Early responses of bark and wood boring beetles to an outbreak of the hemlock looper Lambdina fiscellaria (Guenée) (Lepidoptera: Geometridae) in a boreal balsam fir forest of North America

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The biology of the phonotactic parasitoid, Homotrixa sp. (Diptera: Tachinidae), and its impact on the survival of male Sciarasaga quadrata (Orthoptera: Tettigoniidae) in the field

Abstract.

• 1 Unlike most parasitoids, tachinid flies of the tribe Ormiini use sound to locate their hosts. Although thought to exert selection pressure on their host's calling behaviour, little is known about the biology of ormiines. Accordingly, this study reports the biology and impact of the ormiine Hornotrixa sp. upon calling males of the univoltine bushcricket Sciarasaga quadrata Rentz in south-western Australia.
• 2 Populations of adult S.quadrata were monitored in the field over two successive calling seasons. Females, which do not call, were not parasitized by Hornotrixa sp., but the risk of parasitism for males increased as the 3-month calling season progressed. Parasitism did not commence until c. 2 weeks into the calling season, but by the end of the season up to 87% of surviving males were parasitized.
• 3 Parasitized males lived for 14 days and were found singing until their penultimate evening before death in the field. Unparasitized males lived on average 69 days and a maximum of 119 days.
• 4 Multiparasitism of hosts was common, with up to sixteen fly larvae found within parasitized males. The number of fly larvae within hosts significantly increased at the end of the season. However, successful emergence of fly larvae from hosts, as well as pupal size, significantly decreased as more than one fly larva developed within the host.
• 5 Hornotrixa sp. has a long pupal duration of 30–31 days at 20°C. As a consequence, only one complete fly generation, which overwinters in the pupal stage, is likely within each host generation.
• 6 No evidence for differential (size-bias) mortality by Hornotrixa sp. on male S.quadrata was found. The size of parasitized and unparasitized males collected in the field was not significantly different.
• 7 It is concluded that Hornotrixa sp. is a significant mortality factor acting on the survival of adult male S.quadrata.

     

Effects of root nodules and taproots on survival and abundance of Sitona hispidulus (Coleoptera: Curculionidae) on Medicago sativa

ABSTRACT.

• 1 The effects of food resources on populations of larvae of Sitona hispidulus (F.), a root and nodule herbivore of Medicago sativa L., were investigated in 1983 and 1984.
• 2 Density-dependent mortality among first-instar larvae indicated that a lack of available root nodules, the primary resource for first instars, contributed to the 66.2±5.2% and 80.7±4.1% mortalities of first-instar larvae in 1983 and 1984, respectively. Initial densities of larvae entering the soil were 31.7±2.4 and 15.6±1.3 per soil sample (10.5 cm diam. ×15 cm deep) in 1983 and 1984, respectively (±SEM).
• 3 Survivorship and number of first-instar larvae per soil core sample were significantly related to number and biomass of nodules per soil sample. Percentage soil moisture was not consistently correlated with survivorship and number of larvae per soil sample.
• 4 Numbers of second- and third-instar larvae were not consistently correlated with either nodule or taproot biomass.
• 5 Numbers of fourth-instar larvae were associated with taproot biomass, suggesting that taproot surface area may also limit population levels of S.hispidulus. No correlations were found between taproot and nodule biomass on any sampling date indicating that high numbers of fourth-instar larvae associated with larger taproots were not merely due to a greater survival of first instars associated with larger taproots.
• 6 The study suggests that population levels of nodule-herbivores are controlled by the availability of root nodules. A sparse distribution of nodules results in high levels of mortality among nodule-herbivores of Medicago sativa.

     

Emergence of adult female Sirex nigricornis F. and Sirex noctilio F. (Hymenoptera: Siricidae) coincides with a decrease in daily minimum and maximum temperature

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A population study in Jamaica on adult Sceliphron assimile (Dahlbom) (Hymenoptera: Sphecidae)

Abstract.

