Hiromi Fukuda

Life tables for worker honeybees

Life tables for worker honeybees covering all life span, and those for adults, were prepared for three seasonal cohorts,June bees, July bees andwintering bees. Survivorship curves forJune andJuly bees show a convex type being exceptional for insects, with relatively high mortality at egg and feeding larval stages and at later adult stage after most bees became potential foragers. Adult longevity greatly lengthens inWinteriing bees and survivorship curve drops approximately with the same rate. A remarkable similarity of survivorship curves for men and honeybees was demonstrated, apparently due to highly developed social care in both. Some comments were given on mortality factors. The importance of life tables for population researches was shown by applying our result to the population growth curve made byBodenheimer, based upon the data byNolan. At the asymptote of the uncorrected curve, the ratio of total population estimated by uncorrected curve to that by corrected curve reaches about 3∶2.

Worker brood survival in honeybees

The brood survival in honeybee workers was measured in order to obtain the data basic to the preparation of life tables. Under normal condition, that is, at the center of brood area, the survival is high. The survival/stage function runs 100.0 eggs, 94.2 unsealed brood (=feeding larvae), 86.4 sealed brood (=post-feeding larvae and pupae) and 85.1 adults. The total duration of immature stages is 20 days in 87.1%, 21 days in 8.3% and 19 days or more than 22 days in the residual fraction of successfully emerging workers. The survival remarkably decreases at peripheral areas within the hive. Various factors affecting the brood survival are discussed and the importance of a dense worker cover on the brood area is stressed in relation to the maintenance of thermal conditions optimal to the brood. The occurrence of one factor, which is not expected in solitary animals, the self-control of population by egg eating, is pointed out.

The relationship between work efficiency and population size in a honeybee colony

The honeybee colony can be regarded as an ideal model to study the energy transfer process through biosystems by its simple energy inand output system. Energy input into the colony entirely depends on nectar and pollen brought by foragers, and output from the colonF is mainJy by excretion, respiration and death. The main energy pathway through a colony in active season is schematically presented in Fig. 1 which was developed by the author and further improved by P r o f . S~. F. SAI~AGA~I. Relative amount of energy input per day is given by food (nectar and pollen) brought by foragers on a given day, which is estimated by the foraging efficiency (= mean crop or pollen load weight • mean daily number of foragers). The food is consumed by immatures (mainly unsealed brood) and adult themselves and the surplus is deposited in the combs, which is particular to the honeybee

Life of a Japanese eusocial halictine bee Lasioglossum duplex, out of brood rearing season (Hymenoptera Halictidae).

