Agapostemon (Agapostemon) sericeus (Forster)

Portman, Zachary M., Arduser, Mike, Lane, Ian G. & Cariveau, Daniel P., 2022, A review of the Augochloropsis (Hymenoptera, Halictidae) and keys to the shiny green Halictinae of the midwestern United States, ZooKeys 1130, pp. 103-152 : 103

Agapostemon (Agapostemon) sericeus (Forster)

Diagnosis.

The female of Agapostemon sericeus can be recognized by the combination of the metallic green metasoma (as in Fig. 4C ) and the reticulate sculpturing of the scutum (Figs 5B , 6A ). It is most similar to Agapostemon splendens , but Agapostemon splendens has the scutum more punctured (Fig. 6B ) rather than reticulate, and Agapostemon sericeus can be further distinguished by its sharply angled dorsolateral ridge of the pronotum (Fig. 5B ) and by having the ventral pleural tubercle flush with the plate (Fig. 6C ).

Male Agapostemon sericeus have S3 and S4 with a low transverse swelling and generally have distinct yellow marks on the apical sterna (Fig. 7C ). They are most similar to males of Agapostemon texanus but can be distinguished by the relative lengths of F1 and F2: in Agapostemon sericeus F1 is slightly more than half the length of F2, whereas in Agapostemon texanus F1 is about three-fourths the length of F2 (Fig. 10 ). They can also be separated by the genitalia (see Roberts 1972).

Remarks.

Agapostemon sericeus was previously known as Agapostemon radiatus (Say) (e.g., Mitchell 1960; Roberts 1972) but was synonymized by Day and Fitton (1977).

Females of Agapostemon femoratus Crawford, primarily a western species not recorded east of New Mexico, Colorado and Wyoming by Roberts (1972), are essentially identical to females of Agapostemon sericeus , though the males are quite distinct, possessing a grossly enlarged hind femur, its width and length equal or nearly so. The key in Roberts (1972) indicates the scutum of female Agapostemon sericeus is more distinctly punctate than Agapostemon femoratus , but we do not consider this a reliable separating character. Curiously, there are several Missouri records of Agapostemon femoratus from the 1960s identified by Roberts in separate online databases, (discoverlife.org, Ascher and Pickering 2022), but these were not included in his 1972 revision. We have not seen these specimens, but assume they represent mis-determined females of Agapostemon sericeus , not Agapostemon femoratus .

Figures

Figure 4. Agapostemon female metasomas A entirely black (Agapostemon virescens pictured) B dark brown with amber (Agapostemon melliventris pictured), note this is a darker specimen C metallic green (Agapostemon texanus pictured).

Figure 5. Agapostemon female pronotal collar and scutum A Agapostemon texanus doubly punctate B Agapostemon sericeus rugosopunctate with sharp pronotal angle outlined in red C Agapostemon splendens densely punctate with obtuse pronotal angle outlined in red.

Figure 6. Agapostemon thorax characters (anterior of bee to left, " mc " refers to the base of the middle coxa) A Agapostemon sericeus close-up of rugosopunctate scutum B Agapostemon splendens close-up of densely punctate scutum C Agapostemon sericeus with ventral pleural tubercle flush with rest of plate D Agapostemon splendens with ventral pleural tubercle slightly upraised. Yellow arrows indicate the ventral pleural tubercle.

Figure 7. A Agapostemon virescens metasomal sterna with unmodified S 3 and S 4 B Agapostemon texanus metasomal sterna with swelling on S 4 (and S 3 to a lesser extent) C Agapostemon sericeus modified S 3 and S 4 D Agapostemon texanus modified S 3 and S 4.

Figure 10. Male antennae with segments highlighted with bars to help illustrate their relative lengths A Agapostemon sericeus B Agapostemon texanus. Scale bars: 500 µm, both images at same scale.