• 1 A mark–recapture study on the sphecid wasp Sceliphron assimile (Dahlbohm), analysed by Jolly's stochastic method (1965), was made from 3 December 1974 to 22 February 1975 at Green Bay, St Catherine, Jamaica.
• 2 Population levels in an 18.2 ha study area fluctuated about a mean of 281 for males, 259 for total females and 87 for reproducing females, while the probable carrying-capacity for these reproductives was about 104.
• 3 Mean estimated daily survival rates were 0.903 for males, 0.924 for total females and 0.945 for reproducing females. For the first two categories these rates decreased (p < 0.02) during the study, probably reflecting increasing emigration. Reproducing females probably do not emigrate and their survival did not significantly decrease.
• 4 Minimum age was linearly related to wing wear (r=+0.69, P < 0.001) and the latter associated with the progressive maturation and ageing of the ovaries. All surviving females become parous by middle age.
• 5 The mean rate of fecundity in the field was dependent on female age and was reduced during prolonged drought. Curves of total achieved fecundity appropriate to realistic survival rates give 4.2–16.8 eggs/female. The Jamaican mean was 9.6 ± 2.3 and that for Green Bay 8.6.
• 6 The proportion of females in the Green Bay population was 0.48 ± 0.03 while 0.55 was expected at emergence.
• 7 A cyclic budget is used to estimate immigration and emigration, and these were important causes of population change.
• 8 For Jamaica, only an estimated 28% of females survived to nest.

     

Insecticidal activities of some medicinal plants against Sitophilus zeamais (Motschulsky) (Coleoptera: Curculionidae) on stored maize

A study was carried out to evaluate the insecticidal activity of Zanthoxylum zanthoxyloides, Aristolochia ringens, Garcinia kola, Morinda lucida, Euphorbia hirta, Croton zambesicus, Colocasia esculenta, Ficus exasperata and Tetrapleura tetraptera on Sitophilus zeamais at ambient temperature of 28?±?2?°C and 70?±?5% relative humidity. The plants powder was applied at 5, 10 and 20% (wt/wt) of maize grain. Weevil mortality, adult emergence, percentage damage, percentage reduction and weevil perforation index were observed. The result obtained showed that only the powder of Z. zanthoxyloides and A. ringens effect mortality on the weevil as they both achieved more than 50% weevil mortality within 96?h of application. However, powder of Z. zanthoxyloides had the highest mortality effect on the weevil as it achieved 100% within 72?h at 5%(wt/wt) and its effect was significantly (p?<?0.05) different from other powders. Also, powder of Z. zanthoxyloides, A. ringens and M. lucida showed a reduction capacity on the emergence of the adult weevil at 20%(wt/wt). Moreover, Z. zanthoxyloides prevented the emergence of the adult weevil even at 5%(wt/wt) but effect was not significantly different from A. ringens and M. lucida at 20%(wt/wt) as they both achieved 0% and 0.67% adult emergence. The powders also reduced the damage of the treated seeds. Z. zanthoxyloides prevented the damage of the seeds at 5, 10 and 20%(wt/wt) while A. ringens prevented the seed damage at 20%(wt/wt). However, effect of all the powders increased with increase in the powder concentration.     

Winter survival of Ceramica pisi (Lepidoptera: Noctuidae) in Iceland

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Arthropod predation limits the population density of an herbivorous lady beetle,Henosepilachna niponica (Lewis)

1. The possible impact of arthropod predation on inter-population variation in adult density of a thistle-feeding lady beetle, Henosepilachna niponica (Lewis ) was evaluated by means of predator exclusion experiments conducted in the field.
2. The population density of newly-emerged adults at one habitat in the upstream area (site F) was significantly lower than at another in the downstream area (site A) although the egg density was nearly identical in the two habitats.
3. In the habitat with lower adult density, egg mortality was higher due to higher levels of predation. A predator exclusion experiment demonstrated that arthropod predation was the main factor causing high mortality during the immature stages, and physical factors such as heavy rains were unlikely to influence larval survivals.
4. Earwigs, ground beetles, predaceous stink bugs, and spiders were identified as the main predators in the study area. Of these, an earwig, Anechura harmandi (Burr ) was more predominant than other predators and was significantly more abundant in the habitat with low adult densities.