SummaryFollowing the previous studies on the life of a Japanese eusocial halictine bee,Lasioglossum (Evylæus duplex Dalla Torre), in the brood rearing season, some observations on the life in other seasons are presented in order to complete the description of annual cycle. The results are summarized as follows: 1) Departures of autumn sexuals from a nest indicate proterandric emergence. 2) Abundant males but few prehibernating females are collected on flowers in spite of only a slight numerical predominance of males among pupae. 3) Few males return to nests and all die before winter. 4) Natural mating was observed only once, at the nest site. In confinement, mating is initiated by flying males, which land on females. Females are indifferent or even try to dislodge males so that only ca. 5% of males attempts lead to mating, which lasts 4∼5 sec., with an akinetic posture of males. 5) Except for a few instances of excavation of new burrows, most hibernating females are found within old nests, each closing herself within a blind chamber. 6) Some nests include few hibernating females in spite of many summer cells, while there are nests with too numerous females, indicating invasions from alien nests. 7) From experiments in two years, survival during winter is provisionally estimated as 57.3%. 8) There is no definite relation between body size and winter survival. 9) Crop weight of hibernating females decreases distinctly by spring. Winter weight loss approximately equals to 14∼15 % of the autumn body weight. Females do not eat pollen before wintering. 10) Many old mothers enter hibernation and some of them survive to their second spring. 11) Spring nest foundation is partly by excavation of new burrows from the surface by females from hibernacula. But nest founding through subterranean dispersal from hibernacula produces a much higher portion of the new nests.ZusammenfassungAnschliessend an den früheren Studien über das Leben einer japanischen eusozialen Furchenbiene,Lasioglossum (Evylæus) duplex Dalla Torre, während Brutpflegezeit, werden einige Beobachtungen in anderen Jahreszeiten dargestellt, um die Beschreibung des Lebenszyklus zu ergänzen. Die Ergebnisse werden zusammengefasst wie folgt: 1) Ausgänge der herbstlichen Geschlechtstiere aus einem Nest zeigt eine Tendenz zur proterandrischen Ausschlüpfung. 2) Zahlreiche Männchen aber wenige neuausgeschlüpfte Weibchen werden auf Herbstblüten gefangen, obwohl das Verhältnis von Männchen in Bruten nur ein wenig überlegend ist. 3) Heimkehr der einmal ausgehenden Männchen scheint ausnahmsweise und alle Männchen sterben vor Winter. 4) Natürliche Begattung wurde nur einmal an Neststätte beobachtet. Unter Gefängnis wird die Begattung eingeleitet von fliegenden Männchen, die auf meistens ruhige Weibchen landen. Die Weibchen sind meistenfalls teilnahmlos oder sogar ablehmend, so dass die Begattung, die von einer akinetischen Körperstellung von Männchen charakterisiert ist, nur in ca. 5% der Gesamtfälle gelungen ist. 5) Abgesehen von wenigen neuausgegrabten Hibernakulen, bleiben überwinternde Weibchen meistens in Sommerhestern, und zwar jedes sich in einer geschlossenen Kammer zur Ruhe sitzend. 6) Gewisse Nester enthalten nur wenige Weibchen trotz dem Vorkommen mancher Sommerzellen, während einige andere Nester manche Weibchen im Vergleich zur Zellenzahl, was die Invasion gewisser Weibchen in die fremden Nester andeutet. 7) Aus zweijährigen Versuchen wird das Verhältnis des Winterüberlebens vorläufig als 57.3% geschätzt. 8) Es gibt keine deutliche Korrelation zwischen Körpergrösse und Winterüberleben. 9) Magengewicht nimmt nach Ueberwinterung deutlich ab. Winterfutterauszehrung wird als ca. 14∼15 % vom herbstlichen Körpergewicht gerechnet. Kein Weibchen nimmt den Pollen vor Ueberwinterung ein. 10) Manche alte Mütter gehen in Ueberwinterung und z. Teil kann sogar bis zum nächsten Frühjahr überleben. 11) Frühjährige Nester werden, z. Teil von den Weibchen, die einmal Hibernakulen verliessen, durch Neugraben an der Erdoberfläche, aber meistens durch unterirdische Abspaltung der gemeinsam überwinternden Weibchen gruppe gegründet.

Factors Governing the Spatial Distribution of Adult Drone Honeybees in the Hive

SummaryIn summer, younger Apis mellifera drones in a normal frame hive were concentrated in the centre, and older drones were more on the peripheral combs. In autumn, and as winter approached, the older drones moved to the central area and then migrated with the workers to the upper storeys of the hive. In a single-comb observation hive young drones were near the centre and older drones on the outer parts, except that the lowest part of the comb was avoided (less so when the worker population was higher). Five hypotheses to explain the observations are discussed, and it is concluded that age-specific temperature preference is the factor most consistent with all the results obtained.Drone destruction by workers was not observed in the autumn: a possible reason was the abnormally high number of young drones present, and the abundance of the honey stores.

Entomological and ecological surveys on Mt. Usu in 1984 VI: Faunal make-up and ecological distribution of springtails (Collembola) on Volcano Usu

A survey of springtails was conducted in 1984 on Volcano Usu which suffered damage to its ecosystem from eruptions in 1977 and 1978. The summit area, almost completely deforested by the eruptions, was still inhabited by many forest species such asDesoria notabilis, Willowsia sp. 2,Pseudachorutes sp. 2,Isotoma sp. 4,Tullbergia yosii, Onychiurus sp. 1,Entomobrya sp. 2,Isotomiella minor, Proisotoma sp. 2,Xenylla sp.,Neanura frigida, etc. These species preferred standing or fallen dead trees, mosses, bark chips, former topsoils and soil around the root of plants. The fauna in the summit area was most similar to that of coniferous or broad-leaved forests surveyed on the foot of the mountain. This suggests that the 1977–78 eruptions did not exterminate these springtail species which probably survived on the standing trees or in the former topsoil.