small groups of trees, especially trees growing more or less in the 
open. Twigs supporting large webs sag badly. 
Other species of Jchthyura frequently encountered are J. albo- 
sigma Fitch on aspen; and I. apicalis Wlkr., I. brucei Hy. Edw., 
and I. strigosa Grote on aspen and willow. None are very impor- 
tant. 
The yellow-necked caterpillar, Datana ministra (Drury), occurs 
in southern Canada and throughout most of eastern United States. 
Its food plants include many species of fruit, shade, and forest 
trees. Important forest and shade tree hosts include white and 
yellow birch, basswood, elm, oak, maple, butternut, walnut, 
mountain ash, hop hornbeam, and honey locust. The adult has a 
wingspread of about 50 mm., and its forewings are cinnamon- 
brown, marked with irregular dark lines. Full-grown larvae are 
about 50 mm. long and are moderately clothed with long, soft, 
white hairs. The head is jet black; the prothorax, bright orange- 
yellow; and the body is marked longitudinally with alternate 
yellow or whitish and black stripes. 
Adults appear during June and July. Eggs are laid in masses 
of 100 or more each on the undersides of the leaves. The larvae 
feed in colonies (fig. 116.) near the ends of twigs and branches. 
When disturbed, they elevate both ends of the body. At maturity, 
they drop to and enter the soil to depths of 2 to 4 inches where 
they pupate and spend the winter. There is one generation per 
year. 
Damage is seldom serious in the forest, although heavily in- 
fested trees may be completely defoliated. Fruit, shade, and orna- 
mental trees are injured most severely. Two species of tachinid 
parasites, Compsilura concinnata Meig. and Winthemia datanae 
Town. are important natural enemies. 
Datana angusi G. & R. feeds on hickories, oaks, beech, gray 
birch, and butternut and occurs throughout eastern United States, 
west to Illinois, and along the north shore of Lake Erie in On- - 
tario, Canada. Full-grown larvae resemble those of D. ministra, 
but differ in having an entirely black cervical shield. 
COURTESY ILL. NAT. HIST. SURV. 
FIGURE 116.—Cluster of lar- 
vae of the yellow-necked 
caterpillar, Datana min- 
istra, 
oll 
