Studies on Life Fecundity Tables of Tobacco Leaf Eatingcaterpillar, Spodoptera Litura (Fabricius) On Tobacco, Nicotiana Tabacum (Linnaeus)

Studies on Life tables of Spodoptera litura, were carried out on bidi tobacco cv ABD-101 under laboratory condition at 26 ± 1 °C temperature at Bidi Tobacco Research Station, Anand Agricultural University, Anand (Gujarat). The results on number of individuals survived during development revealed that there was no mortality during egg stage and the maximum durations of egg, larva and pupa were 4, 22 and 14 days, respectively. The number that survived from 100 eggs to adult emergence was 76. The pre-oviposition period was ranged from 41 to 42 days of pivotal age. Females contributed highest number of progeny (mx = 328.12) in the life cycle on the 45th day of pivotal age. The net reproductive potential (Ro) was 758.93 females with the mean length of generation period (T) of 45.67 days. The innate capacity for increase (rm) and finite rate of increase () were found to be 0.1462 and 1.1574 females/ female/ day, respectively with a weekly multiplication rate (λ)7 of 2.78 times. The hypothetical F2 females were found to be 575974.70. Results on per cent contribution of different growth stages in stable age distribution revealed that the egg stage contributed was maximum (52.64%), while the contribution of larvae, pupae and adults were 45.86, 1.36 and 0.12, respectively at stable age distribution of S. litura on tobacco cv. ABD-101.

Change in Life Expectancy and Stable Age Distribution of the Diamondback Moth, Plutella Xylostella (L.) After Indoxacarb Treatment

Change in Life Expectancy and Stable Age Distribution of the Diamondback Moth,Plutella Xylostella(L.) After Indoxacarb TreatmentUsing high doses of insecticides is very dangerous for the environments and for humans. Decreased concentrations are necessary. Insecticides have lethal and sublethal effects. The aim of the present study was to determine the behavior ofPlutella xylostellawhen exposed to sublethal doses of indoxacarb in terms of the age-specific fecundity (mx), life expectancy (ex) and stable age distribution (Cx). Also, the effects of sublethals on the pre-oviposition, oviposition and post-oviposition period of this insect were investigated. The results show that exposure to this insecticide decreased the age-specific fecundity (mx) and life expectancy (ex) of the insect. Although the pre-oviposition period was delayed in the treated groups, the post-oviposition period significantly decreased when exposed to LC10and LC25doses (the dose concentrations killed 10 and 25% of the populations) of indoxacarb. The oviposition period did not change. Furthermore, sublethal concentrations of the applied insecticide caused changes in the exposed structure.

STUDI LALAT PENGOROK DAUN LIRIOMYZA SPP. PADA PERTANAMAN BAWANG DAUN, DAN PARASITOID OPIUS CHROMATOMYIAE BELOKOBYLSKIJ & WHARTON (HYMENOPTERA: BRACONIDAE)

Studies on Leafminer Liriomyza spp. in Green Onion Fields, and Parasitoid Opius chromatomyiae Belokobylskij & Wharton (Hymenoptera: Braconidae). Field studies were conducted to determine population abundance of leafminers and their parasitoids in green onion fields in Puncak, West Java. In addition to that, laboratory studies were carried out to determine demographic parameter of Opius chromatomyiae as well as response of parasitoid to increasing host density. Results revealed that green onions were infested by two species of leafminers, Liriomyza huidobrensis and Liriomyza chinensis. Leafminer flies emerged from Erwor leaves (54.5) were significantly higher than those of RP leaves (18.65) (P = 0.0005). However, number of leafminer flies caught on sticky traps was not statistically different (P = 0.297). Two species of parasitoid, Hemiptarsenus varicornis and O. chromatomyiae, were associated with leafminers in green onion fields. Higher number of parasitoids emerged from Erwor leaves (13.68) as compared to RP (6.90) (P =0.0007 ). However, level of parasitization were 24.36% on Erwor and 28.45% on RP, and was not significantly different (P = 0.387). Laboratory studies indicated that net reproduction (Ro) of O. chromatomyiae was 28.55, generation time (T) 15.96 days, intrinsic growth rate 0.21, and total of reproductive value 223.64. The stable age distribution of parasitoid were 37.93% eggs, 24.92% larvae, 20.36% pupae and 16.78% adults. The parasitoid showed functional response type II to increasing host density, with a = 0.08 and Th = 2.58.

