184 
Psyche 
[Vol. 89 
1937, Beaumont 1958). These traits are presumed to function in 
preventing sting penetration by host defenders and in facilitating 
stinging or injuring the hosts. 
Investigators have noted these unique traits primarily among the 
European vespine inquilines and their hosts (Beaumont 1958, 
Bischoff 1931, Carpenter and Pack-Beresford 1903, Eck 1979, Rob- 
son 1898, and Weyrauch 1937). One of these inquilines, Vespula 
austriaca (Panzer), has only recently been found in colonies of a 
Nearctic species [ V. acadica (Sladen) Reed et al. 1979] and behav- 
ioral interactions with members of the host colony have been docu- 
mented (Reed 1982). Although researchers have discussed the 
external morphology of V. austriaca in relation to the European 
host, V. rufa (L.), no comparisons have been made between the 
Nearctic host and V. austriaca. Consequently, the objectives of this 
paper are: (1) a morphometric comparison between the V. acadica 
queen and the parasite; (2) descriptions of certain external features 
such as the stings, mandibles, femora, and abdominal sclerites; and 
(3) a survey of exocrine glands of the two species. 
Materials and Methods 
Seven external body parts were measured in pinned specimens of 
the host queen and parasite using a dissecting microscope equipped 
with an ocular micrometer. These characters have been commonly 
used in other biometrical studies of vespid wasps (Blackith 1958, 
Eck 1979, Eickwort 1969). Specimens were obtained from local col- 
lecting sites (Reed 1982) and from several North American entomo- 
logical museums (Acknowledgements). Measurements of the inter- 
ocular distance, mesonotal length, hind tibial length, and forewing 
length followed the description and diagrams of Eck (1979). Also, 
the length of the front femur was measured from the base to the 
apex in the same manner as the hind tibial length, while the width 
was taken at its widest point. Head width was measured in dorsal 
aspect, behind the eyes along the vertex, and between the upper 
edges of the genae. The mesonotal length was measured along the 
midline from the anterior prescutal suture to the posterior trans- 
scutal suture. The length and midline width of the first gastral ter- 
gum were also determined in dorsal view. 
Scanning electron micrographs (SEM) of the sting apparatus of the 
host and three parasite species were prepared. Dissected stings were 
