Eristalis tenax

Order: Diptera
Family: Syrphidae
Genus: Eristalis
Species: E. tenax

Es una de las moscas de las flores más frencuentes en todo el mundo. Es prácticamente negra o de color azul muy oscuro, salvo las dos marcas anaranjadas sobre el abdomen, que le confieren su parecido con las abejas.
Tiene un tamaño mediano o grande. La cabeza es grande y luce una conspicua proyección frontal; las antenas tienen tres segmentos. Los ojos están más separados en las hembras que en los machos.
Se alimentan de néctar de diversas flores, sobre las que pueden permanecer en vuelo cernido.
Las larvas viven en aguas muy sucias, con muy poco oxígeno, ya que respiran a través de un tubo muy largo, implantado en el extremo posterior del abdomen, que emerge en la superficie. Esta particularidad anatómica les ha valido el nombre de "cresa de cola de rata".
Para pupar se esconden debajo de piedras en lugares secos. fuente:http://mediateca.educa.madrid.org/imagen/ver.php?id_imagen=vbydycz9jzinb6x6
Eristalis tenax is a European hoverfly, also known as the drone fly (or "dronefly"). It has been introduced into North America and is widely established there.
The larva of E. tenax, is a rat-tailed maggot. It lives in drainage ditches, pools around manure piles, sewage, and similar places containing water badly polluted with organic matter. The larva likely feeds on the abundant bacteria living in these places.
When fully grown the larva creeps out into drier habitats and seeks a suitable place to pupate. In doing so it sometimes enters buildings, especially barns and basements on farms. The pupa is 10-12 mm long, grey-brown, oval, and retains the long tail; it looks like a tiny mouse.
The adult fly that emerges from the pupa is harmless. It looks somewhat like a drone honey bee, and likely gains some degree of protection from this resemblance to a stinging insect. The adults are called drone flies because of this resemblance. They, like other hover flies, are common visitors to flowers, especially in late summer and autumn, and can be significant pollinators.
In its natural habitat, E. tenax is more of a curiosity than a problem, and the adults are beneficial pollinators. Drone flies have never been implicated as disease vectors and usually do not become a problem provided sewage and manure are not allowed to accumulate in pits, ponds, or streams.

La Azohia.Cartagena.06/2007