Using multiple abundance estimators to infer population trends in Atlantic Puffins

We used five techniques to estimate the number of Atlantic Puffins (Fratercula arctica) using a study plot on Gull Island, Newfoundland, during the 2000 breeding season. Grubbing of burrows yielded an estimate of a breeding population of 522 (95% CI: 364–668) Atlantic Puffins on this plot. Attendance counts of birds standing on the plot consistently underestimated the breeding population. A closed-population estimator with sighting heterogeneity estimated that of the 535 Atlantic Puffins banded since 1997, 370 (336–404) used the plot in 2000. Using 370 birds as the marked population, a corrected Lincoln–Petersen index estimated a total population of 1712 (1233–2191) based on captured birds. Based on resights of birds, ratios of banded birds to total attendance estimated 2927 (2608–3335), and the Bowden estimator gave 3502 (3054–3950) Atlantic puffins. We projected an age-based matrix using literature values, and extracted the proportions of nonbreeding birds and young birds expected at a stable age distribution and compared the proportions with observed values. Based on the large number of nonbreeders suggested by the abundance estimates, we suspect that this population (i) is stable or increasing, (ii) includes breeding-age Atlantic Puffins that do not breed, and (iii) has been enjoying high fecundity in recent years.

Tsetse fly (Diptera: Glossinidae) population dynamics and the estimation of mortality rates from life-table data

The estimation of tsetse fly mortality rates from life-table data is central to opulation dynamics studies and to the development of tsetse fly control programmes. For a population at equilibrium with a stable age distribution, the age-specific mortalities may be estimated directly from the number of individuals in each age class, but a correction must be applied when the population is growing or declining. Furthermore, if the mortality rates are changing with time, inaccuracies will be introduced into estimates of the mortality rates derived from the age structure of the population since the population will take time to reach a new stable age distribution. In this paper we use the Euler-Lotka equation, which relates the age-specific mortality and fecundity to the overall growth rate of the population, to study the loss rate of the tsetse fly Glossina pallidipes (Austen) as a function of pupal mortality, adult mortality and mortalities applied to each age class seperately. We then present a simulation model in order to quantity and to set limits on the precision of estimates of mortalities when the mortalities are themselves changing.

The growth and composition of branching populations

A single-type general branching population develops by individuals reproducing according to i.i.d. point processes on R+, interpreted as the individuals' ages. Such a population can be measured or counted in many different ways: those born, those alive or in some sub-phase of life, for example. Special choices of reproduction point process and counting yield the classical Galton–Watson or Bellman–Harris process. This reasonably self-contained survey paper discusses the exponential growth of such populations, in the supercritical case, and the asymptotic stability of composition according to very general ways of counting. The outcome is a strict definition of a stable population in exponential growth, as a probability space, a margin of which is the well-known stable age distribution.

The growth and composition of branching populations

A single-type general branching population develops by individuals reproducing according to i.i.d. point processes on R +, interpreted as the individuals' ages. Such a population can be measured or counted in many different ways: those born, those alive or in some sub-phase of life, for example. Special choices of reproduction point process and counting yield the classical Galton–Watson or Bellman–Harris process. This reasonably self-contained survey paper discusses the exponential growth of such populations, in the supercritical case, and the asymptotic stability of composition according to very general ways of counting. The outcome is a strict definition of a stable population in exponential growth, as a probability space, a margin of which is the well-known stable age distribution.