Insect Galls. 7 



Within galls may sometimes be found parasites or inquiliues. The 

 former, preying directly upon the gall-maker, causes its death, but not 

 until its growth is nearly or quite complete. The inquilines are merely 

 guests within the gall, profiting by the food supply and by the protection. 



Aside from the collection of the galls of different localities, and the sub- 

 sequent summary of their distribution, two very interesting questions 

 suggest themselves for investigation. First, are these malformations the 

 result of chemical or of mechanical action ? Second, of which of the 

 American gall-makers is it true that there is alternation of generations? 

 The classification of gall-insects will undoubtedly be somewhat altered 

 when this question is answered. Either line suggests a fascinating series 

 of observations and experiments for the one undertaking it. 



My thanks are especially due to George Dimmock, Ph. D., for sug- 

 gestions in preparing this paper, for use of publications not otherwise 

 available and for reading the manuscript. Also assistance has been 

 rendered by Mrs. Anna D. Nash in preparing some of the photographs. 



PLANT LIST. 



A list of the plants upon which the galls described in this bulletin 

 are found. 



The plant names are in accordance with Britton's Manual of the Flora 

 of the Northern States and Canada . . . . 1907. See Systematic index 

 for family to which gall-insect belongs. 



PIN ALES. 



PINACEAB. 

 Pinus rigida. 



Diplosis rigidae Packard. Pitch-pine needle-gall. 



Diplosis pini-rigidae Packard, 10th ann. rept. U. S. geog. and geol. surv. terr. f. 1876, 1878, p. 



527, fig.; 5th rept. U. S. ent. comm., 1890, p. 798-800, fig. 271. 

 Cecidomyia resinicola Aldrich, Cat. N. A. dipt., 1905, p. 160 (following KertOsz ) 



This gall consists of an enlargement at base of cluster of needles. 

 The base of each is widened and curved so as to form one spherical 

 chamber within which are several smaller ones, apparently in pitch. The 

 diameter of the galls is about 5 mm. The needles, stunted in growth, 

 are from 1 to 2 cm. long. On pitch pine, Pinus rigida. 



