Calliopsis zebrata

Rozen, Jerome G., 2008, The Solitary Bee Calliopsis zebrata: Biological and Distributional Notes and Description of Its Larva (Hymenoptera: Andrenidae: Panurginae), American Museum Novitates 3632 (1), pp. 1-12 : 6-11

DESCRIPTION OF MATURE LARVA OF CALLIOPSIS ZEBRATA

Figures 8–21

The following larval description of Calliopsis zebrata is based on both the predefecating and postdefecating forms. It is quite similar to the description of the yellowbanded Calliopsis (i.e., Nomadopsis , s.l.) presented by Rozen (1958). The terminology has been updated to reflect current anatomical usage, and the presentation has been formatted somewhat differently. Except for details of integumental sculpturing now possible through SEM examination, the description seems to be applicable to all species the larvae of which are known. Thus, it will probably be of little value in distinguishing between species or even subgenera, since larval differences between them apart from size are subtle at best. Perhaps when the surface sculpturing of other species is studied by SEM, diagnostic features will be discovered. No differences were found whereby postdefecating larvae of the two subspecies could be differentiated.

Specimens examined for viewing with the Hitachi S-5700 scanning electron microscope (SEM) were critical-point dried and coated with gold/palladium. Others were studied with a Zeiss EVO 60 SEM. Still others, after heads were severed from bodies, were cleared in an aqueous solution of sodium hydroxide, washed, transferred to ethanol, stained with Chlorazol Black E until lightly colored, and examined in glycerin with stereomicroscope and compound microscope to identify internal head ridges and tentoria.

A major problem when examining the postdefecating larva with an SEM was the extensive coating of the dried, transparent secretion that covered them. The coating material, of uncertain origin, is secreted by larvae of many bee taxa when they enter diapause and presumably protects the individual from desiccation. This material obscures fine surface features when they are coated with gold/palladium. Specimens, when first cleared in an aqueous solution of sodium hydroxide, seem to lose some of this coating, but, as can be seen in figure 13, the labiomaxillary region remains coated even after the head has been completely cleared in the boiling aqueous solution. This coating is not seen on the prothorax of the same specimen (figs. 11, 12), perhaps suggesting that it did not reach that part of the anatomy or that it was much more thinly applied there than in the labiomaxillary area, alluding to the possibility that its origin might be the salivary gland.

The single predefecating larva collected was first cleared, stained, and then examined with both compound and stereomicroscopes. Its head was then critical-point dried, coated, and studied with the Hitachi SEM. As anticipated, it had not yet been coated with the diapausing secretion (compare figs. 13 and 20). I questioned whether the intensive preparation of this specimen might have adversely affected its integument, but a comparison with the less harshly treated postdefecating larval head (fig. 1) differs little from the predefecating head (fig. 19) and suggests little difference between the two. Thus, close-up SEM micrographs of the mouthparts (figs. 20, 21) would seem to show the true verrucosity of the labiomaxillary region.

The following description refers to all known mature larvae of Calliopsis zebrata .

HEAD: Integument with scattered sensilla that are not setiform; dorsal surfaces of maxilla and hypopharynx densely spiculate (fig. 21); lateral surfaces of epipharynx spiculate; integument particularly of maxillary apices, labial apex, and hypopharynx but also most of head capsule wrinkled and with hypopharynx and apex of labiomaxillary region deeply verrucose (figs. 10, 13, 19–21). Integument unpigmented except for mandibular apices.

Head (figs. 10, 13, 18–21) moderate in size compared with body size; head capsule distinctly wider than length measured from top of vertex to lower clypeal margin in frontal view. Tentorium complete, including dorsal arms, but thin. Anterior tentorial pit well removed from anterior mandibular articulation (figs. 10, 19); posterior tentorial pits in normal position; postoccipital ridge uniformly moderately developed; median longitudinal thickening of head capsule (coronal ridge) absent; hypostomal ridge moderately developed, its posterior section curving inward abruptly to meet tentorial bridge while dorsal ramus continues posteriorly and fades; pleurostomal ridge moderately developed; epistomal ridge laterad of (below) anterior tentorial pit moderate in length; ridge between pits absent. Parietal bands evident as integumental scars (figs. 10, 19). Antennal prominence rather weak (fig. 19); antennal disc as seen on cleared specimen moderately small, its diameter about one-half distance from its lowest rim to center of anterior tentorial pit (distances measured in maximum profile); antennal papilla projecting weakly, its height less than one-half basal diameter, each bearing 3 to 4 sensilla (fig. 14). Vertex evenly rounded, moderately broad, as seen from side (fig. 18), without projections. Labrum projecting anteriorly as far as clypeus in lateral view (fig. 18), moderately long in frontal view, apically rounded, spiculate laterally, and with pair of acutely pointed, sensilla-bearing tubercles (figs. 10, 18, 19); epipharynx with median cluster of sensilla near front edge.

