FNZ 57 - Apoidea (Insecta: Hymenoptera) - Life cycles
Donovan, BJ 2007. Apoidea (Insecta: Hymenoptera). Fauna of New Zealand 57, 295 pages.
(
ISSN 0111-5383 (print),
;
no.
57.
ISBN 978-0-478-09389-6 (print),
).
Published 07 Sep 2007
ZooBank: http://zoobank.org/References/B2070E05-13B6-4CBF-9A0A-0ACE40FA4796
Life cycles
All bees in New Zealand consume pollen and nectar, or processed materials derived from pollen and nectar. Pollen is the primary source of protein, and nectar is the source of sugars. Honeydew, which is a sugary secretion of a number of sap-feeding insects, may also be consumed by some bees. All collection of pollen and nectar is undertaken by female bees, or in the case of social species, worker bees, which are genetically female. Male bees spend all their time seeking to mate, feeding or being fed, and resting. They play no part in foraging for the nest, nest construction, tending brood, or nest defence. However, male Anthidium manicatum drive other flower-visiting insects from patches of bloom, which makes more pollen and nectar available for collection by female A. manicatum. Although the life cycle of all non-parasitic bees is broadly similar because of the reliance on pollen and nectar, there are wide differences both within and between species in the different families.
All bees construct a nest within which their young are raised. For solitary species and native, partly social species, a nest consists of a blind tunnel that female bees excavate in soil, or a pre-existing, blind tunnel in plant material such as dead branches and stems. The introduced, partly social bumble bees, and the social honey bee occupy much larger spaces such as abandoned rodent nests, or large hollow trees and sometimes cavities in cliffs. All bee nests contain cells, within which larvae are raised, and for bumble bees and the honey bee, food surplus to immediate requirements is stored. The cells of solitary bees, and partly social native bees, are individual chambers that are excavated in the soil either terminally from tunnels, or off the sides of tunnels, or are built in tunnels in plant material where they lie end-to-end in the tunnel, or for Anthidium manicatum, are rather jumbled in a mass of plant fibres in larger blind cavities. For bumble bees and the honey bee, the cells are separate but adjacent (bumble bees), or are completely integrated into combs (honey bee).
Solitary and partly social native bees mass-provision their cells with all the pollen and nectar their larvae will need, an egg is deposited on the food, and the cell is sealed, so there is no contact with the remainder of the nest until the new bee emerges. Bumble bees and the honey bee, however, feed their larvae progressively, so the cells are not sealed until the larvae have reached full size.
Colletidae
The Colletidae are often considered to be one of the most primitive families of bees (Michener 2000). The life cycle is annual, with females and males emerging in spring/early summer, nest construction occurring until mid-late summer, adults dying by autumn, and prepupae surviving the autumn and winter.
Female Colletinae range in size from about 1/3 the size of a worker honey bee, to about as large. They are quite stout and densely covered in vestiture, and pollen is carried externally primarily in scopae on the metalegs. Males are generally a little smaller and slimmer than females of the same species. Females excavate nesting tunnels and cells in bare or near-bare ground, such as cliff faces, silt in river beds, and ocean beaches from beyond high tide level to the line of dense vegetation. The substrate must be dry and free draining, although nests in river beds and near the high tide level on beaches can survive inundation for at least several hours. Tunnels that have been examined have always been at least partly filled with loose soil, through which bees have to dig to exit and return to a cell. In flat ground tunnels always slope well away from the vertical. The cells are lined with cellophane-like material, and occur singly at the end of individual tunnels. During the period of adult nesting activity, nest entrances are frequently surrounded by a tumulus of excavated soil particles up to about 10 mm high and 30–40 mm across. Nests are usually aggregated, so hundreds or even thousands may occur within a few square metres, even though other areas of ground without nests appear similar or even identical to the occupied area.
Females forage primarily on native Asteraceae, Myrtaceae, and Fabaceae, with some bee species restricted to just a few species in one family. However, some species have adapted to introduced plants such as kiwifruit (Actinidiaceae), onions (Alliaceae), some Asteraceae, and many others, on which they are now found foraging in large numbers.
