188 MR. LUBBOCK ON TWO AQUATIC HYMENOPTERA. 
We have heard much lately about the “imperfection of the Geological Record ;" and 
all geologists admit the fact, though they may differ as to the degree. But what shall 
we say for the Zoological Record ? What terms shall we find strong enough to express 
our ignorance of existing animals? Ispeak not now only of foreign species; even in our 
own country how imperfect is our. knowledge even of the Vertebrata! During the last 
year, two new reptiles and two new fishes have been added to the catalogue; descending 
to the Invertebrata, however, the case becomes far more striking. Many groups, indeed, 
have been almost entirely neglected by our naturalists; but, even of those which have 
been comparatively popular, how little is known! For instance, the Hymenoptera have 
many admirers, and are carefully studied. Any entomologist happening to see a 
Hymenopterous insect in the act of swimming would have been well aware that he had 
a novelty before him; yet the fact that such a creature exists has until now escaped 
observation. Does not this show how imperfect is our knowledge ? 
As I have referred to paleontology, permit me to say, in conclusion, that if Polynema 
natans and Prestwichia aquatica had been extinct species, no paleeontologist would have 
suspected that they were aquatic; in the present state of our knowledge, there is 
nothing in their structure which would have suggested such an idea. 
Mr. Darwin (* Origin of Species,’ p. 184) has brought together several instances of the 
same fact, but not one, I venture to think, which is more remarkable. 
POLYNEMA NATANS, n. S. 
Male black. 
Female black; legs, eight basal segments of antenne, posterior part of thorax, and 
peduncle ferruginous. | 
Length of female ‘038 of an inch; of male :042. 
In a weedy pond; from the beginning of August to the end of September. 
The antennze are in the male as long as the body, and consist of twelve segments; the 
basal segment is about twice as large as the others, which do not differ much in size; 
the second is somewhat pear-shaped; the nine following are cylindrical, abruptly trun- 
cated at the apex, tapering at the base; the terminal segment tapers slightly to the 
apex, which is rounded. They are clothed by short, black hairs, which have somewhat 
the appearance of being in whorls. 
The antennz of the female are shorter, being only :022 in length. They consist of 
nine segments ; the first two are like those of the male ; the following six are smaller and 
more pear-shaped; the last is rather smaller at the end, and club-shaped. The arrange- 
ment of the hairs is the same as in the male. 
The anterior legs are of moderate size, and consist of the usual parts. The coxa is 
broad at its base, and gradually diminishes to the apex; the trochanter is cylindrical; the 
femur is elongated, and somewhat swollen in the middle; the tibia is long, cylindrical, 
and increases slightly towards the apex; the tarsus is four-jointed, the two middle seg- 
ments being somewhat smaller than the first and last. The foot consists of two claws 
and a central membranous expansion. The hairs on the leg are short, black, and 
arranged as in other allied species. 
