The striped alder sawfly, Hemichroa crocea (Fourcroy), prob- 
ably an introduced species, occurs from coast to coast in southern 
Canada and northern United States. Its hosts include various 
species of alder and occasionally birch. Full-grown larvae are 
yellowish and about 20 mm. long. The head is shiny black, and 
there is a dark brown subdorsal stripe on each side running from 
the second thoracic to the tenth abdominal segment. Two broken 
subspiracular stripes composed of blotches and dashes extend 
along each side to the ninth segment. 
Winter is spent in the prepupal stage in cocoons just beneath 
the surface of the soil. The cocoon is very thin-walled and is 
formed within a cell made by cementing together particles of soil 
and sand. Adults appear during late May and deposit their eggs 
in slits cut in the sides of the midrib on the undersurface of 
leaves. The larvae are gregarious and usually eat all but the mid- 
rib and larger veins of the leaf. They become full grown in July, 
and, during late July and August, adults of a second generation 
appear. Larvae of this generation are found during August and 
September. There are two generations per year. This species 
occasionally severely defoilates alder in the Lake States, North- 
astern States, and Canada. 
The maple petiole borer, Caulocampus acericaulis (MacGilliv- 
ray), an introduced species, is known to occur in the Northeastern 
States south to New Jersey. The larvae feed by boring into and 
tunneling the petioles of leaf stems of maple. Full-grown larvae 
are light yellow with light brown heads and are about 8 mm. long. 
Winter is spent in the larval stage in a cell 2 or 3 inches below 
the surface of the soil. Adults appear early in May and deposit 
their eggs near the bases of the petioles of maple leaves. The 
larvae tunnel in the petioles until they break, usually near the 
leaf blade, and the leaves fall (fig. 198). After the petioles break, 
the larvae continue to feed for about a week to 10 days in those 
portions of the petioles remaining on the tree. When these also 
break and fall, the larvae vacate them and enter the soil to 
pupate. There is one generation per year. 
Damage by the maple petiole borer is slight. Nevertheless, 
heavy infestations on valuable shade trees may be undesirable 
because of the presence of large numbers of dead leaves on them 
during the summer. 
The brown-headed ash sawfly, Tomostethus multicinctus (Roh- 
wer), occurs in southern Canada and throughout eastern United 
States west to the Great Plains. Its hosts are red and white ash 
trees. Full-grown larvae are greenish- or yellowish-white and 
from 14 to 20 mm. long. 
Winter is spent in the prepupal stage in cocoon-like cells in the 
top soil. Adults appear as early as April in the southern portions 
of its range and lay their eggs in slits cut along the outer margin 
of young leaflets, several eggs per leaflet. Young larvae chew 
holes in the leaflets, and the older ones consume them entirely. 
Larvae become full grown and move to and enter the ground by 
late May in the South. Farther North, they become full grown 
at progressively later dates. Pupation occurs in the spring and 
there is only one generation per year. The larvae are such vora- 
cious feeders that they may completely defoliate a heavily infested 
463 
P. 
