Box-headed blood bee (Sphecodes monilicornis)
Box-headed blood bees (Sphecodes monilicornis) are medium to large sized black bees with blood-red abdomens. They are cleptoparasites of several Furrow bee species and females forcibly invade pre-stocked nest cells, destroy the resident egg or grub, and replace it with their own before resealing the cell.
Males are smaller than females, with slightly less red at the top of the abdomen. Without close inspection under a microscope, they can be difficult to distinguish from other male Blood bees, although they belong to a group which have flattened antennal segments.
Females are medium-sized black bees with blood-red abdomens. They can be distinguished from other similar Blood bees by their box-shaped heads, thinner bodies and the pale hairs on their hind legs. Their heads have distinctive punctures across the top behind the three ocelli (primitive eyes on top of a bee’s head in between the two main eyes).
Habitat, host and flower preferences
These bees are associated with open habitats, especially those containing good populations of their hosts. Hosts include the Orange-legged Furrow bee (Halictus rubicundus), the Common Furrow bee (Lasioglossum calceatum), the Bloomed Furrow bee (Lasioglossum albipes) and the Sharp-collared Furrow bee (Lasioglossum malachurum). They don’t have any specific preferred flower species, although will usually be seen on composite flowers or umbellifers.
Flight season & Distribution
Seen from March to September, with females appearing first and males emerging in July. Widely distributed across the UK and locally common in areas of southern England and Wales. Present in Scotland and Ireland, although much less common.
Despite the blood-red coloured abdomens which gives this group of bees their name, insects don’t actually have blood. Instead they have a blood-like bodily fluid known as hemolymph, which contains copper based proteins called hemocyanins that move oxygen around their bodies, rather than red blood cells. This apparently gives insect ‘blood’ more of a blue/greenish hue, however we don’t recommend trying to check this out for yourself!