and Argentina. Here we document new records of O. amphimonehost associations emphasizing the role of Nothofagus pumilio as its primary host in our study area. This new record for Argentina is highly significant given the economic importance of N. pumilio as a timber resource and the potential of O. amphimone to generate extensive outbreaks.     

裸腹小白巢蛾雌性记述(英文)

The female of Thecobathra partinuda Fan,Jin et Li,2008 is described for the first time,with illustration of the genitalia.A comparison is made between the females of this species and T.kappa(Moriuti,1963).     

Rapid responses to high temperature and desiccation but not to low temperature in the freeze tolerant sub-Antarctic caterpillar Pringleophaga marioni (Lepidoptera,Tineidae)

A broad definition of rapid cold hardening (RCH) is that it is the process whereby insects increase their survival of a sub-zero temperature after a brief (h) pre-exposure to a less severe low temperature. The effects of various pre-treatments on survival of two h at -7.9 degrees C were investigated in the freeze tolerant sub-Antarctic caterpillar Pringleophaga marioni (Lepidoptera: Tineidae), the first time RCH has been investigated in a freeze tolerant arthropod. All caterpillars froze when exposed to -7.9 degrees C, and none of the low temperature pre-treatments (-5, 0, 5 and 15 degrees C, as well as -5 degrees C and 0 degrees C with a delay before freezing) nor slow cooling (0.1 degrees C/min) elicited any improvement in survival of -7.9 degrees C as compared to controls. However, high temperature treatments (25, 30 and 35 degrees C), desiccation and acclimation for 5 days at 0 degrees C did result in significant increases in survival of the test temperature, possibly as a result of heat shock protein production. Haemolymph osmolality was elevated only by the 35 degrees C pre-treatment. It is suggested that the unpredictable environment of Marion Island means that P. marioni must always be physiologically prepared to survive cold snaps, and that this year-round cold hardiness therefore supersedes a rapid cold hardening response.     

Sublethal effects of hexaflumuron on development and reproduction of the diamondback moth,Plutella xylostella (Lepidoptera: Yponomeutidae)

Abstract Effects of hexaflumuron at 10% lethal concentration (LC₁₀) and LC₂₅ on development and reproduction parameters of the diamondback moth, Plutella xylostella (Linnaeus, 1753) (Lep.: Yponomeutidae) were investigated. Estimated LC₅₀, LC₁₀ and LC₂₅ values of leaf dip bioassay of hexaflumuron on the third instar larvae of the P. xylostella were 1.48, 0.59 and 0.91 mg/L, respectively. Hexaflumuron decreased pupal weight in the parent generation at sublethal concentrations but in the offspring generation, this effect was not observed. Sublethal concentrations increased egg, first and second larval instar and pupa developmental time and shortened life span of adults, but did not change the third and fourth larval instars and pre‐pupa developmental period. Also fecundity of females reduced significantly but hatchability of treatments and control were similar. Survival rate of pre‐adult stages declined significantly at LC₂₅ concentration. Reproduction parameters such as reproductive rate (R₀) and intrinsic rate of increase in sublethal concentrations were significantly lower compared with control, but gross reproduction rate (GRR) at the LC₁₀ concentration was increased and it could be hormoligosis. Also hexaflumuron significantly increased doubling time (Dt). We conclude that the sublethal effects of hexaflumuron might exhibit significant effects on the population dynamics of P. xylostella.     

Molecular Phylogeny of the Small Ermine Moth Genus Yponomeuta (Lepidoptera,Yponomeutidae) in the Palaearctic

Background

The small ermine moth genus Yponomeuta (Lepidoptera, Yponomeutidae) contains 76 species that are specialist feeders on hosts from Celastraceae, Rosaceae, Salicaceae, and several other plant families. The genus is a model for studies in the evolution of phytophagous insects and their host-plant associations. Here, we reconstruct the phylogeny to provide a solid framework for these studies, and to obtain insight into the history of host-plant use and the biogeography of the genus.

Methodology/Principal Findings

DNA sequences from an internal transcribed spacer region (ITS-1) and from the 16S rDNA (16S) and cytochrome oxidase (COII) mitochondrial genes were collected from 20–23 (depending on gene) species and two outgroup taxa to reconstruct the phylogeny of the Palaearctic members of this genus. Sequences were analysed using three different phylogenetic methods (parsimony, likelihood, and Bayesian inference).

