An Anomalous Specimen of Perdita wasbaueri Timberlake with only One Antenna (Hymenoptera: Andrenidae)

Research into aberrant bees has largely focused on sex anomalies (Wcislo et al., 2004; Engel, 2007; Hinojosa-Dı́az et al., 2012), eye and ocellar deformities (Gibbs, 2010; Engel et al., 2014), and the effects of stylopization (Salt, 1927); little attention has been paid to other types of anomalies. With the exception of stylopized individuals, anomalous bees have been rarely reported in the family Andrenidae. Whether this is due to a lower incidence of anomalous bees, or a relative lack of research on the family, is unknown. Here, we report on an andrenid bee in the genus Perdita Smith with only one antenna. The specimen — a female Perdita (Heteroperdita) wasbaueri Timberlake, 1960 — is completely missing the left antenna (Fig. 1). There is no sign of an antennal socket; instead, smooth, unbroken integument covers the area where the antennal socket should be. The head of the bee is slightly malformed, with the left side of the face slightly compressed and the left compound eye rotated slightly back along the gena. The left side of the face also appears to lack the normal amount of pubescence, though some of this may be due to matting as a result of collection method. The anomalous specimen is slightly larger than average with a body length of 2.8 mm; wild type females of P. wasbaueri have an average body length of 2.6 mm and typically range in size from 2.4–2.9 mm (n = 10). Compared to two wild type specimens with the same body length, the anomalous specimen has a normal head width of 0.88 mm, but the head height of 0.67 mm (measured through the midline of the face) is slightly reduced compared to 0.73 mm for both wild type specimens. The anomalous specimen also has only female characters, no other anomalous characters are apparent on the rest of the bee, and there is no evidence of stylopization, which is known to create deformities in bees (Salt, 1927). The anomalous bee was discovered in the unsorted Perdita of the Essig Museum of Entomology at UC California, Berkeley (ascension number EMEC 741200).This specimen was collected by A. E. Michelbacher, 15 miles west of Blythe, California, on the 22nd of June, 1964. The bee was caught on flowers of Asclepias sp. (Asclepiadaceae), indicating that this bee was both capable of flight and locating floral resources despite its deformity. Whether the bee was actively nesting is unclear; the scopa and body of the bee are devoid of pollen and pollinia. This specimen joins two previously reported cases of antennal anomalies in bees: a male Augochlora pura (Say) with shortened and malformed flagellomeres (Sivik, 1962) and a female Nomada vicina Cresson lacking the right antenna (Rodeck, 1943). The specimen of N. vicina differs from the current specimen in two ways: it has a shallow invagination near where the antennal socket should be, and it is missing the right antenna, while the current specimen of P. wasbaueri is missing the left antenna.