Zethus (Zethoides) notatus Fox, 1899

Lopes, Rogério Botion & Melo, Gabriel A. R., 2025, New nests of Zethus reveal unexpected architecture variation in the olmecus species group (Hymenoptera, Vespidae), Revista Brasileira de Entomologia (e 20240126) 69, pp. 1-9 : 2

Zethus (Zethoides) notatus Fox, 1899

Nest 1

Collecting data: Translated from field notes of the second author: “RN37 – Zethus , nest constructed around filamentous fungus (same set of fibers that RN36 [belonging to a species of Trypoxylon] was hanging). No adult present. Four cells, three open and one closed. Marié River, 03.vii.1999. In 15.vii.1999, there was a dead adult in the plastic bag. Nest was probably being provisioned at the time of collecting, because there is a live larva in one of the cells. I was able to extract the larva and it is relatively small. Species most likely of progressive provisioning. The larva was placed in fixative with the adult”.

Overall aspect ( Fig. 1C ): the nest is composed of four exposed cells that close a circle, following a counter-clockwise direction (when observed from above), around the fungus. A very long “ornament” (a lower prolongation) made of vegetable matter extends downwards following the fungus filament.

Fixation: the nest is firstly attached through long strips of cut foliage and resinous matter that wrap around three filaments of a Marasmius fungus in a downward spiral ( Fig. 1D ) that is then fixed in the basolateral side of what probably is the first cell. The following cells are fixed adjacently on the underside of the previous cell.

Brood cells: The set of four cells were disposed in a circular pattern. Each cell spirals upward, with the fungus filament as a central axis. Each cell makes an approximate 160° turn, leaving the opening facing almost in the opposite direction of the bottom, giving a J-shape to the cell. The cells are more robust at the bottom, narrowing along the curvature and becoming cylindrical on the apical straight half. The cells are built in a manner that the bottom of each cell begins at approximately the same height in lateral view. The heights of the openings are also at the same level. Each cell is built adjacently on the underside of the previous one, where there is contact until about half of the cell length. Although very close, the fourth cell closes the circle but does not touch the first cell. The cells are made of long strips of cut leaves, tightly glued together, that spiral towards the opening ( Fig. 1E ). While it is possible to discern each layer, it is difficult to stablish the end and beginning of each strip. The space between each strip is coated with a blackish resinous matter, leaving the light-brown apical margin of the strip free.

Ornament ( Fig. 1F ): projecting from the underside of each cell, a series of long leaf strips converge centrally towards the fungus filament, with six strips originating from under the first cell, seven from the second, two from the third and two from the fourth. These cuttings, once converged, lie parallel to the axis of the fungus filament, fixed to it. The spaces between leaf strips are also coated in dark resinous material, with the light uncoated margin outwards oriented. Other cuttings are placed along the ornament but only four form at the apical end. One fragment was broken off.

Measurements: Length of fungus filament above nest = 85, 75 mm. Nest:height = 12.16 mm; width = 19.75 mm.Ornament = 29.39 mm.Cells: length = 8.43 mm ± 0.38mm; distance between bottom of adjacent cells = 4.27 mm ± 0.35 mm; distance between bottom of cell and opening of previous cell= 11.24mm ± 0.50 mm; opening diameter= 3.80 mm ± 0.10 mm.

Figures

Figure 1 Nest of Zethus notatus. A) Nest in collecting site. B) Lateral view of nest. C) Overhead view of nest. D) Area of fixation of the nest, revealing the leaf threads wrapping around the fungus. E) Closeup on the arrangement of strips used to build cells.F) Detailed view of the ornament.