Conclusions/Significance

Roughly the same patterns are retrieved irrespective of the method used, and they are similar among the three genes. Monophyly is well supported for a clade consisting of the Japanese (but not the Dutch) population of Yponomeuta sedellus and Y. yanagawanus, a Y. kanaiellus–polystictus clade, and a Rosaceae-feeding, western Palaearctic clade (Y. cagnagellus–irrorellus clade). Within these clades, relationships are less well supported, and the patterns between the different gene trees are not so similar. The position of the remaining taxa is also variable among the gene trees and rather weakly supported. The phylogenetic information was used to elucidate patterns of biogeography and resource use. In the Palaearctic, the genus most likely originated in the Far East, feeding on Celastraceae, dispersing to the West concomitant with a shift to Rosaceae and further to Salicaceae. The association of Y. cagnagellus with Euonymus europaeus (Celastraceae), however, is a reversal. The only oligophagous species, Y. padellus, belongs to the derived western Palaearctic clade, evidence that specialisation is reversible.     

Interactions between Fusarium species from sugarcane and the stalk borer, Eldana saccharina (Lepidoptera: Pyralidae)

In this study, beneficial relationships between Fusarium species in sugarcane and the stalk borer, Eldana saccharina (Lepidoptera: Pyralidae) were demonstrated in vitro . In addition, Fusarium species with antagonistic properties were found to inhabit sugarcane. Attenuated Fusarium isolates from sugarcane stalks collected across the South African sugar industry were incorporated into diet formulated to mass rear E. saccharina . Of the over 200 Fusarium isolates obtained, 10 that significantly improved the survival and development of E. saccharina larvae and considered to be beneficial were selected for further study, as were 10 that were detrimental or antagonistic to the stalk borer. Twelve of the selected isolates were identified as F. sacchari by direct sequencing of translation elongation factor-1α fragments, eight of which resulted in reduced numbers of surviving larvae and significantly lower larval masses. F. proliferatum isolates resulted in increased survival and mass of E. saccharina and three of the five isolates assigned to the F. pseudonygamai group enhanced E. saccharina development. Results from olfactory choice experiments suggested the production of attractive and repellent metabolites by certain isolates. Findings from this study may offer additional or alternative strategies for managing E. saccharina infestation of sugarcane.     

Photoperiodism and seasonality in neotropical population of Plutella xylostella L. (Lepidoptera: Yponomeutidae)

Neotropical populations of the diamondback moth Plutella xylostella L. have seasonal cycles of growth and decrease, and moth migration plays a fundamental role in generating such population dynamics. Since the oscillation of these populations is predictable, photoperiod might operate as a signal that triggers the migratory behaviour of the insect. Migration in insects is usually preceded by reproductive diapause, a photoperiodic response that can be characterised by morphological, physiological and behavioural alterations that permit to discriminate between migratory and non-migratory forms. In this study, I tested whether the pre-imaginal and reproductive development of P. xylostella from Minas Gerais (Brazil) is affected by artificial day-lengths that are equivalent to the periods of natural population growth or decrease. No evidence of photoperiodic response was found for the insect reared in laboratory on five different constant photoperiods, from 8h to 16h of light per day. There was no significant variation in survival and duration of egg, larva, and pupa stages or in pupal weight, adult size (forewing length), fecundity, and longevity. Although some species have geographically distinct photoperiodic responses, previous assumptions that cosmopolitan P. xylostella responds to photoperiod in temperate regions was questioned. Migratory and population seasonality among neotropical populations of P. xylostella certainly occurs independently of the photoperiodic announcement of seasonal changes in habitat quality.     

Sequestration and metabolism of host-plant flavonoids by the Pale Grass Blue, Pseudozizeeria maha (Lepidoptera: Lycaenidae)

Flavonoids in the eggs, larvae, pupae and adult butterflies of Pseudozizeeria maha were identified and quantified. Isovitexin (apigenin 6- C -glucoside) was the dominant flavonoid detected in pupae and imagines, whereas saponarin (isovitexin 7- O -glucoside) was the dominant flavonoid in larvae. Saponarin, biotransformed from isovitexin by the larvae, was found to be reconverted into isovitexin at the pupal stages. The total amounts of accumulated flavonoids differed between sexes, particularly in adults where the bodies of females had a much higher flavonoid concentration than that of the males. These flavonoids were also detected in the eggs. These results indicate the possibility that flavonoids are utilized in not only wing coloration but also as a chemical defense compound against natural threats.