viernes, 9 de febrero de 2007

Vespula germanica (Macho)

Dolichovespula sylvestris (Avispa arbórea)
Camara Kodak DX6490 con Raynox DCR250. Flash Difusor. F8 -1/350

Identificado por Camille Thirion

Phylum: Arthropoda
Subphylum: Mandibulata
Clase: Insecta
Subclase: Holometabola
Orden: Hymenoptera
Suborden: Apocrita
Infraorden: Aculeata
Superfamilia: Vespoidea
Familia: Vespidae
Subfamilia: Vespinae

Las avispas Vespula germánica son insectos sociales y organizados. Presentan en su nido una reina, encargada de la reproducción; obreras que son responsables de alimentar las larvas, y machos que aparecen a fines del verano y cuya única función es fecundar a las nuevas reinas que invernarán hasta la próxima primavera. La colonia alcanza su máximo tamaño a fines del verano, época en la cual las obreras buscan alimento rico en proteínas para alimentar a los futuros machos y reinas.
La reina de la avispa chaqueta amarilla carnívora tiene un tamaño de 1 a 2 centímetros, con el abdomen abultado, poca cintura, antenas negras y sólo se verá volar a inicios de primavera. Las obreras son las de menor tamaño y los machos el tamaño intermedio.
Los nidos en general son subterráneos o aéreos, siempre en cavidades preformadas.
El radio de acción de las obreras de vespula germanica es de unos 300 metros del nido.
Puede consumir cualquier alimento: polen, fruta, carne, otros insectos. También puede atacar al hombre y animales como vacas, perros, gallinas y aves.
Vespula germanica desarrolla sus nidos dentro de cavidades preformadas tanto en el suelo como en el aire, en cambio Polistes spp desarrolla sus nidos en altura al aire libre, generalmente bajo aleros o techos o en árboles y con un solo panal .
Morfologicamente lo mas diferenciador es la apariencia mas estilizada de las avispas del genero Polistes, respecto a la chaqueta amarilla carnivora, es decir patas mas largas y abdomen mas marcado.

The German wasp, Vespula germanica is a wasp found in much of the Northern Hemisphere, and introduced to Australia and New Zealand. German wasps are part of the Vespidae family and sometimes mistakenly referred to as a paper wasp because it builds a grey paper nest, although strictly speaking Paper wasps are part of the Polistinae subfamily. It is more commonly known in North America as a yellowjacket.
The German wasp is about ½ inch (13 mm) long, and has typical wasp colours of black and yellow. It is very similar to the common wasp (Vespula vulgaris), but seen head on, its face has three tiny black dots, thought to be horizon detectors. German wasps also have black dots on their abdomen, while the common wasp's analogous markings are conjoint with the black rings above them, forming a different pattern.
The nest is made from chewed plant fibres, mixed with saliva. They are generally found close to or in the ground, rather than higher up on bushes and trees like hornets. It has open cells and a petiole attaching the nest to the substrate. The wasps produce a chemical which repels ants and secrete it around the base of this petiole in order to avoid ant predation.
A solitary female queen starts the nest, building 20-30 cells before initial egg-laying. This phase begins in spring, depending on climatic conditions. She fashions a petiole and produce a single cell at the end of it. Six further cells are then added around this to produce the characteristic hexagonal shape of the nest cells.
Once the larvae have hatched as workers, they take up most of the colony’s foraging, brood care and nest maintenance. A finished nest may be 20-30 cm across and contain 3,000 individuals.
Each wasp colony includes one queen and a number of sterile workers. Colonies usually last only one year, all but the queen dying at the onset of winter. However, in mild climates such as New Zealand, around 10% of the colonies survive the winter. New queens and males (drones) are produced towards the end of the summer, and after mating, the queen overwinters in a crack or other sheltered location.
This common and widespread wasp collects insects including caterpillars to feed to its larvae, and is therefore generally beneficial (unless you are a caterpillar). The adults feed on nectar and sweet fruit, and are also attracted to human food and food waste, particularly sodas and meats.
The nests are subject to predation by the Honey Buzzard, which excavates them to obtain the larva. The hoverfly Volucella pellucens and some of its relatives lay their eggs in the wasp nest, and the larva feeds on the wasp’s young.

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