History of British Entomostraca. 321 
ject.* That he is wrong cannot be doubted, I imagine, and there 
is every reason to presume, that their being carnivorous serves a 
most useful purpose in the economy of nature. The adults in their 
turn fall victims to, and are devoured by, other insects, the chief of 
which are the Hydrachnae, Hydrae, and larvae of aquatic insects, 
which destroy them in such vast numbers, as in some measure to 
counterbalance the most extraordinary fertility which they possess, 
and which I have already mentioned above. 
Species. 
A. Fresh Water Species. 
1. Cyclops quadricornis Plate VIII. Fig. 1,1-14 Specific character An- 
tennis longis ; corpore ovato ; cauda recta bifurcata ; furca utraque setis 
quatuor plumosis instructa ; ovariis externis duobus. 
Synonimes, Sfc. Cyclops vulgaris, Desmarest, Considerat. generates sur les 
Crustaces, p. 362. 
Monoculus quadricornis, Jurine, Hist, des Monoc., &c. 1820, pp. 1-49. 
Plates 1, 2, 3 Figures excellent. 
Cyclops quadricornis Ramdohr, Beyt. zur Naturg. einigen deutschen Monoc- 
arten, 1805. Pp. 1-6, t. 1, fig. 1-10 ; t. 2, f. 1, 3. 
Cyclops quadricornis Mutter, Entomostraca, &c. p. 109, tab. 18, fig. 1-4, 
1785. Figure pretty good. 
Nauplius saltatorius, (the young in its first state,) Mutter, Entomost. p. 40, 
tab. 1. fig. 3-7. 
Eichhorn, Beytrage zur Naturgeschichte dar Kleinsten Wasserthiere, p. 54, 
tab. 5, fig. m. n. 1781. Very bad figure. 
Le Monocle a quatre comes, De Geer, Memoires pour servir a 1'histoire des 
insectes, torn. 7, p. 483, plate 29, fig. 11-12, (adult insect,) plate 30, fig. 
5-9, (egg and young,) 1778. Figures not quite correct. 
Monoculus quadricornis, Fabricius, Systema Entomologiae, p. 295, 1775. 
Der Naturforscher, Stuck 5, p. 247, 1775. 
Neue Mannigfaltigkeiten, i. p. 640, fig. 3, 1774. Figure apparently copied 
from Roesel. 
Le Monocle a queue fourchue, Geoffroy, Hist, abreg. des Insectes, Vol. ii. 
p. 656, No. 3, plate 21, fig. 5, 1764 A very bad figure. 
Pediculus aquaticus, Baker, Employm. for Microsc. p. 383, pi. 15. fig- 1-4. 
1764.* 
Monoculus quadricornis, Scopoli, Entomologia Carniolica, p. 413-1139, 
1763. 
Monoculus Apus, Poda, Insecta Musei Graecensis, p. 125, tab. I. fig. 11, 12, 
1761. f 
* Geoffrey also says, that all the Monoculi live upon vegetable matter alone, 
Hist, abreg. des Insect. Vol. ii. p. 654. 
j- Baker's correspondent complains sadly of the figures which Leeuwenhoek 
gives, as being very incorrect, and yet the figures which he gives are ten times 
worse than Leeuwenhoek's ! ! 
$ The name of Mon. Apus is given incorrectly by Poda, as his figure, though 
very indifferent, is clearly that of the C. quadricornis. 
