Development of Cotesia orobenae Forbes (Hymenoptera: Braconidae) in its Host, Evergestis rimosalis (Guenée) (Lepidoptera: Pyralidae)

2001 ◽  
Vol 36 (1) ◽  
pp. 9-16
Author(s):  
L. T. Kok ◽  
J. A. Acosta-Martinez
Keyword(s):  
Sex Ratios ◽  
Host Density ◽  
Female Offspring ◽  
Developmental Time ◽  
The Other ◽  
Optimal Temperature ◽  
Density Effects ◽  
Adult Parasitoid ◽  
Early Instar ◽  
Lepidoptera Pyralidae

Temperature and host density effects on the development of Cotesia orobenae Forbes (Hymenoptera: Braconidae), and its parasitism of the cross-striped cabbageworm, Evergestis rimosalis (Guenée) (Lepidoptera: Pyralidae), were investigated. Time for adult parasitoid emergence from cocoon masses of C. orobenae maintained at 15, 20, 25, 30 and 35°C and a photoperiod of 15:9 (L: D) was inversely related to temperature. Parasitoid emergence exceeded 86% for all temperatures except that at 35°C. Development of C. orobenae on early-instar hosts was best at 20 and 25°C. Although the shortest developmental time was observed at 35°C, survival of both parasitoid and host was low at this temperature. At 15°C, the parasitoid was not very active, and developmental time was the longest among the temperatures tested. Percent of host larvae parasitized was significantly higher at 20 and 25°C than the other temperatures tested. Females were short-lived and oviposited an average of 118 and 136 eggs at 20 and 25°C, respectively. Females died after 24 h of being placed in the oviposition chamber at 30 and 35°C. At 15°C they lived longer, but did not parasitize host larvae provided. Virgin females produced only male progeny. Mated females produced slightly more female offspring than males. Sex ratios of progeny from females paired with single or multiple males were not different. Percentage parasitization of host larvae between treatments differed for the first day, but not the second day. Fecundity of C. orobenae exposed to five host densities (5, 10, 15, 20, and 25 per parasitoid) showed significant differences in percent parasitization among the treatments. Percentage parasitization was highest with five and 10 hosts per parasitoid. The highest number of parasitoid cocoons recovered per cocoon mass was obtained with 10 hosts. The data indicate that optimal temperature for C. orobenae oviposition, development, and parasitism of its host is between 20 to 25°C.

scholarly journals Pengaruh Suhu terhadap Perkembangan Pradewasa Parasitoid Eriborus argenteopilosus Cameron (Hymenoptera: Ichneumonidae)

2012 ◽  
Vol 13 (3) ◽  
pp. 250
Author(s):  
Novri Nelly ◽  
Trimurti Habazar ◽  
Rahmat Syahni ◽  
Damayanti Buchori
Keyword(s):  
Survival Rate ◽  
Temperature Effect ◽  
Development Time ◽  
Degree Days ◽  
Degree Day ◽  
Adult Parasitoid ◽  
Different Temperatures ◽  
Lepidoptera Pyralidae

Temperature effect on development time of the preadult parasitoid Eriborus argenteopilosus Cameron(Hymenoptera: Ichneumonidae) were studied to know development time, degree days and survival rate.Crocidolomia pavonana (Fabricius)(Lepidoptera: Pyralidae) larvae was exposed to E. argenteopilosus female andreared at four different temperatures i.e 160C, 200C, 250C and 300C. Data were analyzed using anova and linearregression to calculate degree day. At 200C E. argenteopilosus showed the highest degree day and survival rate(18.67 %), while at 300C nothing adult parasitoid emergenced. Degree day to development time of parasitoid attemperature 200C i.e fase egg-adult: 300.05; egg-pupae 173.35; pupae-adult 171.

scholarly journals Generalized conditions for coexistence of competing parasitoids on a shared host

2020 ◽  
Author(s):  
Abhyudai Singh
Keyword(s):  
Discrete Time ◽  
Life Histories ◽  
Host Density ◽  
Host Community ◽  
Reproduction Rate ◽  
Parasitoid Species ◽  
Slow Increase ◽  
Time Formalism ◽  
Adult Parasitoid ◽  
The Stability

