The estimation and simulation of variable developmental period,with application to the mosquitoAedes aegypti (L.)

The variability of stage developmental period may be a seminal feature of some insect populations and therefore of importance in management studies. A transfer function technique is described for estimating the frequency distribution of developmental period and simulating the subsequent population dynamics. The technique relates recruitment time series of consecutive stages by an age-specific developmental success function. Approximate statistics, such as the mean, median or mode developmental period, may be determined and the effect of different temperature or density regimes compared.     

Maternal age as a source of variation in the ability of an aphid to produce dispersing forms

Apterous parthenogentic females of the pea aphid, Acyrthosiphon pisum (Harris ), begin to produce alate offspring soon after they have been subjected to crowding. Females which were born early in their own parent's reproductive period respond most strongly to crowding, producing much larger numbers of alatae than their late-born sisters. In contrast, the early-born daughters of most alate females do not produce winged offspring after being crowded. Some of their later-born sisters may produce a few winged individuals, resembling in this respect the late-born daughters of the apterous females. Control of the production of alatae thus begins in the grandparental generation. Risk-spreading by means of differential dispersal becomes a less uncertain venture when local populations can modify their responses to environmental changes by utilizing past as well as present signals from their surroundings.     

On the individual variation of several morphological and physiological characters under different environmental conditions

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Contributions from the Entomological Laboratory, Kyoto University, No. 229.     

The effects of food and density on the nocturnal behaviour ofArion ater andAriolimax columbianus (Pulmonata: Stylommatophora)

The effects of food supply and population density on the nocturnal behaviour of Arion ater and Ariolimax columbianus were investigated. Density did not significantly affect A. ater's level of activity or short-term movement, resting, or feeding. A. columbianus was more active and moved, rested, and fed more frequently when slug density was high. A. ater foraged and rested more often, but fed less when good food was unavailable. Ariolimax's only response to the food regime was to feed more when good food was available. Seasonal changes in the level of activity and behaviour of Arion were evident, whereas Ariolimax's activity and behavioural repertoire were not similarly affected. Arion ater's nightly activity appeared to be mainly food oriented, while Ariolimax columbianus seemed most responsive to slug density during its nocturnal activity periods.     

Fossilized human blood cells from a Hellenistic settlement

The su of human soft tissue over long periods of time after death by mummification is common knowledge. Egyptian and pre-Columbian mummies from America are the best-known examples of this process. The survival of human blood cells, the most fragile of all soft tissue, over a period of about 2200 years by a process of fossilization is a phenomenon which had not been observed previously. Fossilized blood cells were found during the paleopathological examination of skeletons of soldiers buried near a Hellenistic fortress. The fortress had been built on an island in the Arab-Persian Gulf subsequent to the oriental expeditions of Alexander the Great.     

New regression formula to estimate the whole population for recapture-addicted small mammals

We have devised a census formula of curvilinear regression suitable for capture-recapture data of recapture-addicted populations of the Japanese field vole (Microtus montebelli) obtained under a grid-plan with single-catch traps in order to estimate the whole population. The equation is founded on the assumption that the trappable population on the initial day is increased in way of an exponential curve until it reaches to the whole during one trapping period. The effect of trap-preoccupation by marked and multiple collisions is considered in the formula. As a result of its application to field data of the vole, it has turned out that the equation is required for the data gained under the trapping plan with trap spacing 10m, but not for those under the plan with spacing 5m, to estimate the whole. A convenient method of analysis of the formula is offered here, but we have been yet unable to introduce assymptotic variance of estimates.     

Pollen analysis of the contents of excavated vessels—direct archaeobotanical evidence of beverages

Direct evidence of mead and wine by pollen analysis is possible under certain circumstances which have prevented the decomposition of the original pollen content of vessels from archaeological contexts. This is shown here by two examples. The first, which concerns a Bronze bowl from a rich woman's grave of the late Hallstatt Period at Niedererlbach, Bavaria, must have contained mead as is indicated by the pollen, preserved by copper salts. The results are similar to those from Glauberg, Hochdorf and Heuneburg. The second example comes from Coptic wine amphorae of the early medieval period from Šaruna, Middle Egypt. Pollen, as remains of the former contents, had been preserved by the absolute dryness of the climate. Vitis pollen persists on the grape's surface and it is also detectable in the finished wine when it has been prepared without using modern vinification technology, as shown by experiments. In some samples a sweetening of the wine or an enrichment of the must by honey is evident. These honeys were not mixed like the Celtic honeys in central Europe were but were well-made Brassicaceae yield honeys which indicate a highly developed bee-keeping culture; since they were collected by wild bees they represent the bees' activity over a complete growing season.     

The dynamics of outbreaks: Further simulation experiments with the western tent caterpillar

A stochastic model of western tent-caterpillar populations on southern Vancouver Island was used to assess conditions leading to outbreaks. Three qualitatively different populations-declining, minimal, and recovering-were exposed to six-year climatic sequences incorporating various combinations of good, bad, and mediocre spring weather. Starting populations were either distributed randomly or concentrated in and around small-, medium-, or large refuges. The results showed that virtually any type of population could temporarily increase in numbers during two highly favorable springs. Only a very few vigorous populations, however, could sustain the momentum required to surge to outbreak proportions. No low-quality population could do so. And even vigorous populations could not achieve outbreak status unless they were initially concentrated in a sufficiently large refuge that was close enough to potentially suitable habitats to permit rapid immigration into such places as soon as their local climates improved. The concept of “climatic release” of insect populations is discussed in the light of these findings. The results demonstrate that climatic release is inextricably linked with a population's qualitative profile and spatial distribution.