2.1.4. Adults

Adult A. tumida beetles (Fig. 3d) are about 1/3 the size of a honey bee worker. They are oval-shaped and vary in size ranging from 5 to 7 mm in length and 3 to 4.5 mm in width. The adults’ bodies are broad and dorsoventral flattened. For a short period after emergence, they are coloured reddish-brown (Fig. 3c), but during maturation they darken to dark brown or even black (Fig. 3d). The head, thorax and abdomen are well separated. Their elytra are short, so that a few segments of their abdomens are visible, and their antennae are distinctively club shaped. The entire body is covered with short, fine hair.

Note: Caution must be taken not to confuse SHB with closely related Nitidulidae beetles. This is especially true for Cychramus luteus, which might be easily confused with not fully mature adult SHBs (Neumann and Ritter, 2004, Fig. 4). In cases of doubt, species status should be confirmed based on definitive morphological characteristics (e.g. shape of ovipositor and antennae, coloration, shape of pronotum, length of elytra, and other defined attributes, Freude et al., 1967). The following SHB characteristics are most useful to distinguish them from other nitidulids in the field:

Broadened ends of club shaped antennae are as long as wide

Short wing cases: end of abdomen is visible

Spiky edges on the lateral margins of the pronotum.

Fig. 4. Adult beetles of the family Nitidulidae, which are associated with honey bee colonies: a. Aethina tumida ready to emerge from the pupation chamber. Photo: Anna Röttger; b. Cychramus luteus. Photo: Frank Koehler.