Osmia chalybea

Rozen, Jerome G. & Hall, H. Glenn, 2011, Nesting and Developmental Biology of the Cleptoparasitic Bee Stelis ater (Anthidiini) and Its Host, Osmia chalybea (Osmiini) (Hymenoptera: Megachilidae), American Museum Novitates 2011 (3707), pp. 1-40 : 27-30

OSMIA CHALYBEA

EGG/MATURE OOCYTE

Figures 7 , 70, 71, 73–75

DESCRIPTION: Egg length 3.2–3.58 mm; maximum width 1.1–1.3 mm (N = 5); mature oocytes length 3.0 mm; maximum diameter 1.1 mm. Shape slightly curved with ventral surface weakly concave in lateral view; anterior end broadly to narrowly rounded in lateral view; posterior end also variably rounded; maximum breadth posterior to midbody (figs. 71, 72); micropyle a cluster of pores (figs. 74–76) surrounded by faint converging lines on normally curved surface of front of egg near anterior pole, not visible under stereomicroscope. Egg color translucent whitish; chorion under stereoscope clear, shiny, glassy. Under SEM examination chorion featureless except for micropylar area.

FIFTH INSTAR

Figures 79–81 , 91

The following is based on both defecating and postdefecating forms. DIAGNOSIS: The last larval instar of Osmia chalybea is remarkably similar to the recently described larva of O. (Ozbekosmia) avosetta Warncke ( Rozen et al., 2010b) . They can be distinguished in that the length of antennal papilla of O. avosetta is three times its basal diameter and the dorsal apical edge of the dorsal mandibular tooth is crenulate (ibid.: figs. 35, 36), whereas in O. chalybea the length of the antennal papilla is less than twice its basal diameter and the dorsal apical edge of the upper mandibular tooth is com- FIGURES 70–72. Diagrams of eggs of Osmia chapletely smooth (fig. 91). lybea (70, 71) and Stelis ater (72), lateral view, anterior end toward left, all to same scale; two diagrams DESCRIPTION: Head (figs. 81, 91): Setae of O. chalybea demonstrate variation in shape possilong and abundant; those of frons shorter bly a result of different ages of embryos. and those of labrum very short; those of maxillary and labial apices straight, forward projecting. Head pigmentation generally weak (further weakened by clearing with aqueous solution of sodium hydroxide); following areas pigmented: labrum including labral sclerite and area distad of it; hypostomal ridge; mandibular apex and points of articulation; internal head ridges at articulation with mandibles; following sclerites faintly pigmented: cardo; stipital rod and sclerotized apex and articulating arm of stipes; premental sclerite; antennal papilla and all palpi. Fine spiculation restricted to lateral surface of paired hypopharyngeal lobes. Area immediately above hypostomal ridge and just behind posterior mandibular articulation not produced as downward-directed tubercle as present in many Coelioxys ( Rozen and Kamel, 2007: fig. 47). Coronal ridge short, nearly absent; postoccipital ridge well developed; when viewed from above, ridge bending forward from each side, so juncture at midline obtusely angled; hypostomal ridge well developed, giving rise to pronounced dorsal ramus that extends posteriad from middle of ridge nearly to postoccipital ridge where it abruptly stops; anterior tentorial pit approximately equally distant from anterior mandibular articulation and basal ring of antenna; epistomal ridge present only laterad of anterior tentorial pits; tento-

rium robust including dorsal arms. Parietal bands faintly evident. Antennal papilla small, length somewhat less than twice basal diameter, bearing two to three sensilla. Lower margin of clypeus strongly angled upward at midline, so that at midpoint margin approximately at level of anterior tentorial pits. Labral sclerite transverse, faintly to moderately pigmented; labrum lacking darkly pigmented median spot extending from labral sclerite to apical labral margin as in fully pigmented Coelioxys larvae ( Rozen and Kamel, 2007: figs. 44, 45); apical labral margin moderately broadly emarginated in postdefecating form to deeply emarginated in some defecating larvae

(probably an indication of soft, pliable texture of labral apex).

Mandible (fig. 90) moderately robust; apex bidentate with ventral tooth longer than dorsal tooth; both teeth acutely pointed; dorsal apical edge of dorsal tooth smooth; ventral apical edge of upper tooth and both edges of ventral tooth unmodified; apical concavity pronounced, sharply defined basally; cuspal area not produced; outer surface with single basal seta. Cardo present as sclerite; stipital rod slender; articulating arm of stipes evident; maxillary palpus moderately slender, longer than antennal chalybea . 78. Macroptic photograph of entire larva, lateral view. 79. Microphotograph of spiracle showing spined atrial wall, peritreme,

and nearly parallel-sided subatrium. 80. SEM micrograph of salivary lips showing parallel ridges of inner surface of lower lip, frontal view.

papilla. Labium clearly divided into prementum and postmentum; apex normally wide; premental sclerite weakly sclerotized; postmentum nonsclerotized. Salivary lips projecting, transverse, width about equal to distance between bases of labial palpi. Hypopharynx consisting of two widely separated lateral lobes, lateral surfaces of which are spiculate.

Body (figs. 78): Body setae moderate in length, not rising from swollen bases as in Osmia avosetta , extremely abundant, even more so than in O. avosetta ; pleural area of abdominal segment 8 with approximately 80 setae; integument with fine network of irregular polygons, without spicules. Body form robust; on defecating form intersegmental lines at most weakly incised and intrasegmental lines not evident; on postdefecting form intersegmental lines well incised on anterior part body, less so on posterior part and intrasegmental line well formed on anterior part but becoming less so posteriorly, not evident beyond abdominal segment 6; paired body tubercles absent; middorsal body tubercles evident on midbody segments of postdefecating larva; pleural swellings moderately developed; abdominal segment 10 short, attached to approximate middle of segment 9; anus positioned toward top of segment 10. Spiracles (fig. 79) well sclerotized, unpigmented, subequal in diameter; atrium globular with width somewhat greater than depth, projecting above body wall, apparently without rim; peritreme narrow, so diameter of atrial opening approximately four times peritreme width; atrial inner surface with fine, sharply pointed, concentrically directed spines; primary tracheal opening with collar; subatrium perhaps variable in length, with as many as 12 chambers; externally, subatrium approximately parallel sided with first and innermost chamber of equal width. Male and female sex characters unknown.

MATERIAL EXAMINED: Numerous postdefecating and defecating fifth instars preserved various times in April, May, and June, 2010.

Figures

FIGURES 1–7. Trap nests used in the study of Osmia chalybea and Stelis ater. 1. Two trap nests deployed in the field. 2. Front end of U-shaped trap nest. 3. Front end of circular trap nest, showing circular openings to boreholes lined with paper straws and unlined; note that two exhibit nest closures. 4. U-shaped trap nest seen

FIGURES 78–80. Last larval instar of Osmia

FIGURES 81–86. Macroptic photographs of last larval instar of Stelis ater. 81. Entire postdefecating form, lateral view. 82–84. Head of same, front, lateral, and ventral views, respectively; atp = anterior tentorial pit. 85. Entire early fifth instar, lateral view. 86. Posterior part of abdomen of another specimen, lateral view, showing segmentation of abdominal apex.