petioles of maple leaves. The larvae tunnel in the petioles, usually breaking them 
near the leaf blade, and the leaves fall (fig. 197). After the petioles break, the larvae 
continue to feed for about | 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. 
Courtesy Conn. Agric. Exp. Stn. 
Figure 197.—Petiole of maple leaf severed by larvae of 
the maple petiole borer, Caulocampus acericaulis. 
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 during the summer. 
The brownheaded ash sawfly, Tomostethus multicinctus (Rohwer), occurs in 
southern Canada and throughout the Eastern United States west to the Great Plains, 
and also in Oregon and California. Its hosis 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 cocoonlike cells in the topsoil. 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 
voracious feeders that a heavily infested tree may be completely defoliated in | 
week. Shade trees are especially subject to serious defoliation (7/3). 
The blackheaded ash sawfly, Tethida cordigera (Palisot de Beauvois), occurs 
throughout much the same area as the brownheaded ash sawfly, except Oregon and 
California. The habits, food plants, and life histories of the two species are also 
very similar. Full-grown larvae are whitish with a yellowish tinge and are about 18 
mm long. The head is shiny black, and the thoracic legs are eae brown. This 
species 1s occasionally a pest of shade trees. 
408 