AbstractMotivated by the univoltine life histories of insects residing in the temperate-regions of the world, there is a rich tradition of modeling arthropod host-parasitoid interactions using a discrete-time formalism. We introduce a general class of discrete-time models for capturing the population dynamics of two competing parasitoid species that attack the same vulnerable stage of the host species. These models are characterized by two density-dependent functions: an escape response defined by the fraction of hosts escaping parasitism; and a competition response defined by the fraction of parasitized hosts that develop into adult parasitoids of either species. Model analysis reveals remarkably simple stability conditions for the coexistence of competing parasitoids. More specifically, coexistence occurs, if and only if, the adult host density increases with host reproduction rate, and the log sensitivity of the competition response is less than half. The latter condition implies that any increase in the adult parasitoid density will result in a sufficiently slow increase in the fraction of parasitized hosts that develop into parasitoids of that type. We next consider a model motivated by differences in parasitism risk among individual hosts with risk from the two parasitoid species assumed to be independently distributed as per a Gamma distribution. In such models, the heterogeneity in host risk to each parasitoid is quantified by the corresponding Coefficient of Variation (CV). Our results show that parasitoid coexistence occurs for sufficiently large reproduction rate, if and only if, the sum of the inverse of the two CV squares is less than one. This result generalizes the “CV greater than one” rule that defined the stability for a single parasitoid-host system to a multi parasitoid-host community.

scholarly journals Extraordinary morphological changes in valve morphology during the ontogeny of several species of the Australian ostracod genus Bennelongia (Crustacea, Ostracoda)

2013 ◽  
Author(s):  
Patrick De Deckker ◽  
Koen Martens
Keyword(s):  
Adult Stage ◽  
Morphological Changes ◽  
The Other ◽  
Left Valve ◽  
Ventral Region ◽  
Valve Morphology ◽  
Other Hand ◽  
Early Instar ◽  
Juvenile Stages

Ostracods belonging to the genus Bennelongia differ much in valve morphology between adults and juveniles. Adult valves are asymmetrical, characterised by a beak-like feature in the antero-ventral region of the left valve, and, with some notable exceptions, mostly have smooth or weakly-ornamented valves. Juvenile specimens, on the other hand, have valves that are almost symmetrical, with no beak-like feature and are often heavily ornamented.We have examined the last 3 - 4 juvenile stages of 6 Bennelongia species from 5 different lineages, in order to decipher the types of external valve ornamentation and their recurrences during ontogeny and across lineages. It is clear that ornamentation is more prevalent at the early instar stages compared to the last 2 pre-adult stages, and especially when compared to the adult stage itself.We also examined the surprising presence of a calcified inner lamella with a prominent inner list in the pre-adult stages of Bennelongia species, that is usually absent in juveniles of other ostracods, thus questioning if heterochronic processes have provided an intermediate valve morphology between the simple (normal) cypridinid juvenile state and the heavily derived and modified state of adult Bennelongia.We discuss the possible (speculative) functionality of the ornamentation in juveniles.

scholarly journals Recruitment sex ratios in gray-tailed voles (Microtus canicaudus) in response to density, sex ratio, and season

2003 ◽  
Vol 81 (8) ◽  
pp. 1306-1311 ◽  
Author(s):  
Monica L Bond ◽  
Jerry O Wolff ◽  
Sven Krackow
Keyword(s):  
Population Density ◽  
Sex Ratio ◽  
Resource Competition ◽  
Sex Ratios ◽  
Female Offspring ◽  
High Population ◽  
Reproductive Value ◽  
High Population Density ◽  
Adult Sex Ratio ◽  
Sex Ratio Adjustment

We tested predictions associated with three widely used hypotheses for facultative sex-ratio adjustment of vertebrates using eight enclosed populations of gray-tailed voles, Microtus canicaudus. These were (i) the population sex ratio hypothesis, which predicts that recruitment sex ratios should oppose adult sex-ratio skews, (ii) the local resource competition hypothesis, which predicts female-biased recruitment at low adult population density and male-biased recruitment at high population density, and (iii) the first cohort advantage hypothesis, which predicts that recruitment sex ratios should be female biased in the spring and male biased in the autumn. We monitored naturally increasing population densities with approximately equal adult sex ratios through the spring and summer and manipulated adult sex ratios in the autumn and measured subsequent sex ratios of recruits. We did not observe any significant sex-ratio adjustment in response to adult sex ratio or high population density; we did detect an influence of time within the breeding season, with more female offspring observed in the spring and more male offspring observed in the autumn. Significant seasonal increases in recruitment sex ratios indicate the capacity of female gray-tailed voles to manipulate their offspring sex ratios and suggest seasonal variation in the relative reproductive value of male and female offspring to be a regular phenomenon.

