84 On the perfect State of Prosopistoma punctifrons. 
very short and abundant hairs; the latter character occurs in all 
the subimagos of Ejphemerina. 
Setee.—The sete (fig. 17) are far from showing the same com- 
plication of structure in the perfect insect as in the nymph. 
They are borne by the last segment, in the cavity of which they 
canno longer shelter themselves, the apparatus destined to make 
them enter into the interior of the body having become atro- 
phied, because, in the perfect state, it would be of no use to the 
insect to retract them; the last joint can still, however, in 
part withdraw itself into the ninth. We no longer observe 
traces of annulation on the surface of the sete: ; and the hairs 
which clothe them are very short and very irregularly ar- 
ranged. 
I have carefully dissected the only two examples of the sub- 
imago that I have been able to procure. Both of them being 
females, I found in the interior of their visceral cavity a great 
quantity of eggs (about sixty in each). ‘These eggs (fig. 5) were 
about ! millim. in length; their form was distinctly ellipsoidal ; 
their surface presented a multitude of pretty strong rugosities, 
into which the vitelline mass penetrated (fig. 6); and their 
colour was milk-white. ‘These eggs, from their general ex- 
ternal characters, and especially the absence of the hood or 
cap at their two extremities, greatly resemble those of Cloé 
diptera. After having freed the visceral cavity of all the 
eges, I observed the empty state of the digestive tube and the 
atrophy of all the glandular organs of that apparatus, which 
had either completely disappeared, like the yellow hepatic 
layer of the stomach, or partially, like the Malpighian tubes. 
The nervous system presented the same degree of concen- 
tration as in the nymph. It consisted of a pair of cerebroid 
ganglia, a cordiform subcesophageal ganglion, and a single 
large thoracic ganglion representing the whole of the ventral 
chain. 
The tracheal apparatus consisted of two lateral trunks, 
sending forth numerous ramifications to all parts of the body, 
and connected with the four or five pairs of stigmatic aper- 
tures by means of very short secondary trunks. 
As the perfect state of Prosopistoma punctifrons is now 
known, my collaborator, Dr. H. Joly, and myself intend 
changing the name of the animal, in order to conform to the 
entomological usage according to which the denomination of 
an insect should not be derived from a larval character, as is 
the case with Prosopistoma; and it is in the monograph of the 
genus, which we shall not delay to publish, that the definitive 
diagnosis of this Hphemerine under its new denomination 
will be found. 
