OBSERVATIONS OF XENORHYNCHIUM NITIDULUM 
(FABRICIUS) (HYMENOPTERA, EUMENINAE), 
A PRIMITIVELY SOCIAL WASP 
By Mary Jane West-Eberhard* 
Smithsonian Tropical Research Institute 
Introduction 
Until recently primitively social wasps, with more than one female 
sharing a nest but without a reproductive division of labor, were 
considered rare. For many years, the only such wasps known were 
the five species cited by Wheeler (1928) in his classic book on the 
social insects. More primitively social wasps are now known (for a 
partial list see West-Eberhard, 1979). It is clear, however, that many 
more remain to be discovered, and information on the biology of 
primitively social species is still scarce. It therefore seems worth- 
while to report the following brief notes on Xenorynchium nitidu- 
lum (Fabricius), a primitively social wasp found in India. The 
observations reported here were made on nests collected in the vil- 
lage of Janla, Puri District, Orissa (about 20 degrees N. Latitude) in 
November, 1979. X. nitidulum is widely distributed in India. Vecht 
(1963 p. 112) cites Dover and Rao (1922) as recording this species 
from Calcutta, Pusa, Bangalore, Lucknow, Kashmir, and Lahore 
(Punjab). 
Nest Structure and Contents 
Xenorhynchium nitidulum builds a nest consisting of several 
barrel-shaped mud cells coated with an amber-colored substance 
that is sticky when fresh, and that later forms a hard lumpy coating. 
This Coating strengthens the rather fragile mud walls of the cells 
which are only 0.25-0.5 mm thick. It may also afford some protec- 
tion against insect predators and parasitoids, as further discussed 
below. Horne (1870) and Dutt (1912) report that the gummy sub- 
stance comes from the trees Ficus religiosa and Acacia catechu. 
* Address for correspondence: Escuela de Biologia, Universidad de Costa Rica, 
Ciudad Universitaria, Costa Rica, Central America. 
Manuscript received by the editor September 25, 1987. 
317 
