OBSERVATIONS ON LIFE HISTORY AND SEX RATIO VARIABILITY OF EUPTEROMALUS DUBIUS (HYMENOPTERA: PTEROMALIDAE), A PARASITE OF CYCLORRHAPHOUS DIPTERA

1976 ◽  
Vol 108 (11) ◽  
pp. 1267-1274 ◽  
Author(s):  
H.G. Wylie
Keyword(s):  
Life History ◽  
Sex Ratio ◽  
Lower Percentage ◽  
Female Progeny ◽  
History Of ◽  
Ratio Change

AbstractFemales of Eupteromalus dubius (Ashm.) oviposit on pupae of cyclorrhaphous Diptera and the larvae develop gregariously as ectoparasites. Details of the life history of E. dubius are described. A progressively lower percentage of female progeny of E. dubius matures as the parasite:host ratio increases. Three mechanisms that may cause this sex ratio change are examined and discussed.

Population dynamics of Stenothoe valida Dana, 1852 (Amphipoda, Stenothoidae) at Cheongsapo beach of Busan, Republic of Korea

Crustaceana ◽  
2021 ◽  
Vol 94 (4) ◽  
pp. 413-429
Author(s):  
Ye Ji Lee ◽  
Won Gyu Park
Keyword(s):  
Population Dynamics ◽  
Life History ◽  
Sex Ratio ◽  
Brood Size ◽  
Ovigerous Female ◽  
Seasonal Pattern ◽  
Recruitment Rate ◽  
Republic Of Korea ◽  
Female Size ◽  
History Of

Abstract The population dynamics of Stenothoe valida Dana, 1852 were studied at Cheongsapo beach of Busan, Republic of Korea, from March 2019 to March 2020. Sampling was conducted once a month at low tide during spring tides. Specimens were grouped by the cephalic length at 0.025 mm intervals, and classified into four categories: females, ovigerous females, males and juveniles. The sex ratio, defined as females : total males + females, exceeded 0.5 during most of the study period. Brood size was significantly coupled with ovigerous female size. Two to four cohorts appeared at each study period. New cohorts occurred at almost every sampling except in the samples Jun-2, and Nov-2. Life span was estimated at 1-2 months. The juvenile ratio, the ratio of ovigerous females, and the recruitment rate estimated by FiSAT were commonly high in summer and winter. The life history of S. valida was not coupled with water temperature, but had a strong seasonal pattern.

SEX RATIO VARIABILITY OF MUSCIDIFURAX ZARAPTOR (HYMENOPTERA: PTEROMALIDAE)

1979 ◽  
Vol 111 (1) ◽  
pp. 105-109 ◽  
Author(s):  
H. G. Wylie
Keyword(s):  
Sex Ratio ◽  
House Fly ◽  
Female Parasite ◽  
Differential Survival ◽  
Female Progeny ◽  
Male And Female ◽  
Ratio Change

AbstractFemales of Muscidifurax zaraptor K. & L. produce a smaller percentage of female progeny as the ratio of ovipositing females to hosts (house fly pupae) increases. Delays in oviposition are apparently responsible for the sex ratio change, because they reduce the percentage of fertilized eggs, i.e. female eggs, that the parasites lay. Delays increase in frequency as the parasite:host ratio increases, and result mostly from interference among the ovipositing females; the interference is mostly or entirely physical. Solitary females of M. zaraptor produce slightly fewer though not significantly fewer female progeny when low host densities delay oviposition; more tests would be required to confirm this effect. There is no evidence for differential survival of the male and female parasite larvae on superparasitized hosts.

Dynamics of an Exploited Population of Lake Whitefish (Coregonus clupeaformis)

1977 ◽  
Vol 34 (7) ◽  
pp. 942-953 ◽  
Author(s):  
Graham Bell ◽  
Paul Handford ◽  
Carl Dietz
Keyword(s):  
Life History ◽  
Sex Ratio ◽  
Age Structure ◽  
Annual Rate ◽  
Multiple Regression Equation ◽  
Coregonus Clupeaformis ◽  
Lake Whitefish ◽  
History Of ◽  
Almost All ◽  
Key Words Population Dynamics

