Yasuo Maeta

Some presumably presocial habits of JapaneseCeratina bees, with notes on various social types in Hymenoptera

SummarySome Japanese species ofCeratina bees exhibit habits which seem to be precursors to social life, namely: 1) Removal of larval feces by the mother, accompanied by destruction and reconstruction of cell partitions. 2) Transport of immatures within nest. 3) Guarding by the mother at the nest entrance, which is effective in protecting the immatures from parasites. 4) Association of the mother and juvenile adults in autumn, with pollen intake by juveniles from the mother, and 5) Prolonged life span of some females, followed by brood rearing in the second year.Three nests ofC. japonica and four ofC. iwatai, each containing two or more females in brood rearing condition are recorded. The relations among co-habiting females are variable: semisocial, delayedly eusocial,eosocial (nom. nov.) and quasisocial. The significance of these findings are discussed in connection with social evolution and various social types found or assumed in Hymenoptera.ZusammenfassungEinige japanischen Bienarten der GattungCeratina zeigen folgende Lebensgewohnheiten die als evolutionäre Vorstufen zur Staatsbildung aufgefasst werden können. 1) Das Weibchen entfernt den Kot seiner Brut, wobei es die Scheidewände zwischen den Brutzellen durchbricht und wieder aufbaut. 2) Larven werden innerhalb des Nestes transportiert. 3) Das Weibchen bewacht den Nesteingang und schützt dabei die Brut vor Parasiten. 4) Mutter und Jungbienen bewohnen im Herbst gemeinsam das Nest wobei die Jungbienen von ihrer Mutter Pollen übernehmen. 5) Die Lebensdauer einiger Weibchen ist soweit verlängert, dass eine weitere Brutaufzucht im zweiten Jahr möglich ist.Ueber drei Nester vonC. japonica und vier vonC. iwatai wird berichtet, die während einer Brutperiode je zwei oder mehr Weibchen enthielten. Die Form der Wechselbeziehungen zwischen den zusammenlebenden Weibchen variiert von semisozial, aufgeschoben eusozial, biseosozial (nom. nov.) und quasisozial. Die Bedeutung dieser Befunde in Bezug auf die Evolution der Insektensozietäten wird erörtert unter Bezug auf die verschiedenen aktuellen und hypothetischen Sozialtypen der Hymenopteren.

Pollination of strawberry by the stingless bee,Trigona minangkabau, and the honey bee,Apis mellifera: An experimental study of fertilization efficiency

To know basic information about the stingless bee,Trigona minangkabau, and the European honey bee,Apis mellifera, as pollinator of strawberry, we set three greenhouse areas: the honey bee introduced area, the stingless bee introduced area and the control area. Foraging and pollination efficiencies of the two bee species were studied comparatively. During the experimental period (10 days), the stingless bee foraged well and the nest weight did not change, though the honey bee often foraged inefficiently and the nest weight decreased by 2 kg. The average nectar volume of a flower was lower in the honey bee area (0.02 μl) and nearly the same in the other two areas (0.1 μl). We make a numerical model to describe pollination and fertilization process. This model shows that one visit of the honey bee pollinated 11% of achenes and one visit of the stingless bee did 4.7% on average and that 11 visits of the honey bee or 30 visits of the stingless bee are required per flower to attain normal berry (fertilization rate, 87%). In this study, the rate of deformed berries in the stingless bee area (73%) was lower than that of the control area (90%), but higher than that of the honey bee area (51%). From our numerical model, we conclude the stingless bee could pollinate strawberry as well as the honey bee if we introduced 1.8 times of bees used in this experiment.

A Phylogenetic Analysis of Nesting Behavior in the Genus Osmia (Hymenoptera: Megachilidae)

Abstract Cladistic analysis is used to study the evolution of 29 biological characters related to nesting behavior, nest provisioning, oviposition, cocoon spinning, defecation, and life cycle (nest characters) in 11 species of Osmia bees (Hymenoptera: Megachilidae) and two outgroup genera. A molecular phylogeny based on 38 allozyme loci-as-characters and a combined character phylogeny are produced to compare with the nest character phylogeny. All phylogenetic trees support the monophyly of the genus Osmia and the subgenus Osmia (Osmia) with Osmia ribifloris Cockerell basal to the other species in this subgenus. The subgenus Helicosmia (=Chalcosmia) is resolved as a sister clade to O. (Osmia) in the molecular tree and as sister to the subgenus Cephalosmia in the nest character and combined trees. Incomplete biological information from additional species of all three subgenera is provided to support the consistency of nest characters at the subgeneric level and their use in the establishment of subgeneric phylogenies in the family Megachilidae.