     

Insecticidal efficacy of some plant powders and extracts against the Angoumois grain moth,Sitotroga cerealella (Olivier) (Lepidoptera: Gelechiidae)

Powder and extract from four plants were evaluated for their insecticidal efficacy against the Angoumois grain moth, Sitotroga cerealella (Olivier) in the laboratory at a temperature of 28 ± 2°C and a relative humidity of 75 ± 5%. The plants included Aristolochia ringens L., Khaya ivorensis (K.), Strophanthus hispidus (D.C.) and Zanthoxylum zanthoxyloides Lam. The powder was applied at the rate of 0.2, 0.4 and 0.6 g/20 g of paddy rice, while the extract was applied at the rate of 1%, 2% and 3%/20 g of paddy rice. Parameters evaluated were adult moth mortality, adult emergence and weight loss in treated paddy after infestation. Results shows that adult moth mortality increased as concentration of powder increased. Significant differences (p < 0.05) existed among the plant powders andthe concentration. A 100% mortality rate was obtained within 7 days when A. ringens was applied at 0.4 and 0.6 g/20 g of paddy. S. hispidus was able to effect 100% mortality only at 0.6 g. This shows that A. ringens had the greatest insecticidal activity while the least effective was K. ivorensis. Adult emergence shows that more adult S. cerealella emerged from the control (40.3) which was significantly higher (p < 0.05) than others. Fewer adults emerged from paddy treated with plant powder with the least in A. ringens. Generally, adult emergence reduced with an increase in the concentration of powder. The extract from all the four plants tested against S. cerealella was able to effect 100% mortality of the adult moths within 24 h of application at all concentrations. Significant differences (p < 0.05) existed among all the different plant powders in terms of weight loss. The weight loss in paddy was significantly higher (p < 0.05) in the control (57.7%) than others. Weight loss was least in paddy treated with A. ringens at 0.4g/20 g of paddy with 2.2%. Generally, weight loss decreased with increase in powder concentration. The treatment with the highest adult emergence (control) also had the highest weight loss, while the treatment with the lowest adult emergence (A. ringens) had the lowest weight loss.     

The effect of population density on the reproduction ofTrichogramma japonicum Ashmead (Hymenoptera: Trichogrammatidae)

When a fixed number of the hosts, the eggs of the almond moth were exposed experimentally to various numbers of the parasites, Trichogramma japonicum, the following changes were observed with increasing parasite density:

1. The percentage of parasitism rises and approaches to 100 with gradually diminishing rate.
2. The number of parasite progeny increases and reaches a maximum, then decreases gradually.
3. The number of eggs laid per parasite female decreases gradually.
4. The proportion of hyperparasitized hosts progressively rises. The frequency distribution of parasite eggs in a host is of an intermediate type between random and uniform.
5. The competition among parasite larvae becomes severe. The progressive rise in mortality, the declining percentage of females in progeny and the emergence of stunted adults at the higher densities are observed.

In connection with both the nature of the parasitizing behaviour of adult and that of the competition among larvae, the nature of the density effect on the parasite population was discussed.     

Life history of the Asian longhorn beetle Anoplophora glabripennis (Coleoptera Cerambycidae) in southern Europe

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Seasonal biological variation in some leaf-miner parasites in the genus Achrysocharoides (Hymenoptera, Eulophidae)

ABSTRACT.

