Cold hardiness of some Alpine CollembolaBLOCK, WILLIAM; ZETTEL, JÜRG
doi: 10.1111/j.1365-2311.1980.tb01118.xpmid: N/A
Abstract.
1
Individual supercooling points ranged from ‐2 to ‐44°C for six species of springtails, five species from the Swiss Alps and one from lowland Britain. Individuals of Isotomurus alticola (Carl) and Isotoma viridis Bourlet without gut contents had substantially lower supercooling points than those containing food material.
2
Juveniles were more cold resistant than adults in both I.alticola and Isotoma hiemalis Schött, both with respect to supercooling point and to their survival at prolonged subzero temperatures.
3
Temperature and acclimation time affected the degree of supercooling of four of the Alpine species especially I.hiemalis.
4
Duration of culture period had no consistent influence on the supercooling potential of all the species.
5
Tests for glycerol in the body fluids of the five Alpine springtails were negative, but the presence of a sugar, probably glucose, together with a five carbon polyhydric alcohol was indicated by chromatography.
A preliminary study of dispersal and survival of Anopheles culicifacies in relation to the possibility of inhibiting the spread of insecticide resistanceCURTIS, C. F.; RAWLINGS, P.
doi: 10.1111/j.1365-2311.1980.tb01119.xpmid: N/A
Abstract.
1
Blood‐fed Anopheles culicifacies were collected in a cow‐baited hut, marked with fluorescent powder and released in the same hut. Captured mosquitoes were checked for the presence of marks from the previous day's releases. These checks were carried out on those captured in the release hut and in three similar huts at distances of up to 500 m away.
2
By dividing the percentage found to be marked in the outlying huts by the percentage marked found on the same day in the release hut, estimates were made of the extent of ‘overlap’ between the populations sampled by the different huts.
3
Evidence from the rate of build‐up in the percentage marked, from the daily loss rate when a ‘pulse’ of a different colour mark was used, and from the parity rate, gave information on mosquito survival and the interval between marking and recapture. This was notably high in view of earlier field work on the same species in India and of the fact that all houses on the site of the present experiment had been sprayed with malathion.
A population study in Jamaica on adult Sceliphron assimile (Dahlbom) (Hymenoptera: Sphecidae)FREEMAN, B. E.
doi: 10.1111/j.1365-2311.1980.tb01120.xpmid: N/A
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.
The effects of prey density on survival and growth of damselfly larvaeLAWTON, J. H.; THOMPSON, B.; THOMPSON, D. J.
doi: 10.1111/j.1365-2311.1980.tb01122.xpmid: N/A
Abstract.
1
Instar 10, 11 and 12 Ischnura larvae were maintained throughout the instar on a constant food supply (Daphnia magna of a standard size).
2
A very narrow range of prey availability separated cohorts in which all the larvae successfully moulted to the next instar, from those in which all the larvae died (less than one Daphnia per day in the case of instar 10).
3
Larvae were able to survive long periods without food at 16°C.
4
Prey availability had a marked effect on development rates, which continued to increase at prey densities well in excess of 100% survival by the larvae.
5
The data on Ischnura survival and development rates are compared with previously published general models of these two components of the predators' rate of increase.
6
We conclude that starvation is very unlikely to be a significant cause of mortality in the field for Ischnura (or indeed most other Odonata larvae), but that prey availability undoubtedly influences development rates. Natural selection should therefore favour larvae that forage optimally to minimize development times.
The effect of nectar abundance on foraging patterns of bumble beesMORSE, DOUGLASS H.
doi: 10.1111/j.1365-2311.1980.tb01123.xpmid: N/A
Abstract.
1
Bumble bees (Bombus spp.) fed more on previously screened, nectar‐rich plots of cow vetch (Vicia cracca) and white clover (Trifolium repens), and remained longer on inflorescences there, than on continually‐exploited plots of these flowers. No significant differences between previously screened and continually available plots occurred in the number of individuals visiting these two areas, the number of inflorescences per visit, the number of florets visited per inflorescence, and the percentage of inflorescences rejected.
2
Individual bees were analysed in greater detail. They visited more inflorescences and spent longer times on cow vetch in the previously‐screened plots, whether moving from previously‐screened to continually available areas, or vice versa. On white clover the same pattern held for bees moving from previously screened to continually available plots, but not for those moving from continually available to previously‐screened areas.
The distribution and abundance of the British fungal‐breeding DrosophilaSHORROCKS, B.; CHARLESWORTH, P.
doi: 10.1111/j.1365-2311.1980.tb01124.xpmid: N/A
Abstract.
1
The distribution and abundance of five Drosophila species breeding in fungi are examined by attracting adult flies to baited traps and collecting fungal fruit bodies containing the larval stages.
2
Changes in species frequency follow a temporal (seasonal and yearly), rather than a spatial (between and within woods) pattern.
3
There is a regular diurnal pattern of activity in D.subobscura but not in D.phalerata. Temperature, light intensity, humidity and wind speed have no effect upon the daily activity of D.phalerata. Only temperature affects the activity of D.subobscura.
4
Out of 125 species of fungi collected, only forty‐eight species produced Drosophila. However, the flies are even more selective, since only five species of fungi (Phallus impudicus, Polyporus squamosus, Amanita rubescens, Pluteus cervinus and Lactarius quietus) produce 80% of all Drosophila reared.
5
The commonest species, D.phalerata, has two or three generations per year with a winter diapause. An outline of the yearly life cycle is given, with the major breeding sites for each generation indicated.
6
Measures of niche overlap calculated from the data on individual fruit bodies are very low, suggesting that the five species are effectively isolated during the larval period. This ecological isolation is achieved by a summation of several niche dimensions, woodlands, seasons, fungal species, and individual fruiting body differences.