28 PHILOSOPHICAL TRANSACTIONS. [aNNO J 750. 



An Extraordinary Case of a Fracture in the Arm. By Mr. John Barde, Sur- 

 geon in New York. Covimunicated by Mr. John Frehe, F. R. S., Surgeon to 

 St. Bartholomew's Hospital. N" 4Q4, p. 397. 



This fracture occurred to a lady about the 3d month of her pregnancy, in 

 consequence of which the bones did not unite until 9 days after her delivery. 

 From that time, in less than a month, the callus was entirely confirmed, and the 

 patient recovered the use of her arm. This case, (adds the author,) is similar 

 to 2 cases related by Hildanus, in which the formation of a callus, was retarded by 

 pregnancy. 



A further Account of the Libella* or May-flies, from Mr. John Bar tram of 

 Pennsylvania, communicated by Mr. Peter Collinson, F. R. S. N° 494, p. 400. 



The May-flies of America have no very remarkable difference from ours ; 

 excepting a few days in the fly state, they live all the year a water insect. Their 

 bodies being replenished with an oily matter, they easily quit their husks, and 

 rise up to the surface of the water, and disperse themselves a mile or more back 

 in the woods, while others stay near the water. 



May the 4th 1749, Mr. C. perceived many had attained wings, and were 

 very thick spread on the bushes and grass, by the river sides. The second day 

 after their leaving their aquatic abode they cast another skin, after which their 

 tails are longer, and their wings drier, and more transparent. The 5th and 6th 

 was rainy, the 7th windy ; so very few came out. The 8th was cool ; so few 

 were seen : but the 9th and 10th, being warm, many swarmed late in the 

 evening; and the Uth, 12th, 13th, they swarmed abundantly. What he calls 

 swarming, was their gathering thick as bees, near the rivers, to lay their eggs 

 in the water. 



In their flight they mount to the tops of trees, 20 or 30 feet high : their 

 motion is surprizing, hovering up and down, rising and falling, 7 or 8 feet at a 

 time: this he takes to be the time and manner of their impregnation. After which 

 they fly to the brooks, cast out their eggs, and perish immediately : their eggs 

 sink directly to the bottom, and lodge among the mud and gravel, and may be 

 food for some minute water animal. From their eggs proceeds a deformed grub, 

 which subsists under water, and is food for eels, till next season, that it attains 

 its fly state, and then is food for fish and fowl. It is remarkable, the males are 

 black, and live several days after the females. 



The reason of their being so long in coming forth this year was, the cold 

 chilly weather : other years, in a warm season, in five days they would have per- 

 formed all their functions, and disappeared. 



We have two other smaller kinds, which very much resemble the former, 



* See page 290 of volume ix. 