• 1 Most Achrysocharoides species and their Phyllonorycter hosts (Lepidoptera, Gracillariidae) have two generations per year in Britain.
• 2 In those species with separate sex broods, peak male emergence tends to be earlier than peak female emergence. This female emergence lag is shorter in the second generation.
• 3 The mean brood size in the second generation is significantly smaller than in the first in A.cilla males and females, A.latreilli females, mixed sex broods of A.atys, and A.carpini females. A.cilla, A.latreilli and A.niveipes generally have a significantly greater proportion of males in the second generation, but A.atys does not.
• 4 There is a shift to killing later instar Phyllonorycter larvae in the second generation, when a much higher percentage parasitism is generally achieved.
• 5 The intergeneration differences in sex ratio and brood size may be explained by a change in oviposition behaviour of females of the first and second generations.

     

Protection of cowpea,Vigna unguiculata L. (Walp.) with Newbouldia laevis (Seem.) extracts against infestation by Callosobruchus maculatus (Fabricius)

Evaluation of protectant ability of Newbouldia laevis (Seem.) extracts against infestation by Callosobruchus maculatus in cowpea, Vigna unguiculata L. (Walp.) was carried out in the laboratory at ambient temperature of 28?±?2?°C and 70?±?5% relative humidity. Extracts from wood ash, leaf, stem and root bark were tested at different concentrations of 0, 1, 2, 3, 4 and 5%. One hundred per cent mortality of adult beetles was achieved at all concentrations within 72?h of treatment with extracts except in wood ash at 1% concentration, but they were significantly different (p?<?0.05) from the controls. All the extracts were still able to cause high beetle mortality after one, two and three months of cowpea storage at high concentrations (4 and 5%) except wood ash, although there was a slight decrease in mortality during the period of storage. All the extracts significantly (p?<?0.05) reduced oviposition and adult emergence of C. maculatus when compared with the controls although the reduction was higher at 5% concentration than others. Adult beetle emergence was completely prevented at higher concentrations (4 and 5%) except in wood ash. Both oviposition and adult emergence increased during the months of storage probably because of the slight reduction in the effectiveness of the extracts. The root bark extract was much more effective in reducing oviposition and adult emergence than others throughout the period of storage. The plant extracts of N. laevis was able to protect the cowpea seeds from damage and prevent weight loss. Cowpea seed damage and weight loss was significantly more (p?<?0.05) in the controls than other for the three-month duration probably because of the more adult emergence. The extracts from N. laevis did not adversely affect the germination of the protected seeds and seed germination ranged from 86.7 to 100%. It has been shown in this study that the extracts of N. laevis were effective against C. maculatus in cowpea although the root bark extract seemed to be the most effective while the wood ash extract was least effective. Their effectiveness, however, slightly decreased during the period of storage. N. laevis could be incorporated into pest management of stored cowpeas since the products are ecologically safe.     

Effects of ultraviolet radiation on the eggs of landlocked Galaxias maculatus (Galaxiidae, Pisces) in northwestern Patagonia

• 1 Ultraviolet radiation (UVR) damages early life stages of several fish species. Galaxias maculatus is a small catadromous fish, with landlocked forms occurring in many lakes within the Nahuel Huapi National Park (Patagonia, Argentina). In this work, the vulnerability of G. maculatus eggs exposed to both natural and artificial UVR was investigated in relation to water transparency.
• 2 Field experiments were performed in two lakes differing in UVR attenuation. Galaxias maculatus eggs were exposed to in situ levels of UVR in quartz tubes incubated at various depths. For laboratory experiments, the eggs were exposed to five levels of artificial UVB radiation.
• 3 Exposure to natural UVR causes various degrees of egg mortality depending on water transparency and incubation depth. In the less transparent lake (K_d320 = 3.08 m^‐1), almost complete mortality was observed near the surface. At a depth of 43 cm the observed mortality was only 22%, but was still significantly different from the dark control. In the most transparent lake (K_d320 = 0.438 m^‐1), almost total mortality was observed in tubes incubated at 2.56 m or shallower. A gradual decline in mortality was recorded from that depth to 3.78 m where the values approached those in the dark control treatments.
• 4 A monotonic relationship between mortality and UV exposure could be observed both in field and laboratory experiments. Using the results from field incubations, a LD₅₀ of 2.5 J cm^‐2 nm^‐1 was estimated. In a few mountain lakes, this value would be exceeded even if the eggs were laid at the maximum depth of the lake. Thus UVR seems a sufficient cause to explain the absence of G. maculatus populations in some mountain lakes. For most lakes, however, UVR is probably one of several important environmental factors, which together determine the habitat suitability.