Female Hylaeinae carry pollen internally, and both sexes are relatively naked compared with Colletinae. The lack of vestiture makes many Hylaeinae appear rather slim, much like some sphecoid wasps, although Hyleoides concinna, which is quite stout, was first described as a vespid wasp. Adults range in size from just a few mm long to longer than a worker honey bee. Nests are constructed in hollow plant material, such as tunnels and cavities made and abandoned by other insects, and pith cavities. The tunnels are cleaned out and filled with cells with walls of a cellophane-like material which is painted on by the mother bee. As with Colletinae, there appears to be just one generation per year, with species surviving the winter as prepupae, although it seems new nests exposed to the sun may produce adult bees that same year. In addition to foraging on native flowering species, several species of Hylaeinae forage on introduced flowering species such as kiwifruit, Rosaceae, and others.
Little is known of Euryglossinae in New Zealand, but the life cycle is probably much like that of Hylaeinae. Adults have emerged from insect tunnels in kanuka (Kunzea ericoides), and have been captured on wood infested with the borer Anobium punctatum.
Halictidae
New Zealand Halictidae are all ground-nesters, so in this respect are similar to the Colletinae. However, the development of a form of social nesting and multivoltinism, at least in Lasioglossum sordidum, are major distinguishing features.
The Nomiinae are represented by the alkali bee Nomia melanderi, introduced as a specialist, manageable pollinator of lucerne seed crops. Females are about the size of worker honey bees and males are a little larger, and are readily distinguishable by the presence of 3–5 prominent transverse yellow/green bands on the metasomal terga. Females carry pollen in scopae on the tibiae of the metathoracic legs. Prepupae survive the winter in cells in moist soil, and adults begin emerging in early summer. After mating, females may renest in an old tunnel, or may excavate a new tunnel. Tunnels are made only in fine-grained soil that is moist from below right to the surface. The only soils of this type that occur naturally in New Zealand are saline, and so show salt at the surface in dry weather. Nests are aggregated, even where areas of suitable soils are extensive. In contrast to the sloping, partly filled tunnels of Colletinae, tunnels of N. melanderi are vertical or near-vertical, and are clear to the cells, which are 100–400 mm below the surface. The species is primarily univoltine, but there can be a small second generation late in summer when the summer has been hot. Females forage mainly on introduced legumes and composites.
The Halictinae are about 1/2–1/3 as long as worker honey bees, but appear much less stout. Pollen is carried primarily in scopae on the metathoracic legs, but also laterally in scopae on the propodeum. An outline of the life cycle is known for only one species, Lasioglossum sordidum, but that of other species is almost certainly similar. Fertilised females overwinter in nest tunnels in the ground. The first bees of the new season begin emerging soon after the soil starts warming, which can be as early as late winter, and several females may carry pollen into the same nest. It appears that females may renest in the tunnel within which they have overwintered, or they may initiate new nests. New females and males begin appearing by late spring. Nests are aggregated and, as with Colletinae, there can be many hundreds or thousands in a small area. Because of their long nesting period, Halictinae forage on a very wide range of flowering plant species both native and introduced.
Megachilidae
The red clover mason bee Osmia coerulescens was imported to be developed as a specialist, manageable pollinator for red clover seed crops, and the lucerne leafcutting bee Megachile rotundata similarly for lucerne seed crops.
Adults are about 2/3 the size of worker honey bees, and females carry pollen in a scopa on the ventral aspect of the metasoma. Both species nest in blind tunnels in plant material, which in nature are abandoned tunnels of insect larvae, pith cavities in twigs and stems, suitable cracks in dead tree trunks, and gaps between peeling bark and tree trunks. Cell partitions and the nest plug partitions of the red clover mason bee are made of chewed leaf material, whereas the lucerne leafcutting bee uses cut leaf pieces for its cells, and for the nest plug. The red clover mason bees overwinter as adults in cells, and the lucerne leafcutting bees overwinter as prepupae in cells. Adults begin emerging in late spring, and after mating, females clean out a suitable tunnel, and a series of cells is constructed end to end. As with the Hylaeinae, each cell is mass-provisioned. If a nest is constructed in early summer, a second generation of adults may emerge and renest in late summer, but cells made after early summer do not show emergence until the following season. The population of red clover mason bees is very small, and so far females have been observed foraging only on introduced legumes. Leafcutting bees forage primarily on introduced pasture legumes and composites, but some native legumes are also attractive.
