66 MR. J. LUBBOCK ON THE DEVELOPMENT OF 
the appendages, while in Phryganea and some other insects the reverse appears to be. 
the case; and we shall even find in the same species minor variations in the relative 
development of different organs. 
The Development of Chloéon. | 
With these few introductory observations, I will pass on to consider the development 
of the larvee of Chloéon dimidiatum*, which are very common in our Kentish ponds. 
- They have not escaped the notice of previous observers, but I am not aware that either 
they or any other insects belonging to the homomorphous series have ever been watched 
through their various changes. The development of the Ephemeridz is thus described 
by Pictet + :—‘ Les métamorphoses sont incomplètes. Les larves vivent dans l'eau, 
s'abritant dans la vase ou sous les pierres. Elles rappellent plus ou moins la forme de 
Vinsecte parfait, sauf qu'elles manquent d'ailes, qu'elles sont plus fortes, que leur bouche 
est mieux armée, qu'elles ont toutes trois soies caudales, et que leur abdomen est muni 
sur ses côtés d'organes respiratoires externes de forme variable. La nymphe, agile 
comme la larve, n'en diffère que parce qu'elle porte des rudiments d'ailes." Prof. West- 
wood, again, says that the larvse differ from the pupse “only in the absence of rudimental 
wing-covers;" and other naturalists have, I believe, but repeated this statement. 
First State (Pl. XVII. fig. 1). 
The smallest specimens which I have seen were only ;8;ths of an inch in length, 
quite colourless and transparent. Not having hitherto had an opportunity of breeding 
the insect from the egg, I am of course unable to state whether this is really the con- 
dition in which the young Chloéon leaves the egg; but for the present I shall, for 
convenience, assume that it is so. The head is shaped somewhat like a capital A, and 
is gjoths in width. The eyes are five in number, round, and equal in size. Two 
are situated on the posterior angles of the head; two are in front, and somewhat 
further apart, so that, being placed on the sloping side of the head, they look elliptie; 
though in reality round. The fifth, which perhaps is normally composed of two, lies 
more in front and in the middle line. The general appearance of all five is similar; 
and 1 could see no trace of any facets. 
The antenn (fig. 18) are ẹẹsths in length, and consist of thirteen segments. The 
first is short, and tapers from the base to the apex; the second is also short, but tapers 
in the opposite direction, i. e. from the apex to the base. The third segment is long 
and cylindrical ; it has two or three hairs near the apex. The four following segments 
are together about equal in length to the third ; the divisions between them are, however, 
but slightly marked, and the seventh only has the usual hairs at the apex ; so that it may 
be doubted whether it would not be perhaps more correct to consider this division of the 
antenna as constituting only a singlesegment. The same description applies to the four 
following segments; the twelfth tapers to the apex, and bears a fine, needle-like body, 
which might be called a seta almost as well as a segment. 
۰ The. name has been kindly determined for me by my friend Mr. F. Walker. 
-t Histoire naturelle des Névroptéres: Ephémérines, p. 5. 
