1915 ENTOMOLOGICAL SOCIETY. 19 



The gall consists of the enlarged petiole of the leaf. The leaves infested are 

 borne on the branehlets from which the pistillate catkins spring. 



In this vicinity only a few examples of the host plant occnr, but all of these 

 seem to be infested with the gall. 



Pontania crassicornis Eohwer. 

 Host, Salix humilis Marsh. 



The gall resembles the well known Pontania pomwn, Walsh, in shape, but is 

 considerably smaller. It is densely pubescent and several are usually crowded 

 together on one leaf. 



Pontajiia desmodiodes Walsh. 

 Host, Salix liumilis Marsh. 



A smooth, flattish gall with a semicircular outline originatiiig from the 

 mesophyll of the leaf of the host. 



The last two galls mentioned are abundant in this locality. 



Especially in the western part of the city the numerous ridges and plains 

 consist largely of sand sorted over and deposited by the wave action of the glacial. 

 Lake Iroquois. In the light soil thus produced pines and oaks flourish and in 

 the open spaces among these Salix liumilis ilnds an ideal habitat. The resulting 

 frequent occurrence of this food plant contributes to the abundance of several of 

 our sawfly galls parasitic on this host. 



Poniania hyalina Norton. 

 Host, Salix all a L. 



The galls are arranged in two almost parallel rows, one on each side of thei 

 midrib of the leaf. 



This is the most plentiful willow gall in this vicinity. The host has been 

 planted in large numbers and few of these escape infection. 



Poniania lucidce Eohwer. 

 Host, Salix lucida Muhl. 



The gall is produced as an enlargement of the petiol-e or midrib of the leaf. 



Throughout the district in general thi's species is not common. 



Pontania pisum Walsh. 



Host, Salix discolor Muhl. 



An almost spherical pea-like gall, with a small point of attachment to the 

 leaf of the host. 



Only rarely found in the locality. 

 Pontania pomum Walsh. 



Host, Salix cordata Muhl. 



A large globular gall originating from the leaf of the host. It is greenish- 

 yellow in colour usually with a rosy tint on one side. 



Among the numerous sand ridges, referred to previously, are many streams 

 and ponds of water. These are skirted, often for long stretches, by a screen of the 

 heart-leaved willow. The majority of these host plants are always infested with 

 this gall. 



The President: The heartiest thanks of the Society are due to Dr. Cosens 

 for his excellent report, full as it is of the most valuable original observations 

 which should form the basis of considerable further work, and be a very welcome 

 contribution to our Proceedinsrs. 