Host density effects on efficacy of entomopathogenic nematodes against white grub (Coleoptera: Scarabaeidae) species

2012 ◽  
Vol 22 (1) ◽  
pp. 117-123 ◽  
Author(s):  
Lemma Ebssa ◽  
Eugene M. Fuzy ◽  
Matthew W. Bickerton ◽  
Albrecht M. Koppenhöfer
Keyword(s):  
Entomopathogenic Nematodes ◽  
Host Density ◽  
White Grub ◽  
Density Effects

Unequal sex ratios in longline catches

2001 ◽  
Vol 81 (1) ◽  
pp. 187-188 ◽  
Author(s):  
P. Wirtz ◽  
T. Morato
Keyword(s):  
Sex Ratio ◽  
Feeding Behaviour ◽  
Sex Ratios ◽  
The Other ◽  
Size Difference ◽  
Longline Fishery ◽  
Significant Bias ◽  
Different Response ◽  
The Given

There is sometimes a significant bias in the sex ratio of fish caught by longline. Usually, more females than males are caught. The possible reasons for unequal sex ratios in longline catches are listed and discussed. One sex could be more common in the area where the fishery takes place because there really is an unequal sex ratio in the population or because the other sex preferentially occurs in different places. Alternatively, longline fishery might preferentially catch one of the sexes. This could be a result of size difference between the sexes and thus a different response to the given hook size or bait size. Finally, sexes could differ in their feeding behaviour. There is growing evidence that females—not only of fish—are ‘energy maximizers’: they find food faster and spend more time feeding than do males. Thus, fishing methods using bait are likely to catch a higher proportion of females than fishing methods that do not use bait.

Preferences and Performance of Erythroneura sudra (Homoptera: Cicadellidae) on Five Fruit Tree Species (Rosaceae)

2020 ◽  
Vol 49 (4) ◽  
pp. 931-937
Author(s):  
Xunbing Huang ◽  
Yueyue Wang ◽  
Zehua Zhang
Keyword(s):  
Relative Density ◽  
Plant Species ◽  
Tree Species ◽  
Management Strategies ◽  
Northern China ◽  
Developmental Time ◽  
Fruit Tree ◽  
The Other ◽  
Significant Damage ◽  
And Performance

Abstract Erythroneura sudra is a leafhopper occurring in northern China, which causes significant damage to fruit. The relationships between E. sudra and five fruit tree species (Rosaceae) were studied for 3 yr. The highest relative density of E. sudra was recorded on leaves of Amygdalus persica L. and Cerasus pseudocerasus Lindl. Likewise, it had the highest survival rate and shortest developmental time when it fed on these two plants species, indicating that they were the most preferred by E. sudra than the other plant species. The relative density and growth performance of E. sudra were negatively correlated with the levels of tannins and flavonoids in the leaves of the host species. Both plant species had relatively lower flavonoids and tannins, and this may have contributed to the enhanced survival and population growth of E. sudra. These results can guide the development of improved management strategies for this pest.

scholarly journals Reproduction and Offspring Sex Ratios Differ Markedly among Closely Related Hyperparasitoids Living in the Same Microhabitats

2019 ◽  
Vol 32 (3) ◽  
pp. 243-251 ◽  
Author(s):  
Jeffrey A. Harvey ◽  
Lucas de Haan ◽  
Oriol Verdeny-Vilalta ◽  
Bertanne Visser ◽  
Rieta Gols
Keyword(s):  
Reproductive Success ◽  
Sex Ratios ◽  
Reproductive Traits ◽  
Female Offspring ◽  
Forest Edge ◽  
Cotesia Glomerata ◽  
Small Scale ◽  
Lifetime Reproductive Success ◽  
Closely Related Species ◽  
Offspring Sex

