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 he concluded in our next.) 



ON A NEW SPECIES BELONGING TO THE EPHEMERIDEOUS GENUS 

 OLIGONEUBIA (0. TBIMENIANA). 



BY B. M'lACHLAN, F.L.S. 



The genus Oligoneuria was founded in 1843, by Pictet, on a curious 

 insect (0. anomala) 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 j3or excellence are " day-flies," a term 

 which, when applied to most EpTiemeridce, is erroneous. But truly 

 Oligonewria, judging from its European representative, is destined to 

 enjoy (iu 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?). 



Sal. 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 margiaed with blackish, a line of which colour is 



