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Psyche 
[April 
little doubt that they are parasites of wood-boring insects. The 
same is true of the peculiar family Megalyridse known only from 
Australia and South America and representing an archaic type 
most likely another derivative of the Siricoids. Among the two 
dominant present day families of ichneumon-flies, the Ichneu- 
monidse and Braconidse we find the more primitive smaller 
groups of each to be parasites of wood-boring insects, e. g. the 
Rhyssini of the former family and the Spathiinse, Hormiinse and 
Helconinse of the latter. Several other families have similar 
habits but these are much more highly specialized types, except 
perhaps the remarkable genus Ibalia. This is usually considered 
to be an aberrant Cynipid but it shows affinities with the Siricidse, 
upon which it is parasitic, and is without question a relict of 
some primitive group. 
From the foregoing it is evident that the association of the 
orders Hymenoptera and Lepidoptera with trees, especially with 
the wood of the latter is clearly marked in the most primitive 
families, in fact we may be almost satisfied without further 
evidence that these two large and diversified orders arose as 
lignivorous forms. This can hardly be true of their earlier an- 
cestral type, the Mecoptera, nor of the more primitive Mecop- 
teroid derivatives, the Trichoptera. This forms strong contri- 
butory evidence that the Hymenoptera and Lepidoptera had an 
origin coincident with that of the modern ligneous flora. The 
origin of the Coleoptera at an earlier time before this flora had 
developed resulted not in an association of the more primitive 
adephagous beetles with trees, but in the appearance of the 
lignivorous habit in some of the most highly specialized Celeop- 
tera such as the Cerambycidse and Ipidse (Scolytidse). Some 
other families like the Buprestidse have similar habits, but they 
represent by no means the most generalized members of the order. 
With the Diptera the rather sparse occurrence of wood boring 
forms offers little suggestion that the earlier types may have 
been associated with trees. Obviously the degenerate mouth- 
parts of the larval dipteron are not well suited to chewing wood, 
even in the more primitive nematocerous forms and only oc- 
casional types have become dependent upon the woody flora. 
