The Lords of Carrion

Perhaps the best way to demonstrate how marvel can be found throughout the natural world is to look at one particular species of animal that has throughout history been a symbol of pestilence, across the globe. It is seen by many as a species which spoils foods, spreads diseases and eats the dead. On top of this its habit of feeding on its own vomit hardly endears it any further, with its long list of adversaries. I introduce to you the bluebottle, the true lords of carrion.

Female Calliphora vicina

But are bluebottles simply misunderstood? Having recently taken the dive and bought a macro-lens, I have had chance to take a closer look at the intricacies of these unpopular but interesting creatures. Bluebottles belong to the Calliphoridae family of flies which also includes greenbottles. In winter it is relatively easy to find adult Calliphora vicina basking on tree trunks and walls, in many cases a spell of warm weather has caused the animal to come out of diapause. This multi-generation species is likely to overwinter in whatever life stage (larvae, pupae, oradult) it is in with the onset of winter. The use of diapause for overwintering in this species shows a north/south divide, with southern populations tending not to go into hibernation.

The association of carrion and bluebottles is well known but perhaps the efficiency and importance of this relationship is not. Bluebottles are capable of finding a carcase over 6km away, which is quite impressive given their size. Carcases are detected by odour, with the antenna (see below) and have a preference for slightly decayed flesh, of larger animals in full sunlight. They do not necessarily choose potent smelling carcases like fish and prefer mammals and birds. In fact carcases are mainly used as a place to lay eggs in which maggots can develop. This is an important characteristic of the species, without it we would be knee deep in dead bodies and disease, which the flies do a very good job of removing.

Female Calliphora vicina

Adults feed on sugar rich foods for energy like aphid honeydew and more familiarly foods like jam and chocolate, they are undoubtedly important pollinators too, feeding on nectar. The other food eaten is protein, especially so in females (for egg development),  in the form of pollen, dung and carrion. In the photo above the intricate feeding apparatus can be seen (at the base of the head). This consists of a proboscis evolved for vomiting and lapping.  This has lead to the curious habit of vomiting stomach acid onto the food, to dissolve it externally, before feeding on it. This liquefied food passes up two channels through two broad lobes (seen at the base of the head, eitherside of the hair proboscis) into the mouth. So the whole vomiting behaviour have evolved because the bluebottle cannot chew its food.  

Certainly a charismatic species group and one who's value is perhaps unappreciated. A group which will hopefully be cropping up on here time for time.