     

Consumption and food utilization by individual larvae and the population of a wood borer Phymatodes maaki Kraatz (Coleoptera: Cerambycidae)

Summary The consumption and the utilization of food by the individuals and the population of a wood borer, Phymatodes maaki Kraatz feeding on the dead wood of a Japanese wild vine, Vitis coignetiae Pulliat were studied at Mt. Daibosatsu, Yamanashi Pref., central Honshu from 1974 to 1976.As for individuals of P. maaki, the estimates of the ratio of growth to consumption and that of assimilation to consumption were very low, amounting to 1.24 and 3.23% in dry weight, 1.23 and 3.12% in carbon weight, and 16 and 13.6% in nitrogen weight respectively. The ratio of growth to assimilation was estimated at 35% in dry weight, 39% in carbon weight and 118% in nitrogen weight. Dry body weight of the adult was correlated with the amount of consumption of the larva.The parasitism by two Ichneumonidae species seemed to be the main mortality factor of the population of P. maaki. A minimum estimate of mortality from egg stage till emergence was 75%.As for the bioeconomy of the population, waste consumption i.e. the consumption of individuals that died before emergence amounted to 75% of total consumption. The growth efficiency (biomass of adults/total consumption) was 0.24% in dry weight, 0.26% in carbon weight and 3.4% in nitrogen weight. The waste efficiency (waste consumption/biomass of adults) was 310 in dry weight, 285 in carbon weight and 22 in nitrogen weight. Approximately 18% of the dead wood of V. coignetiae was decomposed by the feeding of the population.The dry weight of an adult was inversely correlated with density of larvae in the dead wood from which it emerged, but not significantly correlated with the diameter of the wood. The ratio of adult emergence i.e. the survival rate was inversely correlated with density of larvae, but the mortality by parasitism was not density dependent. This seems to suggest that there was an intraspecific competition for the limited food.     

Emergence pattern,site selection,and seasonal regulation of Onychogomphus costae Selys, 1885 (Odonata: Gomphidae) in northeastern Algeria

Emergence and seasonal regulation of the dragonfly Onychogomphus costae Selys, 1885, were surveyed thoroughly during two consecutive years from two nearby stretches upstream the Seybouse River, northeastern Algeria. The emergence season started in mid-May and lasted 68 and 58 days showing a peak in late May and early June in 2011 and 2012, respectively. During the two years 2011 and 2012, 50% of annual emergence occurred after 25 and 22 days, respectively. Sex ratio was slightly but not significantly male biased. Female exuviae were recorded at higher height than males. Height of the exuviae fixation was positively correlated to support height and head width. Percentage mortality at emergence was mainly due to deformity and predation counting from 7.9% to 9.15% of the total emergent population. The species seasonal regulation is inferred and discussed based on the emergence temporal pattern and larval development.     

Ecological studies on the parasite complex associated with typhlocybine leafhoppers (Homoptera, Cicadellidae)

Abstract.

