1868.] 177 
the force of circumstances, and attach their cocoons either to the jar, or 
on one of the leaves. 
The cocoon, however, so formed, is very different indeed from that 
constructed by the larva when at liberty to follow the promptings of 
nature. 
{To be concluded in our next.) 
ON A NEW SPECIES BELONGING TO THE EPHEMERIDEOUS GENUS 
OLIGONEURIA (0. TBIMENIANA). 
BY E. M'lACHLAN, F.L.S. 
The genus Oligoneuria was founded in 1843, by Pictet, on a curious 
insect (O. anoviala) from Brazil, the founder probably little thinking 
that a then undescribed form pertaining to the same genus (O.rhenana, 
Imhoff,) swarmed in certain restricted localities in Switzerland. This 
latter species (or one very closely allied thereto) has since been found 
in other parts of southern and central Europe. When in Paris a few 
years since I saw a third in the Museum of Natural History there, 
from Mexico, but neglected to make a description of it. Mr. Eoland 
Trimen lately presented me with a large species taken by him in Natal, 
which I here propose to describe as O. Trimeniana. 
The genus is above all remarkable for the abortive condition of the 
legs, these organs being so greatly atrophied, that they must be nearly 
useless for the purpose of locomotion. And, indeed, the genus would 
appear to consist of insects which par excellence are " day-flies," a term 
which, when applied to most Ephemeridce, is erroneous. But truly 
Oligoneuria, judging from its European representative, is destined to 
enjoy (in the winged state) a brief existence, the hours of which may 
be easily counted : and, as probably most of its short span of life is 
passed in the air, the defective legs can be of little consequence to it. 
Oligoneueia Teimeniana, n. sp. 
Testaceo-albida ; alis niveis vix griseo-tinctis, anticis venis longitu- 
dinalibus absque costa tribus, quarum secunda et tertia longe furcatis ; 
setis caudalibus fere aequalibus albis,ad apicem pubescentibus ( ? imago?). 
Sab. Natalia. Long. corp. 6'" ; exp. alar, 19'". 
Head and thorax whitish-testaceous : vertex longer than broad, 
sub-triangular, obtuse in front, with a median raised line extending 
from the posterior edge to near the front, where it joins a similar trans- 
verse line ; the anterior portion bears two large oval tubercles placed 
laterally and broadly margined with blackish, a line of which colour is 
