The redheaded pine sawfly, Neodiprion lecontei, is a pest of pines in ornamental landscapes, nurseries, and plantations. Adults emerge in spring and a second generation occurs in mid summer. Eggs are laid on many 2 and 3 needled pine species such as Jack pine, loblolly pine, and red pine. Sawflies are not flies and the larvae do not turn into butterflies. They are non-stinging herbivorous wasps. They can defoliate trees and bushes in the landscape. Since they are gregarious it is sometimes possible to prune off an infested branch and remove all the larvae. Management for sawflies is similar as for caterpillars though not all the insecticides will work so check the label. Horticultural oil is a good bet especially for small larvae. Formulations that contain azadirachtin or spinosad are also effective. For sawflies and caterpillars, management of full grown caterpillars is generally not warranted; the damage is already done and they are hard to kill.
For pictures of redheaded pine sawfly larvae and more information visit: http://ecoipm.com/