• 1 The parasite complex associated with nymphal and adult typhlocybine leafhoppers consists of the following: Dryinidae (Aphelopus species), Pipunculidae (Chalarus species) and Diapriidae (Ismarus dorsiger Curtis), the last being parasitic on species of Aphelopus.
• 2 The life cycles and temporal distribution patterns of twenty-nine species of Typhlocybinae are summarized together with the life cycles of British Aphelopus and Chalarus.
• 3 Closely related primary parasite species differ in their adult emergence times. Species differences in adult emergence times of diapausing Chalarus are correlated with species differences in host relations.
• 4 Each primary parasite genus contains both monophagous and polyphagous species. Each polyphagous species shows a distinct ‘preference’ for a particular range of hosts.
• 5 The parasite complexes of different leafhopper communities are compared, and it is concluded that it is the taxonomic composition of the leafhopper communities which is chiefly responsible for the structure and taxonomic composition of their associated parasite complexes.
• 6 Individual species of both Aphelopus and Chalarus show a degree of sensitivity to the physiology of their hosts, so achieving a high degree of synchrony.

     

The effect of superparasitism on development of the solitary parasitoid wasp, Venturia canescens (Hymenoptera: Ichneumonidae)

Abstract.

• 1 The effects of superparasitism on the rate of development, adult size and mortality of Venturia canescens (Hymenoptera: Ichneumonidae) were investigated. Parasitoids were reared from third (L3) and fifth (L5) instars of one of its hosts, Plodia interpunctella (Lepidoptera: Pyralidae) containing one, two or four parasitoid eggs.
• 2 Superparasitism increased the development time of Venturia reared from both instars, but the developmental delay was more evident in wasps from L5 hosts.
• 3 The size of parasitoids from L3 hosts was unaffected by egg number, but wasps from both superparasitized L5 treatments were significantly smaller than those from singly parasitized hosts.
• 4 Parasitoid mortality was significantly higher in L5 than L3, but within instars did not differ significantly with egg number.
• 5 The results confirm that superparasitism may affect the fitness of both the adult female wasp and her progeny, and should therefore be incorporated into models of superparasitism as an adaptive foraging strategy.

     

Pupal overwintering,diapause and development in two species of Spilosoma

• 1 Pupae of Spilosoma lubricipeda (L.) and S. lutea (Hufn.) were studied in order to develop a method for estimating the date of emergence of the moths from temperature data. Diapausing pupae stored at 4–5°C for 157 and 171 days showed the fastest development on subsequent incubation at 20°C indicating that diapause had been completed in cold storage.
• 2 Pupae formed in August and October completed diapause in a ventilated insec-tary in March and early April respectively. A 4-month spread in pupation dates was compressed by diapause and low winter temperatures into a 7-day spread in mean emergence dates for S. lubricipeda and a 17-day spread for S. lutea.
• 3 In the insectary, estimated mean emergence dates differed from observed dates by an average of 3.7 days for S. lubricipeda and 2.4 days for S. lutea. Pupae were over-wintered outdoors in S. England and in Scotland. Observed mean dates of moth emergence varied with altitude and latitude, and differed from estimated dates for S.lubricipeda by an average of 5.5 days.
• 4 Mortality did not exceed 30% except in two years in batches kept in wet boxes outdoors at Achnagoichan which is probably beyond the breeding range of both species in Britain. In the laboratory some pupae survived exposure to — 16°C for 192 h suggesting that winter mortality alone does not control the survival of these species at Achnagoichan.

     

Density-dependent regulation of Aedes cantans (Diptera: Culicidae) in natural and artificial populations

Abstract.

• 1 Mortality and size variation (siphon length) in Aedes cantans larvae were examined in natural populations in northern England in 1989 and 1990.
• 2 Under crowded conditions, density-dependent competition led to reduction in the size of both larvae and adults and increased larval mortality.
• 3 Larvae were also maintained in cages in the field at different densities. Results paralleled those for the natural populations in the ponds; larvae maintained at high densities showed increased mortality and reduced size.
• 4 Possible density-dependent factors leading to mortality and size reduction include cannibalism and contact inhibition leading to food shortages.
• 5 The main density-independent factor contributing to larval mortality was habitat desiccation.