191 2] Morphology and Biology of Insect Galls 343 



This species is spherical in form and has an epidermis covered with 

 a short dense pubescence that gives a felty appearance to the exterior of 

 the gall. A fibrous mass of ceils surrounds the centrally placed larval 

 chamber. Colour gray turning darker when dry. Individuals of this 

 species are so numerous that the ground, under the trees infested by 

 them, is often covered thickly with galls. 



Dimensions: — ^Average diameter 8 mm. 



Outside the nutritive zone is a wide crystal layer, each cell of which 

 is completely filled with a crystal mass. The sclerenchyma of the pro- 

 tective zone is formed in a very unusual manner. The sides of contiguous 

 cells are thickened in such a way that there is an almost spherical deposit 

 at the points where the cells are in contact. 



Radiating out from the protective layer are long narrow cells which 

 form the minor part of the parenchyma zone. The remainder of this 

 zone consists of irregularly elliptical, thin-walled cells. The epidermis 

 is covered with a dense growth of trichomes with thick laminated and 

 sclerified walls. 



Amphibolips confluens Harris. 

 Host Quercus coccinea Muench. 



A monothalamous gall attached to the petiole or midrib of the leaf. 

 The midrib is never continued beyond the point of origin of the gall. 



Globular to prolate spheroidal in shape and invariably terminating 

 in a minute point. The thick walled larval cell at the centre of the gall 

 is surrounded by a sponge-like mass of fibres that is at first white but 

 becomes dark brown when the gall is dry. At a very early stage of de- 

 velopment the epidermis of the gall is pubescent but later it becomes 

 smooth. The colour is at first green but this changes to a lustrous light 

 brown when the gall is old. 



Dimensions : — Average diameter 40 mm. 



(a) Stage in which the gall is 2 mm. in diameter. 



Almost the entire gall consists of a compact tissue, which is composed 

 of small uniform cells. Lines of narrow elongated cells, however, pass 

 in a radial direction throughout this tissue. These cells do not extend 

 into the gall cavity nor out to the epidermis, they traverse about two- 

 thirds of the gall radius. As they approach the epidermis the lines curve 

 around and run parallel to its surface. Spiral vessels are in some cases 

 differentiated in these rays and the elements are more numerous near 

 the point of attachment of the gall. 



(b) Older stage 9 mm. in diameter. 



The gall wall can now be divided roughly into three sections. That 

 part lying next the larval cell resembles closely the compact tissue de- 

 scribed in the preceding stage, except that immediately adjoining the 



