1927] Observations on Wood-boring Insects 89 
basis of wing venation and many anatomical structures it seems 
probable that the families Xyelidae and Pamphiliidae represent 
the most primitive type related to forms from which the present- 
day Sawflies (Tenthredinidae et at.) have been derived. They as 
well as the sawflies are typically associated with trees although 
they are leaf-feeders and notxylophagous. From them also pro- 
bably have come the wood-wasps, typified by the very general- 
ized Xiphydriidae and the Siricidae. From a paleontological 
standpoint the Siricidae might appear to be the oldest Hyme- 
noptera as the only clearly preserved members of the order 
known before the Tertiary are some upper Jurassic Siricidse that 
occur in the Solenhofen lithographic stone . 1 This is very scant 
evidence, however, and indicates only a lack of knowledge as 
the early Tertiary, especially the Lower Oligocene sees the II y- 
menoptera as diversified and almost as modern in type as at the 
present day. Nevertheless, the Siricidse clearly represent the 
remnants or offshoot of a group which gave rise to an important 
and extensive series, the Parasitic Hymenoptera, which include 
a considerable number of families and a vast number of genera 
and species. The parasitic habit is first manifest in the entomo- 
phagous Oryssidse and in them we find still an association with 
wood boring insects, as Oryssus is known regularly to live in 
wood and has recently been found to be an ectoparasite of beetles 
belonging to the family Buprestidae. The Oryssidae have been 
considered as forming an independent superfamily, but most hy- 
menopterists agree in associating them with the Siricidae. There 
can be no reasonable doubt that they have arisen from the 
siricoid stem, as well as that they represent the most primitive 
parasitic group in the order. Among the other parasitic Hy- 
menoptera, the Aulacidae (exclusive of Evania and its allies) 
show a number of similarities to the Oryssidae of such nature 
that we must consider them related, and as the Aulacidae are 
the most primitive of the Ichneumonoidea we find this vast 
group clearly brought forth by xylophagous ancestors. The only 
other group of Icheneumon-flies that retains the costal cell which 
disappears in the higher forms, is the Stephanidae. Little is 
known of their habits, but their association with trees leaves 
^ee footnote on page 87. 