Mandible (approximately as in Rozen, 1958: figs. 34, 35) in outer or inner views tapering evenly to narrowly pointed apex; dorsal apical edge with linear row of sharp teeth (fig. 21) that broadens out at cusp; ventral apical edge with teeth that are fewer and smaller than those of dorsal apical edge; cusp weakly produced in dorsal and ventral views; apical concavity shallow, facing hypopharyngeal surface; outer mandibular surface with small, seta-bearing tubercle toward base; dorsal surface finely spiculate. Labiomaxillary region weakly projecting in lateral view (fig. 18), so that its apex exceeded by apex of labrum in lateral view; apex of maxilla projecting as far as or slightly farther than apex of labium in lateral view (fig. 18). Cardo, stipes not evident as sclerites although cardostipital articulation suggested by external folding of integument; articulating arm of stipital sclerite not evident although hypopharyngeal groove pronounced; maxillary palpus (fig. 21) positioned at apex of maxilla, small, shorter than basal diameter, somewhat obscured by maxillary integumental verrucosities. Labium weakly divided into prementum and postmentum; premental sclerite not evident; labial palpus small, scarcely projecting. Salivary opening (figs. 10, 11, 19, 20) a Ushaped slit subtending hypopharyngeal groove, without lips; salivary duct attached to bottom of U; area bounded by U-shaped slit and hypopharyngeal groove apparently slightly produced. Hypopharynx protuberant, projecting forward, more or less as far as labial apex.

BODY (figs. 8–12, 15–17): Integument with fine, scattered, nonsetiform sensilla and with spiculate areas as follows: prothorax (figs. 10– 12, 19) with large rounded to sharply pointed spicules densely and uniformly arranged on dorsal and lateral surfaces; these spicules gradually becoming fine on lower sides of body and ventrally; other body segments with spicules fine, inconspicuous, often evenly spaced, but absent on lateral body surfaces. Body form (figs. 8, 9) moderately robust; intersegmental lines moderately weakly incised on predefecating form; on postdefecating form ventral intersegmental lines more pronounced; dorsal intrasegmental lines not evident; paired dorsal tubercles present and moderately large on all thoracic segments and on abdominal segments 1–6, but diminishing on abdominal segments 7, more so on 8, and scarcely noticeable on 9; all tubercles conical (contrasting with transverse tubercles of Halictinae) but with basal transverse diameters clearly greater than basal longitudinal diameters; apices of midbody segments (abdominal segments 3 and 4) of some postdefecating larvae tending to be slightly flattened (fig. 15), presumably an artifact of body weight, as has been observed with other taxa having paired dorsal tubercles ( Rozen and Özbek, 2008); integument of apices (fig. 15) wrinkled, weakly verrucose, contrasting with dorsal integument elsewhere; abdominal segment 9 not produced ventrally; abdominal segment 10 positioned medially on 9 as seen in lateral view (figs. 8, 9); anus apical on 10. Spiracles small, subequal in size, not on sclerites or tubercles; peritreme (figs. 16, 17) present, moderate in width, about as wide as diameter of atrial opening; atrium projecting beyond body wall, with rim, globose; atrial wall smooth (without denticles or ridges); primary tracheal opening with collar; atrium in lateral view (fig. 17) small relative to width of subatrium; subatrium long, consisting of about 20 chambers. Male with median, transverse integumental scar on venter of abdominal segment 9; female with two pair of small circular scars on venter of abdominal segments 8 and 9, with those on 9 closer than those on 8.

MATERIAL STUDIED: Seven postdefecating, 1 predefecating larvae, AZ: Coconino Co.: Flagstaff, VIII-30-2007 (J.G. Rozen); 3 postdefecating larvae, OK: Blaine Co.: Watonga: Roman Nose State Park, V-18-1977 (C.D. Michener).

REMARKS: The wrinkling and fine verrucosity of the head integument, particularly noticeable on the apices of the labiomaxillary area is apparently characteristic of most Calliopsis in that is found in exemplars of Nomadopsis s.s., Micronomadopsis , Calliopsis , Calliopsima , and probably others, as well as elsewhere in the Panurginae. This feature was unexpected and needs further study.

Figures

Figs. 8–9. Macrophotographs of preserved mature larvae, lateral view, of Calliopsis z. bobbae (left) and C. z. zebrata (right).

Figs. 10–15. SEM micrographs of postdefecating larva of Calliopsis z. bobbae, cleared by being boiled in aqueous solution of sodium hydroxide. 10. Head, frontal view, 11. Prothorax showing dense pattern of spiculation identified by rectangle in fig. 10. 12. Close-up of spicules identified by rectangle in fig. 12; note acute apical projections. 13. Left side of labiomaxillary region, frontal view, showing coating that failed to be removed after head cleared. 14. Antennal papilla, frontal view. 15. Apex of right dorsal tubercle of abdominal segment 4.

Figs. 16, 17. Larval spiracle of Calliopsis z. bobbae. 16. SEM micrograph of spiracular peritreme with elevated rim of postdefecating form, external view. 17. Macrophotograph of entire spiracle of predefecating form, lateral view.

Fig. 18. Diagram of head of mature larva of Calliopsis zebrata, lateral view; verrucosities of labiomaxillary region not depicted.

Figs. 19–21. SEM micrographs of Calliopsis z. bobbae. 19. Head of predefecating larva, frontal view. 20. Close-up of mouthparts of same, frontal view. 21. Close-up of right mandible, maxilla, and hypopharynx, frontolateral view, showing fine teeth along dorsal apical edge of mandible and spicules on dorsal surfaces of hypopharynx and maxilla.