The genus Monoctenus is represented in the United States and Canada by three 
species, all of which occur in eastern North America on Juniperus spp., and Thuja 
spp. None is considered a serious pest of forest or shade trees. M. suffusus 
(Cresson) and M. fulvus (Norton) occur in southern Canada and in the Northeastern 
States west to Kansas. Their hosts are redcedar, northern white-cedar, and juniper. 
Full-grown larvae are dull green and about 18 mm long. The head is light brown: 
the body is marked with three, dark longitudinal stripes: and the legs are black. 
Adults appear in May, and larvae are active during June and July. 
The genus Neodiprion contains more than 30 species in North America (697). 
Many of the most destructive species of sawflies are in this genus. Outbreaks of 
several species have occurred, resulting in serious damage to young pines on 
thousands of hectares of pine plantations in the Eastern United States, and some- 
times spreading over thousands of hectares of forested areas before subsiding. 
Several authors have discussed the taxonomy of the genus (30, /042). A list of 
world species and their distribution is available (/099). Life cycle information, in 
addition to preserved specimens of reared adults and feeding larvae, is often needed 
for positive identification of Neodiprion sawflies (697). 
The redheaded pine sawfly, NV. /econtei (Fitch), occurs in southeastern Canada 
and throughout the Eastern United States. Its preferred hosts are jack, red, short- 
leaf. loblolly, slash, longleaf, pitch, and Swiss mountain pines. Eastern white pine, 
larch, deodar cedar, and Norway spruce may also be defoliated, especially where 
they are growing close to trees of preferred species. Full-grown larvae are about 20 
to 30 mm long. The head is reddish and the body is yellowish white, with six rows 
of black spots (fig. 179). 
Pupation occurs in early spring and the adults appear in a few weeks. Eggs are 
deposited in the tissues of current or previous year’s needles, a single female 
depositing up to 150 eggs. The larvae feed gregariously on new and old needles and 
also on the tender bark of young twigs. Sometimes they completely defoliate a tree, 
progressing from the top downward, before they reach maturity. When this hap- 
pens, larvae may abandon the tree and migrate for distances of several meters in 
F-532021 
Figure 179.—Larvae of the redheaded pine sawlfly, 
Neodiprion lecontei, on loblolly pine. 
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