Some Inhabitants of the Round Gall 

 of Golden rod 



BY cm PING, ITHACA, N. Y. 



Introduction. — The round gall growing on the stem of goldenrod 

 is the home of several insects, including, besides the gall maker 

 itself, Eiirosta solidciginis Fitch, a number of inquilines and para- 

 sites. The fly larva starts its work on the young shoot of goldenrod 

 during the last part of the spring, when the plant is about 2 or 3 feet 

 high. It spends the greater part of its lifetime, including both 

 the larval and pupal stages, in the gall. The larva may carry a para- 

 site in at the time of its own entrance, in which case the latter will 

 eat up its host and live inside the gall until the following spring. 

 After the gall has started to grow, other insects which are harmless 

 to the gall maker may get in too; they, however, do not penetrate 

 into the central cavity, but simply make their dwelling in the com- 

 mon parenchyma of the walls of the gall. Most common of these 

 is the mordellid beetle, Mordellistina iinicolor Lee. 



The galls are round and hard, with surface almost smooth when 

 fully developed. The punctures made by the entrance of the inhab- 

 itants are not seen at all after the galls become mature. The struc- 

 ture on the surface does not show much difference from other parts 

 of the stem, but sometimes the surface is fissured, due to the crack- 

 ing of the epidermis. Rosin is often found on the surface of the 

 galls, and on opening the galls a number of well filled rosin pores 

 will always be found in the swollen common parenchyma. In the 

 central pith a chamber is found in which lives the larva. Doubtless 

 the rosin in the wall is highly protective against foraging birds and 

 mammals, yet occasional galls will be found in late season drilled 

 by woodpeckers or gnawed open by small rodents. 



To the completion of this paper, I desire to express my gratitude 

 to Dr. J. G. Needham of Cornell University, by whose suggestion 

 and under whose supervision this work was carried on. His con- 