Abstract Closely related species in nature usually exhibit very similar phylogenetically conserved traits, such as reproduction, behavior and development. Here, we compared fecundity schedules, lifetime reproductive success and offspring sex ratios in three congeneric facultative hyperparasitoid wasps that exhibit several overlapping traits and which co-occur in the same small-scale habitats. Gelis agilis, G. proximus and G. hortensis are abundant in meadows and forest edge habitats in the Netherlands. Gelis agilis is asexual (all female), whereas the other two species reproduce sexually. Here they developed on cocoons of the primary parasitoid Cotesia glomerata. When provided with unlimited hosts, lifetime reproductive success was three times higher in G. proximus than in G. agilis with G. hortensis producing intermediate numbers of offspring. All three species depleted their teneral reserves during their lives. Females of G. proximus and G. hortensis lived significantly longer than females of G. agilis. Offspring sex ratios in young G. proximus mothers were female-biased and marginally male-biased in G. hortensis. As mothers aged, however, the ratio of male:female progeny produced rapidly increased until no daughters emerged later in life. Our results reveal significant differences in reproductive traits among the three species despite them co-occurring in the same microhabitats, being very closely related and morphologically similar. The increase in the production of male progeny by Gelis mothers over time suggests a depletion in sperm number or viability with age. This is especially interesting, given that Gelis species are among the least fecund parasitoids thus far studied. It is likely that in the field most Gelis mothers are probably only able to parasitize a few hosts and to maintain the production of female offspring.

scholarly journals Sperm sex ratio adjustment in a mammal: perceived male competition leads to elevated proportions of female-producing sperm

2020 ◽  
Vol 16 (6) ◽  
pp. 20190929
Author(s):  
Renée C. Firman ◽  
Jamie N. Tedeschi ◽  
Francisco Garcia-Gonzalez
Keyword(s):  
Sex Ratio ◽  
Sex Allocation ◽  
Sex Ratios ◽  
Female Offspring ◽  
Male Competition ◽  
Offspring Sex ◽  
Sex Ratio Adjustment ◽  
Adaptive Adjustment ◽  
Male House

Mammal sex allocation research has focused almost exclusively on maternal traits, but it is now apparent that fathers can also influence offspring sex ratios. Parents that produce female offspring under conditions of intense male–male competition can benefit with greater assurance of maximized grand-parentage. Adaptive adjustment in the sperm sex ratio, for example with an increase in the production of X-chromosome bearing sperm (CBS), is one potential paternal mechanism for achieving female-biased sex ratios. Here, we tested this mechanistic hypothesis by varying the risk of male–male competition that male house mice perceived during development, and quantifying sperm sex ratios at sexual maturity. Our analyses revealed that males exposed to a competitive ‘risk’ produced lower proportions of Y-CBS compared to males that matured under ‘no risk’ of competition. We also explored whether testosterone production was linked to sperm sex ratio variation, but found no evidence to support this. We discuss our findings in relation to the adaptive value of sperm sex ratio adjustments and the role of steroid hormones in socially induced sex allocation.

Tick (Acari: Ixodidae) ecological studies in Tanzania

1986 ◽  
Vol 76 (2) ◽  
pp. 229-246 ◽  
Author(s):  
R. J. Tatchell ◽  
E. Easton
Keyword(s):  
Seasonal Variation ◽  
Host Density ◽  
Dar Es Salaam ◽  
Rhipicephalus Appendiculatus ◽  
Amblyomma Variegatum ◽  
The Other ◽  
Theileria Parva ◽  
Ecological Studies ◽  
Adult Abundance

AbstractTicks were regularly collected from cattle along transects in Sukumaland and the Southern Highlands, Tanzania, and from locations near Tabora, Mbeya, Arusha and Dar es Salaam from 1973 to 1976. Marked seasonal variation in abundance occurred in Rhipicephalus appendiculatus Neumann in the Southern Highlands (but not in Sukumaland) and in Amblyomma variegatum (F.) near Tabora. It was possible to detect Theileria parva antibodies in cattle sera from the Southern Highlands only during the season of R. appendiculatus adult abundance. Despite this there was no evidence of enzootic instability of the disease. The results demonstrate that the behaviour and distributions of these and the other species of ticks found are not fixed and constant but vary according to a complicated interplay of factors as yet imperfectly understood, such as climate and vegetation and host density, susceptibility and grazing habits.

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