Bellardia species Bellardia sp
In common English members of the genus Bellardia are refered to as Emerald Bottles. Yet they differ considerably from the usual Green Bottles. First of all only their abdomen is greenish and shiny. The thorax is dark grey with some lighter grey or black lines, common in many other flies as well. The green on the abdomen also is less striking, for the abdomen is quite pruinose, even more so in one place then in another. In some animals the green parts may even be almost invisible. In Britain there are four or five species within this genus, in neighboring Holland and Belgium there are five or six species. The species are very hard to tell apart. Sometimes the difference is in just one particular hair, which grows upwards in one species and downwards in another. Little details like that are very hard to capture in photographs. It is preferred to tell the species apart by examining the genitals.
The larvae of the Bellardia species all are parasitic to earthworms. The adults feed on nectar and pollen. The females of the species all are viviparous, which means that the eggs hatch inside the female animal. The new born larvae are then dropped on a suitable host by mother. The larva immediately enters the body of the earthworm and starts eating from the inside. Under good conditions the larva may eat an entire earthworm in just one weeks time and pupate. Larvae in the third instar stay within the left overs of the earthworm and overwinter.
Bellardia species are very common all over Britain, even though it is very hard to tell which species is more common. This is due to the fact that the species are so similar. This means identification often halts at the genus level.