Geographical variation of sociality and size-linked color patterns in Lasioglossum (Evylaeus) apristum (Vachal) in Japan (Hymenoptera, Halictidae)

Summary:Lasioglossum (Evylaeus) apristum was studied at 2 localities in Japan. By rearing bees in a greenhouse in Matsue (lat. 35° 29′, alt. 170 m), south-western Japan, it was revealed that the bees had an eusocial life cycle with 2 distinctly discrete brood rearing periods, i.e., a solitary phase in spring and an eusocial phase in summer. The life cycle and sociality were of the same pattern as those at Mt. Daisen (lat. 35° 22′, alt. 800-1000 m), 50 km from Matsue, where females reared in the greenhouse were collected. On the other hand, in Sapporo (lat. 43° 03′, alt. 20 m), northern Japan, the solitary life cycle was suggested by a phenological survey. The effective accumulative temperature was compared for each locality, as an index of local thermal condition. The accumulative value at Mt. Daisen and Sapporo did not differ. The fact suggests that short flying season at high latitudes, such as in Sapporo does not induce the solitary life cycle in L. apristum. Approximately 39% of workers in the eusocial colonies at Matsue had well-developed ovaries, suggesting that they were possible egg-layers. No clear proof of the allocation of foraging in relation to the size and age of workers was obtained. Uninseminated, small, worker-sized females were also produced, together with new queens at autumn at Mt. Daisen. Hibernation by these uninseminated females was suggested. The size-linked color patterns of the metasoma were recognized among the pre-hibernating females at both localities.

Host body size as a factor determining the egg complement of Strepsiptera, an insect parasite

Abstract The egg complement (total number of eggs produced by a single female) differs greatly among the species of Strepsiptera. The maximum is found in Stichotrema dallatorreanum (750,000 eggs), and the minimum in Triozocera minor (984 eggs). Based on the egg complement of 31 species in 11 genera, the following conclusions were drawn: (1) The egg complement is generally smaller in those species whose hosts gregariously cohabit in a very limited area, or are distinct flower-visitors, compared with those whose hosts display the above two traits weakly; (2) The egg complement is determined by the size of the maternal body. The size of female strepsipterans is reduced when they parasitize smaller host such as males and workers, as compared with those that parasitize larger host such as females and queens; likewise, the size of the strepsipterans becomes larger on increase in size of hosts, showing that their egg complements are principally determined by the size of host species; (3) The increase in the egg complement is compensated for by the reduction in egg size. The relative egg size (length of the firstinstar larva/length of maternal body) is conspicuously reduced according to an increase in the size of the female strepsipterans.

Seasonal changes in ovarian state in a eusocial halictine bee,Lasioglossum duplex, based on stages of the oldest oocytes in each ovariole (Hymenoptera: Halictidae)

The changes in ovarian activity in the life cycle of the eusocial halictine beeLasioglossum (Evylaeus) duplex (Dalla Torre) was studied in both queens and workers by examining the stages of the terminal follicle in each of the six ovarioles. By this method, ovarian activities of both queens and workers were more quantitatively determined than by observation of gross ovarian features as usually conducted. Queen ovaries clearly exhibited two active periods, corresponding to the spring solitary phase and the summer eusocial phase, with distinctly greater activity in the latter. In ovaries of overwintering queens oosorption of young follicle was observed. Worker ovaries were found more active in orphan than in queenright colonies. The order of ovarian activity obtained from pooled data, summer queens>spring queens>orphan workers>queenright workers, was also recognized by comparison of individual females.

Discovery of wood nesting by a subterranean halictine bee, Lasioglossum (Evylaeus ) vulsum (Hymenoptera: Halictidae): Nesting plasticity of halictine bees

An unusual nesting substrate of a subterranean halictine bee, Lasioglossum (Evylaeus) vulsum (Vachal), was found at Mt Ishizuchi‐san, Ehime, Japan. Two nests were obtained from a decaying log in a display sign for a local restaurant. Brood cells, forming a cell cluster, were constructed in a wood hollow with rotted wood fibers pressed together. Nests in the decaying log show the same structural elements as those made in soil. This is the first report of wood nesting by subterranean halictine bees belonging to the subgenus Evylaeus.