The life history of the exploited lake whitefish (Coregonus clupeaformis) population of Lesser Slave Lake, Alberta, is described. Mean age is high, having increased under continued exploitation during the last 30 yr. A method of estimating the population age structure is described. The apparent annual rate of survival of adult fish has fluctuated markedly, but on average seems to lie in the interval 0.40–0.50; the annual rate of natural survival is estimated to be 0.53. Juveniles survive better than adults. Rate of survival during the 1st yr of life was estimated to be about 0.0002. Maturity was late, the median age at first reproduction being 6–61/2 yr. The regressions of fecundity on age and length are described; length now contributes almost all the attributable variance to maturity and fecundity. The sex ratio fluctuates in time; this is caused by the fluctuations in age structure, since sex ratio varies with age. The relationship between sex ratio and age is used to calculate the relative rates of survival of male and female fish.These data are used to construct a life table and to compute population parameters. It is inferred that the ability of the population to respond to exploitation has been eroded during the last 30 yr. In some respects, the life history of the Lesser Slave Lake stock appears to be unusual.After about 30 yr of large-amplitude oscillation the whitefish population collapsed in 1965. This does not seem to have been caused by chronic overfishing. In the first place, the rate of fishing mortality is no more than moderate. Secondly, a multiple regression equation describing whitefish catch in 48 other Alberta lakes in which there has been no overall decline in catch successfully predicts the observed mean catch at Lesser Slave Lake. The oscillations in catch are claimed to reflect a limit cycle in the abundance of the whitefish, driven by a lagged relationship between a predator (the fishermen) and its prey (the whitefish). Whether or not this cycle was deterministically stable, such behavior will inevitably put the population in risk of extinction during troughs in the cycle. We suggest that current management policies may encourage the destabilization of whitefish populations, and we propose a remedy. Key words: population dynamics, population regulation, life history, exploitation, survival, fecundity, Coregonus clupeaformis

Variability in the life history of Unionicola crassipes, a sponge-associated water mite (Acari: Unionicolidae)

1990 ◽  
Vol 68 (6) ◽  
pp. 1227-1232 ◽  
Author(s):  
Heather C. Proctor ◽  
Gordon Pritchard
Keyword(s):  
Life History ◽  
Sex Ratio ◽  
Emerging Adults ◽  
Life Histories ◽  
Population Decline ◽  
Early Summer ◽  
Water Mites ◽  
Water Mite ◽  
History Of ◽  
Female Bias

The life history of a member of the widely distributed Unionicola crassipes complex (Acari: Unionicolidae) in a foothills pond in Alberta, Canada, differs from those previously described for this taxon. Two years are required for a female to develop from an egg to an ovipositing adult. Fertilized females overwinter and oviposit in the sponge Eunapius fragilis in early May. Larvae emerge in late May to early June and parasitize chironomids of the genus Tanytarsus. Engorged larvae drop from their insect hosts and return to sponges for the protonymph resting stage. Active, predaceous deutonymphs develop from protonymphs in early summer. Deutonymphs overwinter and enter the tritonymph resting stage, also in sponges, in early May. Summer adults emerge from the tritonymph stage in late May to early June. Males emerge first, but there is an overall female bias to the sex ratio of emerging adults. Growth of sclerotized and unsclerotized parts occurs in adults over the summer, during which time females appear to suffer greater mortality than males, because the sex ratio is 1:1 in September. It is primarily mated females that overwinter for a second time. A population decline in the summer of 1987 was correlated with degeneration of sponges; variation in the life histories of sponge-associated water mites is discussed in light of this correlation.

LIFE HISTORY OF CRICOTOPUS MYRIOPHYLLI OLIVER (DIPTERA: CHIRONOMIDAE) IN THE OKANAGAN VALLEY, BRITISH COLUMBIA

1993 ◽  
Vol 125 (6) ◽  
pp. 979-985 ◽  
Author(s):  
Ian V. MacRae ◽  
Richard A. Ring
Keyword(s):  
British Columbia ◽  
Life History ◽  
Sex Ratio ◽  
Larval Instar ◽  
Field Observations ◽  
Laboratory Rearing ◽  
The Third ◽  
First Instar ◽  
History Of ◽  
Rate Of Emergence

AbstractThe life history of Cricotopus myriophylli Oliver is described from both field observations and laboratory rearing of field-collected larvae. The species appears to be univoltine with four larval instars and has a sex ratio of ca. 2:1, males to females. Emergence begins in late May in British Columbia and continues until mid-September, with first-instar larvae present in the field from mid-June to mid-August. Water temperature does not appear to influence the rate of emergence. In the laboratory at 21 °C, larvae complete each of the third and fourth instars in 10–14 days. Cricotopus myriophylli overwinters primarily in the third larval instar, although second and fourth instars were also recovered in field-collected samples. First-instar larvae and eggs were not recovered from winter samples. This species does not appear to undergo a true diapause.

