54 V R. OSTEX SACKEN. 



breast-bone is hardly visible, as its front part only is horny, having the 

 appearance of a transverse, reddish-brown wavy line. The last abdo- 

 minal segment has several minute, fleshy-pointed projections. The 

 larva drops to the ground through the slit at a certain period of its de- 

 VL'l )pnieiit ; hence, empty galls are often found. 



Found ill considerable numbers in the Central Park, N. Y., in May, 

 1869. 



Contributions to the Natural History of the CYNIPID.E of the United Sta te 

 and their galls. — (Article 5th). 



BY R. OSTEN SACKEX. 



I.— New Observations on the Gall of CYNIPS QUESCTJS PALUSTRIS, 0. S. 



Among the oak galls described in my previous articles, one of the 

 most singular is the gall I named Cijnipa quercus palustris, from its 

 frequent occurrence on Q. palustn's, the pin-oak, although it is also 

 occasionally found on other oaks of the red-oak group. This gall is 

 especially remarkable on account of a small, cocoon-like body, contain- 

 ing the pupa, which rolls freely about in a comparatively large cavity, 

 without being connected in any way with the walls of this cavity, or, 

 in other words, with the substance of the plant upon which the gall is 

 growing. An examination of the shell of this cocoon-like body (which, 

 for brevity's sake, I will call ovule} proves that it does not consist of 

 animal, but of vegetable matter, in other words, that the ovule is not a 

 cocoon, although it contains the larva ami afterwards the pu])a. The 

 growth of these galls is so sudden that, although I have seen thousands 

 of them, I do not remember having seen one which was not full grown 

 as far as the size is concerned. Once or twice only I discovered spe- 

 cimens arrested in their growth by some unknown agency and withered 

 in that state; and in such specimens 1 observed the ovule still con- 

 nected, by a short stem, with the leaf or branch upon which the gall 

 was growing. It would seem, therefore, that the ovule is nothing but 

 the usual kernel, existing in many other galls, but which here, during 

 the growth of the gall, becomes disconnected from its shell. 



During my rambles in the Central I'ark, in New York, in May, 

 186'.), among numberless galls of this kind on tlie pin-oak, I observed 

 a good many which were double, that is, consisted of two galls sold- 

 ered together. Such galls instead of globular were oblong, sometimes 

 slightly narrowed in the middle. Usually, there was no partition on 