Females of the very recently discovered adventive wool-carder bee, Anthidium manicatum, are a little larger than female red clover mason bees and lucerne leafcutting bees, but males range in size from just bigger than females to as large as small bumble bees. Based mainly on the species life cycle elswhere, in New Zealand there are likely to be 2 generations from spring to autumn, and females will probably forage primarily on flowers of some introduced plants. Pollen is carried in a scopa on the ventral aspect of the metasoma, and cells made within plant fibres are mass-provisioned. The only nest as yet known from New Zealand consisted of 5 cells and 30 cocoons in a golfball-sized mass of plant fibres in an irregular cavity in an aluminium window-frame.
Apidae
The 4 species of Bombini were imported to improve the pollination rates and thereby the seed yield of imported red clover, whereas the single species of Apini, the honey bee, was imported for honey production. All 5 species have 2 usually quite distinct female castes of queens and workers, in addition to males or drones. Female bumble bees and worker honey bees carry pollen in pollen ‘baskets’ or corbiculae on the metatibiae. The bumble bees are primitively eusocial, with from 1 to about a few hundred individuals living in specially constructed nests of irregularly arranged waxen cells, whereas the honey bee is highly eusocial, with many thousands of bees living intimately in precisely constructed waxen combs, each comprised of thousands of hexagonal cells.
Bombini are probably the bees that are most readily recognised by the bulk of people. All are from about honey bee size to several times larger, and are stout and densely hairy, with the vestiture arranged in black, yellow, orange-yellow, or lemon-yellow transverse bands, or black and yellow-green, and they fly with a loud buzz. Most fertilised queens of all 4 species pass the winter in small cavities excavated in the ground. Rising spring temperatures stimulate the queens to emerge, and after feeding following their long fast, they begin to search for a dry, sheltered cavity such as an abandoned mouse or rat nest, within which to begin constructing a nest. Queens carry pollen and nectar into a cavity, where over the next 4–5 weeks several dozen worker bees are raised. After a number of workers have emerged, the queen confines her duties to ovipositing, whereas the workers collect all food, tend the larvae, and defend the growing nest. Within about 2 months from the foundation of the colony, drones begin emerging, followed soon after by new queens. Mating occurs outdoors, after which new queens disperse, with some founding new colonies that same summer, and others entering hibernation for the winter. By early-mid summer colonies may number up to a couple of hundred workers, but after producing as many as 100 or more new queens, the old queen, the workers, and any straggling drones all die by late summer. Some queens, workers, and drones of at least 2 species may be on the wing throughout the winter, as the variable New Zealand climate can sometimes upset the nesting cycle.
Apini is represented by the honey bee, Apis mellifera. Colonies are perennial. During the winter they consist of one fertilised queen, and up to about 20,000 worker bees. By late spring/early summer, the worker population increases to 50–80,000, and several hundred to several thousand drones may also be present. Colonies reproduce by swarming, when up to several tens of thousands worker bees abandon the colony, accompanied by the old queen and a number of drones. They leave behind about half the workers and drones, all the developing brood, stores of honey and pollen, and up to several dozen new queens, which are developing in special queen cells. Sometimes secondary swarms will issue forth, each with a new, virgin queen and a diminishing number of workers and drones. Finally, one new queen leaves the hive alone, and after mating, returns to head the old colony.
Swarms seek out a new cavity such as a dry hollow tree, in which new honey combs will be constructed. Because adult bees survive the winter in an active state, large quantities of honey and pollen must be stored during summer so there is sufficient food available not only for the winter, but the early spring when inclement weather often limits foraging, and the numbers of larvae are increasing rapidly.
Honey bees possess a ‘language’ that allows the transference between workers of information in a symbolic form about the distance and direction of foraging resources from the colony, and potential nesting sites for a swarm.