542 MISC. PUBLICATION 657, U. S. DEPT. OF AGRICULTURE 
The larval forms of this order show considerable variation. Those 
of the sawflies, with the exception of the leaf-mining and wood-boring 
species, resemble caterpillars, having a distinct head with a pair of 
ocelli, well-developed thoracic legs, ‘and usually abdominal pro-legs. 
They are generally independent in habits, being mostly free-living 
and phytophagus, whereas those of the other groups (bees, wasps, and 
ants) are more like maggots, being legless and somewhat helpless, and 
are dependent on being fed or being placed i in or on their host insects. 
This order has been divided systematically into two suborders, as 
follows: The Chalastogastra, comprising the sawflies and horntails; 
and the Clistogastra, which includes the ants, bees, wasps, and other 
forms. Viereck (422) in his Hymenoptera of Connecticut gives a good 
treatment of the order. 
Suporper CHALASTOGASTRA or SYMPHYTA 
THE SAWFLIES AND HORNTAILS 
By J. V. SCHAFFNER, JR., AND WILLIAM MIDDLETON 
The suborder Chalastogastra includes the more generalized forms 
and the adult is characterized by having the abdomen joimed to the 
thorax in a broad union, in contrast with the constricted waist or 
slender basal segment of the abdomen in the Clistogastra. The vena- 
tion of the wings, although displaying a great many differences, is 
less reduced than in the other suborders. There are no wingless forms. 
The antennae, which differ greatly in shape and number of segments, 
are always inserted between the eyes above the base of the clypeus 
and have their bases exposed. Each female has a complicated ovi- 
positor. In some species it is adapted for boring holes in trees; in 
other species it consists of two pairs of sawlike plates protected by a 
sheath. 
The larvae of this suborder are all plant feeders, but unlike the 
larvae of the Lepidoptera each possesses a single pair of ocelli, one on 
each side of the head. They frequently have six or more pairs of 
fleshy leglike structures on the abdomen, called prolegs, none of which 
1s provided with hooks or “crochets,” whereas in the Lepidoptera there 
are never more than five pairs of prolegs and all are provided with 
crochets, except that in the Family Megalopygidae there are seven 
pairs of prolegs, those on the second and ‘seventh abdominal segments 
without crochets. 
This group of insects is very difficult to classify and needs much 
further study. The separation of the adults into species is rather 
difficult, because there is frequently considerable difference between 
the two sexes. There are many species in the 11 families of this sub- 
order represented in the Eastern States, but comparatively few of 
them are serious pests of the forest and shade trees in this region. 
Some of the more important species are of foreign origin. 
In the following discussion only species known to be of importance 
are treated in detail. As the injury is caused by the larvae, and this 
is the stage most commonly encountered by those persons responsible 
for the care of trees, the greatest emphasis is placed on the characters 
of the larvae, their food plants, and their habits. 
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