Social bee symbionts (Melittophiles) are considered scarce in nature (Kistner 1979). Even so, some arthropods have been observed to co-inhabit beehives (Neumann and Ritter 2004). These arthropods may be parasites, commensals, or mutualists, and range from mere invaders occasionally using a nest as shelter to invaders forming more intricate and evolutionarily significant relationships with their hosts (Atkinson 2011). Many of these Melittophile arthropods are found to be beetles (Ellis et al. 2008, Haddad et al. 2008, Marini et al. 2013, Audisio et al. 2014). One of the best known coleopteran beehive symbionts is Aethina tumida Murray (Coleoptera, Nitidulidae), which in their native sub-Saharan Africa are largely benign hive scavengers (Hepburn and Radloff 1998), but in North America (Hood 2004), Australia (Neumann et al. 2016) and many parts of the world (Neumann et al. 2016) are invasive pests, causing severe damage to apiaries. More recently, A. tumida has been found in Brazil (OIE 2016), raising awareness of beekeepers and researchers to previously unknown or unrecognized hive symbionts.

In this note, we describe a close association between a histerid beetle species and beehives. The predator Omalodes (Omalodes) foveola Erichson, 1834 has never been mentioned as a beehive symbiont, though its wide geographical distribution suggests that it may be a Melittophile species also in other regions. These findings suggest that the interactions between O. foveola and honey bees, and stingless native social bees (Meliponinae), need to be evaluated in order to determine whether there is a negative impact.

Beetles were reported inside Apis mellifera L. colonies in a commercial apiary located inside an orange farm in the state of São Paulo (Piracicaba city: 22° 42′ 53.0″ O; 47° 36′ 51.0″ S), Brazil. The apiarists first reported their observations to governmental animal health agencies as a case of A. tumida Murray (Coleoptera, Nitidulidae) infestation. On the basis of this report, we collected adult specimens of the beetle directly from the hives. Specimens were immediately labeled and stored in ethanol (70°GL). Some of the specimens were pinned in dry mount and the vouchers were stored in the Coleção Entomológica Pe. Jesus Santiago Moure - DZUP (Curitiba, Paraná, Brazil) and in the Coleção Entomológica Embrapa Florestas (Colombo, Paraná, Brazil).

The purpose was to investigate the Aethina notification: the floor and honeycombs of hives were visually inspected and the area immediately outside was inspected in search of adults and pupae.

Histerid beetle samples were first identified based on Almeida and Mise (2009), and Almeida et al. (2015). Later, specimens were sent to the Unidade Laboratorial de Referência Fitossantitária, Instituto Biológico, Secretaria da Agricultura e Abastecimento de São Paulo and also to the Laboratório de Sistemática e Bioecologia de Coleoptera (LSBC, Dr. Lúcia M. Almeida) and the Laboratório de Pesquisas em Coleoptera (LaPCoL, Fernando W. T. Leivas), both from Universidade Federal do Paraná—the latter with a long tradition of histerid systematics.

Adult beetles were found in the entrance and on the floor of the beehive model Langstroth, in variable numbers. After the initial detection, we inspected 21 hives (in the same locality) with beetles found in three more (inside the hive). An average of 12 beetles per beehive/colony was found. The species was later confirmed as the histerid beetle O. foveola Erichson, 1834.

The recent detection of A. tumida in the region had increased the awareness of the beekeeping community to any beetles found in beehives. However, misidentification of symbionts is probably common among beekeepers, leading to the risk that apiaries could be unnecessarily discarded (the invasive species and the native symbiont are illustrated in Figure 1).

Figure 1.
figure 1

Morphological comparison between Aethina tumida (a, c) and Omalodes faveola (b, d): dorsal view (a, b) and ventral view (c, d).

Full size image

In fact, there are sufficient morphological differences between the two species to allow prompt differentiation. O. foveola adults differ from A. tumida in the following characteristics: (i) a rounded, compact, and non-pubescent body; (ii) geniculate antenna, clubs with three compact antennomeres; (iii) a broad prosternal keel; (iv) hind coxae widely separated by a broad, truncate intercoxal process of the first ventrite; (v) undilated basal tarsomeres that are hairless beneath, and (vi) a short truncate elytra exposing two non-flexing terga (Figure 1b). In contrast, A. tumida adults differ from O. foveola by the following: (i) a pubescent and more elongated body; (ii) strongly transverse antennal clubs with the segments clearly separated; (iii) a narrow prosternal keel; (iv) hind coxae not widely separated by a broad, truncate intercoxal process; (v) basal tarsomeres dilated and hairy beneath, and (vi) a short elytra exposing a single tergite (Figure 1a) (sometimes the females may show more if they are close to egg laying). With respect to the larvae, Omalodes spp. usually have setae on the body and a long and falcate mandible, while the larvae of A. tumida have spines on the body and less evident mandibles (Teixeira et al. 2016).

Moreover, adults of O. (Omalodes) foveola differ from all known Omalodes (Omalodes) species in having frons with strong longitudinal sulcus medially; frontal stria slightly projected towards the epistoma medially lateral punctures of pronotum and indicated on entire lateral margin; and propygidium with a medial area smooth or with sparse punctures, with a pair of strong foveae on the posterior half (Moura 2014).

O. foveola is widely distributed in South and Central America (Mazur 2011) and was recorded for the first time in Paraná state (Brazil) by Leivas et al. (2013). This species is considered potentially useful to control Cosmopolites sordidus Germar, 1924, one of the main pests of banana cultivation (Mesquita 2003).

The association of Histeridae species with social insect colonies was already known (Caterino and Vogler 2002), although O. foveola was not noted as a Melittophile. In Manaus (Brazilian state of Amazonas), Hololepta (Leionota) reichii Marseul and other species of histerid have been recorded in stingless beehives (Hymenoptera: Apidae). Here, they act as natural enemies with intense predatory activity on stingless bee larvae and pupa (Coletto-Silva and Freire 2006). However, our account is the first record of O. foveola in A. mellifera colonies and only the second record of histerid beetles associated with Apidae nests to Brazil.

Finally, it is important to stress the need for further research on O. foveola ecology and interactions with bee colonies (especially in association with orange orchards). The wide distribution of this beetle species means that it could also be widespread as a beehive symbiont. The impact of the O. foveola on apiaries and also on native bees (Meliponinae) should also be further evaluated.