19^ 2] Morphology and Biology of Insect Galls 



349 



the leaf. They correspond to the larval cells, varying from 3 to 7 in 

 number. 



Dimensions: — Length parallel to axis of midrib 10-15 mm. 



Although nearly mature specimens of this gall were sectioned, a 

 protective zone was not found. 



In this species each larval chamber has a canal related to it. In 

 this respect it resembles A. piger Bassett. A section of the gall at a very 

 early stage of development shows that the canals open into the larval 

 chambers. When the gall becomes older, each canal is blocked by two 

 plugs of sclerenchyma. One of these occupies the same position relative 

 to the larval chamber as in the two preceding species ; the other is formed 

 near the external opening. These masses of sclerenchyma are shown 

 in Fig. 47. Trichomes do not appear to be produced in the canals. 

 Rhodites muUispinosus Gillette. 

 Host Rosa hlanda Ait. 



A globular to ovoid polythalamous gall produced by the swelling of 

 the stem or branches of the host plant. Since the larval cells are arranged 

 around the stem axis at about the same distance from the periphery of 

 the gall, the abnormal swelling completely encircles the stem. 



The gall is reddish brown in colour and has its surface usually densely 

 covered with fairly stout prickles. 



Dimensions: — Average diameter 25 mm. 



The principal mass of this gall is formed from the cortex of the stem. 

 The larval cells are embedded in it and a common parenchyma zone is 

 thus formed. A well-marked protective tissue, composed of cells with 

 porous, sclerenchymatous walls, separates this parenchyma zone from 

 the nutritive tissue that lines each larval cell. 



The response of the gall epidermis to stimulation is shown in the 

 production of the numerous prickles that are so marked a characteristic 

 of this gall. Since the stem of the host is usually unarmed this feature 

 appears the more remarkable. 



Rhodites lenticularis Bass. 

 Host Rosa hlanda Ait. 



A monothalamous, lens-shaped, thin-walled gall produced in the 

 mesophyll of the leaf of the host. They sometimes occur singly but 

 usually several are located on one leaflet. They often are so crowded 

 that they lose their circular outlines. 



This gall projects chiefly from the under side of the leaflet. 



Dimensions: — Longer diameter 2-3 mm.; shorter diameter 1-2 mm. 



Since it is possible to trace a considerable part of the unaltered 

 mesophyll of the leaf along the upper surface of this gall, proliferation 

 must have commenced in the spongy parenchyma of the leaf. The 



