Pseudoheriades, GRANDICEPS PETERS

Rozen, Jerome G. & Praz, Christophe J., 2016, Mature Larvae and Nesting Biologies of Bees Currently Assigned to the Osmiini (Apoidea: Megachilidae), American Museum Novitates 2016 (3864), pp. 1-48 : 41-42

PSEUDOHERIADES GRANDICEPS PETERS

Notes on Pseudoheriades grandiceps are based on nest fragments and cocoons pinned with adults from the United Arab Emirates. E.A. Sugden collected this material from trapnest blocks in which holes presumably 4 mm in diameter had been drilled. J.G.R.’s original interpretation was that females first lined the burrows with small leaves (or large leaf pieces) (fig. 64) or less commonly with petals (fig. 65) after which she provisioned the cell, oviposited in it, and then constructed a cell partition presumably made with resin since it was partly transparent, with a reflective (glassy) surface. However, see Remarks, below, for another possible explanation provided by C.J.P. The next cell was provisioned in front of the first, i.e., in linear series. Because cell partitions were constructed after the tunnel had been lined with leaves (or petals), they were attached to the leaf lining and not to the burrow wall.

An interesting feature that still needs confirmation was that the front end of the cocoon was apparently deposited before defecation started. This was revealed only with a close-up SEM micrograph of the glassy cell partition against which fecal pellets had been deposited (fig. 68). In normal light the transparent sheet of silk was invisible (fig. 66) but its texture with short silk threads was revealed on another specimen with the SEM (figs. 68, 69).

At the beginning of defecation, the first fecal pellets deposited were dark, approximately 0.625 mm long and 0.25 mm in maximum diameter, and rounded to tapering on the ends (fig. 68). Their shapes were discrete; when deposited, they did not fuse with one another (as they do in Ochreriades fasciatus, Rozen et al., 2015 , fig. 15). A few pellets, possibly among the last to be deposited, were extremely pale (fig. 67), possibly a discharge from the Malpighian tubules, as has been noted with other megachilids (e.g., Trachusa, Rozen and Hall, 2012 ). At the posterior end of cocoons flattened fecal streaks composed of opaque yellowish material as well as a few dark fecal pellets were often detected.

At the front end of the cocoon but behind the transparent silk outer layer, the seemingly loose fecal pellets were actually tethered one to another by silk strands, which presumably represents part or the outer cocoon layer (figs. 68, 69). Immediately behind the feces was the broadly curved front of the inner cocoon layer. The dense, opaque, white air portal (figs. 67, 70–72), centrally located on the front of the inner layer, could be identified because it contrasted with thin semitransparent fabric of the rest of the cocoon. Likely, air exchange between the interior of the cocoon and the outside occurs through the portal and from there, air diffuses in and round the feces and around the leaves to the exterior. No immature stages were preserved, and, consequently, none is available for description.

MATERIAL STUDIED: Two cocoons: United Arab Emirates: Nakhali, 40 km inland from Dubai. Reared blocks (E.A. Sugden) 54095F, 54127F; 1 cocoon: Dubai (Zabeel). Reared blocks (E.A. Sugden) 53888 D. From collection in USDA laboratory, Logan, Utah .

REMARKS: When J.G.R first examined the three cocoons, two of which had been pinned with the adults and cells from their nests, he was impressed by the fact that nest partitions were attached to the leaf-/petal-lined burrow wall. He interpreted this to mean that the nest-making female had first lined the burrow wall with the plant material and subsequently started making and provisioning the series of cells, one after another. C.J.P. suggested another explanation: might the female have appropriated the vacated nest of a Megachile , the cell of which had been lined with leaves and petal snippets since no other megachilid is known to use both petal-leaflining and resin in nest construction? Although none of the preserved nest materials gave a hint of the cocoons or feces of an original owner of the cells, the preserved nest material is limited. It is hoped the discovery of the next nest of P. grandiceps will provide a definitive interpretation. Terry Griswold kindly pointed to us an account on the nest of Pseudoheriades moricei by Krombein (1969). P. moricei also uses trap nests and uses resin for the construction of both partitions and plug, the latter also including pebbles. No hint of the use of petals or leaves is given by Krombein, suggesting that the leaves and petals observed in nests of P.grandiceps may have been previously placed by leafcutter bees.