1988] Carpenter & Wenzel — Mischocyttarus from Costa Rica 93 
Nest diagnosis: Since the nest of pelor is a museum specimen not 
accompanied by notes, its original substrate and orientation are 
unknown. It may have been on the underside of a leaf, as suggested 
by an impressed central furrow along the line of pedicels. In the 
following description we assume that the substrate was horizontal 
and that the nest hung beneath it. This nest differs from those of all 
other known Mischocyttarus by its presumed mode of expansion 
(Fig. 7). A line of short pedicels supports cells which grow laterally 
parallel to the substrate. Successive rows of cells apparently point to 
alternate sides of the central line of pedicels. A central plate, proba- 
bly homologous to the back side of an ordinary Mischocyttarus 
nest, serves as the common base of back-to-back rows. Near either 
end of the rows, cells may grow at angles intermediate between the 
alternate rows and some cells are initiated on the walls of others, 
giving the nest the false appearance of a hemisphere of radially 
expanding cells (Fig. 8). 
Nest description: Egg shaped with long axis parallel to substrate, 
slightly flattened vertically, 34 mm long, 24 mm wide, 1 1 mm deep 
from substrate to lowest margin of downward pointing cells. Carton 
mottled brown with some pale stripes, brittle, composed of coarse, 
inflexible wood fiber and chips, reinforced with glossy secretion in 
region of pedicels and adjoining sheet. Three pedicels less than 2 mm 
long, aligned on central axis, initially supporting separated cells; 
fourth colinear pedicel secondarily added between wall of growing 
cell and substrate (Fig. 8c). Sheet (27 mm by 24 mm, but fragmented 
in specimen) fibrous and irregular, covering substrate, impressed 
along central line of pedicels with shallow furrow suggestive of the 
rib of a leaf; probably built outward from pedicels, peripherally 
fusing to side walls of those cells that contact substrate. Eight closed 
pupal cocoons (one broken), strongly domed about 2 mm beyond 
end of cells 10 mm long and covered over with wood fiber applied to 
silk, nine open cocoons. Eighty-four irregular cells, initial three lat- 
erally pointing to same side of the line of pedicels (primary side), 
younger cells radiating outward in all directions, more irregular on 
primary than secondary side, most parallel to substrate, may have 
walls straight or curved through 45 degrees, up to 6 mm deeper than 
their adjacent neighbors, may support younger cells of different 
orientation on their walls when divergent from or deeper than 
neighbors, one row of five short (less than 2 mm) cells pointing 
