274 
G.R. Brown 
rounded lobes; genitalia as in Figure 6, parameres 
short, broad and apically rounded. 
Female 
Measurements 
10-19 mm. 
Colour 
Dark brown to black. Setae white. 
Structural features 
Head subrectangular, wider than long (1.16:1), 
narrowed ventrally, dorsal angles broadly 
rounded; clypeus truncate, not carinate, closely 
punctate; frons sparsely punctate becoming 
coarsely and closely punctate ventromedially; 
vertex sparsely punctate; pronotum 
subrectangular, wider than long (1.73:1), slightly 
narrowed posteriorly, reticulate, very finely and 
closely punctate, anterior margin with line of 
coarse punctures; mesoscutellum punctate; 
propodeum truncate with short dorsal surface, 
finely and closely punctate, lateral surface 
impunctate and polished with few punctures 
dorsally and posteriorly; tergites finely and closely 
punctate overlain with coarser punctures, 
becoming sparsely punctate anteriorly on posterior 
tergites; T1 truncate with preapical Carina defined 
by finely and rugosely punctate band; T2 with 7 
(including preapical) evenly spaced complete 
transverse carinae, smooth anterior to basal carina 
and between apical and preapical carinae; T3-4 
with preapical carina and associated 
microsculpture as T1 but less well defined; T5 
rugosely punctate posterolaterally; sternites 
punctate becoming closely punctate laterally 
especially on S3-4; S5 (Figure 10) rugose basally 
becoming obliquely carinate posteriorly; pygidium 
subovoid, narrowed and excavate basally, slightly 
upturned ventrally, transversely carinate dorsally, 
obliquely carinate laterally becoming longitudinally 
carinate medially. 
Distribution 
Known only from the Perth and Watheroo areas 
of Western Australia. 
Etymology 
The specific name is derived from the type 
locality. 
EXCLUDED SPECIES 
Macrothynnus ioleius Montet, 1922 
Macrothynnus ioleius Montet, 1922: 212; Given, 1954: 
47; Salter, 1954: 302. 
Remarks 
This species was described from a single female 
collected at King George Sound, Western Australia, 
and held in the Paris Museum. The holotype is 
identical to several females collected with, or 
mounted with, the males of Oncorhinothynnus 
xanthospilus (Shuckard, 1841) and is therefore 
considered to be a synonym of that species. There 
are no female types of O. xanthospilus. 
Montet's (1922) description of Macrothynnus 
ioleius is the only published description of the 
female of O. xanthospilus. 
DISCUSSION 
Macrothynnus is a small but distinct genus. It 
contains some of the largest Australian thynnines 
second only to Megalothynnus in size, and yet at 
least two species M. insignis and M. watherooensis, ) 
show atypical size variation in which some 
specimens are half the body length of others. This 
size variability is unknown in other Australian 
genera of the subfamily. Its cause is also unknown, 
but may result from a wide size range in acceptable 
host larvae, and may be apparent because of the ' 
large size of species in this genus. It may be more 
apparent in M. insignis and M. watherooensis due to 
better representations in collections compared to 
other species of this genus. 
At least one species, M. insignis, is associated 
with limestone deposits, and although not 
restricted to such areas, this species of 
Macrothynnus at least, may prefer host plants and/ 
or larvae found in calcium carbonate rich soils. M. 
insignis was common at Jewel Cave, but difficult to 
catch. The large size and therefore rapid flight of 
this, and other species of Macrothynnus, may 
explain the paucity of specimens in collections. 
ACKNOWLEDGEMENTS 
I thank the curators of the Institutions mentioned 
for the loan of the specimens in their care, and 
particularly Mick Day and Tom Huddleston for the 
loan of types. 
REFERENCES 
Given, B.B. (1954). A catalogue of the Thynninae 
(Tiphiidae, Hymenoptera) of Australia and adjacent 
areas. New Zealand Department of Scientific and 
Industrial Research Bulletin 109: 1-89. 
Montet, G. (1922). Thynnides nouveaux du Museum 
d'Histoire Naturelle de Geneve. Revue Suisse de 
Zoologie 29:176-226. 
Salter, K.E.W. (1954). Studies on Australian Thynnidae. 
1. A check list of the Australian and Austro-Malayan 
Thynnidae. Proceedings of the Linnean Society of New 
South Wales 78: 276-315. 
Salter, K.E.W. (1958). Studies on Australian Thynnidae 
Shuckard, 1841 (Hymenoptera). III. An introduction 
