1881.] NATURAL SCIENCES OF PHILADELPHIA. 2t 



egg-shaped. They are separate from the rest of the gall, from 

 which they quite differ in appearance, and are of a firmer sub- 

 stance. In fig, 10, the gall is three-sixteenths of an inch in 

 length, of which the cell occupies two-thirds, that is, one-eighth 

 of an inch. The largest gall observed had an outside measure- 

 ment of three-eights inch long and the same across the top. In 

 one of the galls opened, I found an imperfect insect (imago), 

 which is identified b}' Mr. E. T. Cresson as of the genus Cynips, 

 a true gall-fl3^ The specimen would not permit further identifi- 

 tification. 



At the meeting of the American Association for the Advance- 

 ment of Science, held in 1880, at Boston, I had the pleasure of 

 presenting the substance of this paper to the Entomological 

 Section. My account of the extravasation of the galls, as above, 

 caused much comment, the result of which was to confirm the 

 accurac}' of the observation which had been challenged. Prof. 

 C. V. Riley, well known as an entomologist, declared upon his 

 own observations, that many galls exude saccharine matter, citing 

 among others, those of certain Phylloxerae on Hickory, one of 

 which he had named caryae-gummosa on account of the abundance 

 and stickiness of the exudation. Mr. H. F. Bassett, who has made 

 extensive and careful studies of galls, said that he had found 

 many species of galls visited by ants ^ 



Specimens of the oak-gall visited b}' Melliger were sent to Mr. 

 Riley, concerning which he sa.js : The gall is one that is found 

 quite commonly in the Rocky Mountain region on Quercus undu- 



^ American Entomologist, Dec, 1880. The following additional remarks 

 will be interesting in this connection : Mr. E. P. Austin remarked that 

 the chemical composition of sugar and woody fibre are the same, and that 

 sugar could be produced by conversion from woody fibre in the plant. Dr. 

 J. Li Le Conte said that he understood tannin to be a conjugation of gallic 

 acid and sugar. Mr. B. P. Mann suggested that some light might be 

 thrown upon this food-supply of the ants, by the nature of much of the 

 moisture which appears occasionally at night in great abundance on the 

 leaves and other portions of plants, and which is usually mistaken for 

 dew. This moisture, it is said, diflers from dew in being produced under 

 circumstances which would not account for the formation of dew, and in 

 containing a perceptible quantity of sugar. It is the ordinary watery ex- 

 cretion from the surface of the plant, which, under favorable conditions 

 of the atmosphere, collects in beads or in drops, instead of evaporating as 

 rapidly as it is formed. 



