Melecta species

ROZEN, JEROME G. & ÖZBEK, HIKMET, 2003, Oocytes, Eggs, and Ovarioles of Some Long-Tongued Bees (Hymenoptera: Apoidea), American Museum Novitates 3393, pp. 1-36 : 23-27

Melecta species

The egg (described below) of an unknown species of Melecta was found attached by its posterior end to the cell closure of Anthophora (Lophanthophora) nr. fulvitarsis Brullé (kindly identified by Robert W. Brooks, University of Kansas). The long axis of the cell was vertical, and the egg hung straight down from the smooth inner surface of the closure. Although the lower part of the cell had been destroyed during our excavation, the cell closure and the upper part remained. We immediately noticed two conspicuous holes on the inner surface of the closure, the closest to the egg being 3 mm away (figs. 60, 61). Each hole was about 1 mm in diameter and was filled with a rough mass of soil that extended beyond the inner surface of the closure. Later, another egg (or egg chorion) was seen imbedded in the dried provisions clinging to the sidewall; this had either hatched, been dropped onto the provisions when deposited, or been dislodged from the closure during our excavation. Thus two eggs, presumably from different females (otherwise, why two holes?), had been introduced into the closed cell.

Hence, the oviposition behavior of this species appears almost identical to that described for Melecta separata callura (Cockerell) by Thorp (1969) and for M. pacifica Cresson by Bohart (1970). Malyshev’s (1928: fig. 7) photograph of the egg of Melecta armata Panzer attached to the cell closure of Anthophora acervorum Linnaeus is consistent with these accounts. Torchio and Youssef (1968) reported similar observations for M. pacifica , Xeromelecta californica , and Zacosmia maculata , as did Torchio and Trostle (1986) for X. californica . Because of the small size of the hole in the cell cap reported for most of these species, it seems likely that these bees use the apex of their metasoma to punch through the closure. In the case of the unknown species of Melecta discussed here, the outer part of the closure did not reveal exterior evidence of the hole through which the eggs had been inserted, and no mention of this was made by Thorp, Torchio and Youssef, or Torchio and Trostle with respect to the melectines they studied. However, one of us (J.G.R.) made observations on X. californica attacking nests of Anthophora occidentalis Cresson (adults kindly identified of Robert W. Brooks, University of Kansas) at Cedar Point Biological Station, University of Nebraska, north of Ogallala, Keith Co., Nebraska, July 12–19, 1988. From J.G.R.’s unpublished preliminary manuscript, the following is excerpted: ‘‘Egg insertion holes were discovered on the inner surfaces of the cell closures of 15 cells.... In only two of the cells was the hole seen to penetrate to the outer surface, an indication that the female cuckoo [bee] usually patches the hole on the outer surface after oviposition.... In most (but not all) parasitized cells, a large depression 4–5 mm wide and 2–3 mm deep, sometimes accompanied by scratch marks, occurred on the outer surface, indicating that the Xeromelecta female first made a depression with her mandibles before drilling (or punching) a small hole less than 1.0 mm in diameter through [the cell closure] to the cell lumen, presumably with the tip of her metasoma.’’ Samples of these cell closures are in the collections of the American Museum of Natural History. Such variable behavior may depend on whether the cell closure material is still moist from construction so that it can be easily reinstalled by the female cleptoparasite after she oviposits. However, the observations do seem to suggest that the cleptoparasite can oviposit in nests where the cell closure has already dried after being constructed by the Anthophora female.

Unexplained for any melectine is how the ovipositing female manipulates the apex of her metasoma to attach the egg to the cell closure some distance (in the case of our observation, 3.0 mm) from the hole in the cell cap and by what means the posterior end of the egg adheres to the closure.

The following description is based on field notes made at the time of finding the egg attached to the cell closure. It was allowed to dry, still attached, so that pictures could be taken of it relative to the insertion hole (figs. 60, 61). Subsequently, the shriveled egg was removed and studied by SEM.

EGG (figs. 56–58, 60, 61): Length 3.0 mm; maximum diameter 0.64 mm; size relative to intertegular distance unknown because female not collected. Shape elongate, approximately symmetrical around its moderately curved long axis; anterior and posterior ends rounded; maximum diameter near anterior end, gradually tapering to other end; micropyle not evident under stereomicroscopic examination; under SEM (figs. 56–58), micropylar area easily identified (figs. 56, 57) but pores not certainly seen; area covered by sculpturing that seems to lead to one edge of the elliptical micropylar area. Chorion smooth, opaque, dull, and white, lacking sculpturing and other ornamentation as seen by stereomicroscope; under SEM (figs. 56– 58), anterior end with strong polygonal pat­ tern created by grooves in chorion, the polygons becoming more elongate toward anterior pole; this pattern bilaterally symmetrical, not radially symmetrical (fig. 56).

MATERIAL STUDIED: One egg, Turkey: Erzurum: 22 km WSW Oltu, VI­25–2001 (J.G. Rozen) .

REMARKS: The difference from the oocyte of Melecta albifrons albovaria , described above, and the egg of Melecta sp. is slight and pertains only to the subtle interpretation of the position of the widest diameter; this egg may well be that of M. albifrons albovaria , the most common of the three species of Melecta found at the site.