LEPIDÓPTEROS ARGENTINOS PRODUCTORES DE AGALLAS 133 



I ara induced to lay the following observations and the accompanying dra- 

 wing beíbre tbe Society, rather with a desire of drawing the attention of 

 tbose naturalista tothesubject wbo may visit the . countr.v from whence tbe 

 material s were brought, tban with any bope of being able to explain the 

 remarkable facts connected with tbe reconomy of tbe insect wbicb is the 

 object of tbose investigations. 



Mr. Howship, wbo flrst showed me the curious galls and presented me 

 with specimens, inibrmed me at the same time that they were collected by Mr. 

 Earle, wlio accompanied captain Fitzroy in the Beagle gun-brig : he forrad 

 them, I understánd, in December, on a spot fifteen miles to the west of Mon- 

 te Video, Rio de la Plata. The plant bearing the galls, which Mr. David 

 Don thinks may be a species of Gelastrus, forins a sort of imderwood shrab, 

 observed only in that part of the country. 



The branch represented at B (Píate XL) (1) shows the situation of two 

 galls : they are frequently smaller, and sometimes flve or six are clustered to 

 gether, but I have never seen more tban two issning from the same point. Tho- 

 se in tbe píate are wrinkled, owing, I suspect, to their having been in a young 

 state when gathered, for many of the examples are smooth. The galls arise 

 where the attachment of leaves or flowers is indicated, and are therefore 

 most probably produced by the transformation of the buds themselves. On 

 the side of the gall is a round aperture, with an operculum beautifnlly fit- 

 ted to it (fig. B., o) (2) which may be easely picked out with the point of 

 a penknife : this operculum is equally convex with the rest of the gall and 

 is of the same thickness with it, but the diameter of the inside is less than 

 that of the external surface, which forms a broader rim (fig. 12, o) (3). In 

 fig. 11, the operculum has been removed to show the orífice, round which the 

 margin is thickened and a little raised. At fig. 13 (4) a gall is divided longitu- 

 dinally, showing its texture and the interual cavity, with the aperture on the 

 opposite side, from which the operculum, has been removed. At fig. 14 (5), 

 another section is given to show the situation of & pupa that is attached by 

 its tail to the base, with its head cióse to the operculum, which of course gi- 

 ves way by a slight expansión or elongation of the pupa when the insect 

 is ready to hatch, and the skin is tlieu left sticking in the passage. 



Having explained the structure of these galls, it is necessary to observe 

 that many insects belonging to the order Hymenoptera have tbe power of 

 forming these excrescences ; one of wbicb, the Diplolepis Gallae-tinctoriae. is 

 well known as tbe fly causing the galls employed in the manufacture of 



(1) Remplacé ici par la photographie ligare 1 b. 



(2) Figure 16 a du préseut artiole. 



(3) Figure 16 b du present article. 



(4) Figure 16 c du préseut article. 



(5) Figuro 16 d du prósont article. 