LIFE HISTORY OF THE APHID HYPERPARASITOID ASAPHES VULGARIS WALKER (PTEROMALIDAE): POSSIBLE CONSEQUENCES ON THE EFFICACY OF THE PRIMARY PARASITOID APHIDIUS NIGRIPES ASHMEAD (APHIDIIDAE)

1994 ◽  
Vol 126 (6) ◽  
pp. 1493-1497 ◽  
Author(s):  
Jacques Brodeur ◽  
Jeremy N. McNeil
Keyword(s):  
Life History ◽  
Sex Ratio ◽  
Life Span ◽  
Lifetime Fecundity ◽  
Primary Parasitoid ◽  
Laboratory Conditions ◽  
Aphidius Nigripes ◽  
Reproductive Life ◽  
History Of ◽  
The Impact

AbstractAspects of the life history of the aphid hyperparasitoid Asaphes vulgaris Walker, when reared on Aphidius nigripes Ashmead, were investigated under laboratory conditions. Longevity was significantly related to temperature and to the sex of adults. Female life span was about 4 months at 15 °C compared with 46 days at 25 °C; under the same conditions male longevity was 66 and 19 days, respectively. Females started to oviposit in aphid mummies upon eclosion and lifetime fecundity was high, reaching 1433 offspring. The sex ratio (proportion of males) was low early in reproductive life but rose sharply after several weeks. The implications of these results on the efficacy of A. nigripes in the potato agrosystem are discussed. It is suggested that high hyperparasitoid fecundity and longevity might play a role in reducing the impact of the primary parasitoid.

On the Biology and Life History of Rhabditis Pellio (Nematoda)

Parasitology ◽  
1933 ◽  
Vol 25 (3) ◽  
pp. 296-307 ◽  
Author(s):  
G. W. Otter
Keyword(s):  
Life History ◽  
Sex Ratio ◽  
Egg Production ◽  
Culture Media ◽  
Natural State ◽  
Cultural Conditions ◽  
History Of ◽  
Head Segment ◽  
Favourable Environment ◽  
Rhabditis Pellio

1. Accurate measurements were made of adults, larvae and eggs of Rhabditis pellio, representing an average selection for comparison with Johnson's figures.2. The most satisfactory method of culturing the nematodes was in hanging drops, in a medium free from an excess of putrefying bacteria.3. A medium poor in food was found to prolong life (up to 40 days), while a rich medium quickened up the life processes thereby causing death sooner. It is probably partial starvation which prevents the larvae from becoming mature while in the living earthworm.4. In a medium favourable for prolonging life, the males were found to live about one-third as long as the females (F generation). It is probable that the females only live for about 4–8 days in a decaying earthworm after attaining maturity.5. The maximum number of eggs laid per female was 257 (F generation) and 197 (F1 generation). It is probable that between 150 and 300 eggs are laid per female in the natural state. No information was obtained regarding the effect of the various media on egg production.6. In most cases the females died when spent of eggs.7. Vivipary is considered to be due to a favourable environment probably aided by a high temperature.8. Larvae were found to be more susceptible to cultural conditions than the adults, especially those (F generation) which were not bred from females in culture media. The growth-rate of F1 generation larvae was found to be slightly faster in a natural medium, such as earthworm broth, than in peptone.9. The chief food is considered to be bacteria.10. During this work R. pellio behaved entirely as a bisexual species. A few cases of copulation were observed, showing that some of the males had not lost their “sexual instinct.”11. Rhabditis pellio is considered to be a species in which hermaphroditism is just commencing and in which true males and females exist together with hermaphrodite females whose numbers fluctuate, the degree of hermaphroditism possibly bearing some relation to the sex ratio.12. The sex ratio was about 1 ♂: 2 ♀♀, in both the F and F1 generations, but varied considerably. There were a few cases in which the male proportion was equal, or higher, than the female.13. Four different species of British earthworms were examined, each being infected by Rhabditis pellio to a varying extent. Eisenia foetida was, however, rarely infected. Size of the earthworm, in proportion, played no part regarding the degree of infection. There is an indication that the head (segment I to the beginning of the clytellum) is the most heavily infected region.14. A few specimens (larval stage) of an Ascarid, a species of Porrocaecum, a parasite of small mammals and birds, were found in three of the species of earthworms examined.15. A probable course of the life history is given, based on this work and that of Johnson (1913).

Observations on the life history of the scorpion Urodacus abruptus (Scorpionidae), and the analysis of its home sites

1966 ◽  
Vol 14 (3) ◽  
pp. 383 ◽  
Author(s):  
GT Smith
Keyword(s):  
Life History ◽  
Sex Ratio ◽  
Numerical Stabilization ◽  
Adult Sex Ratio ◽  
Discrete Population ◽  
History Of ◽  
Black Mountain ◽  
Selection Of

The life history of the scorpion was worked out for a discrete population on Black Mountain near Canberra, A.C.T. The biology was unusual because of an unexpected longevity and a highly imbalanced adult sex ratio. A clear selection of favoured home sites was demonstrated, but it was also shown that availability of food limited the population before all potential home sites were occupied. A mechanism of numerical stabilization dependent on the regulation of recruitment is discussed.

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