396 Mr. Brightwell on the Food of Corethra. 
Art. LIV. On the Food and Habits of certain Insects. 
By T. Baieutwe ct, Esg., F. L. 8S. 
Sustentatio larvarum, imprimis rapind viventium, sepius singularis. 
PABRICIUS. 
I, Reaumur has investigated and described the metamorphoses of 
the Corethra plumicornis,* a little Gnat of the family of the Tipulide, 
but this distinguished Naturalist was unable to determine the food of the 
larve ; he conjectured that they devoured the invisible animalcula, 
teeming around them in the stagnant waters which they inhabit. 
Reaumur found the darva in July and August in water. He describes 
its body as transparent, almost cylindrical, largest at its anterior part ; 
the head has in front a double hook (crochet). In the anterior part are 
two reniform little bodies, and two others of the same kind, but smaller, 
towards the anus. The last segment of the body has underneath an oval 
fin (nageoire) in the form of a leaf, and the anus is furnished with two 
fleshy horns. The nympha is furnished with two little horns on the 
head and two elliptical nageoires at the anus. It remains in this state 
only ten or twelve days. ‘To this may be added that the viscera appear 
to consist of a simple alimentary canal, largest in the centre of the body 
where the food remains during digestion. The body of the animal con- 
sists of innumerable crystalline fibres, woven together like net work. 
It is more rigid than its appearance seems to indicate, and it retains this 
rigidity to a remarkable degree after death. 
Accident made me acquainted, a few years since, with the fact that 
these little animals devour, with astonishing rapacity, the Water Flea 
(Monoculus Pulex, Linn., Daphnia Pulex, Miller) and that they are 
an instrument, in the hand of Providence, for preventing their excessive 
* Corethra culiciformis, De Geer, VI. 372. t. XXIII. f.4—12. Cor. plumi- 
cornis, Reaumur, Vol. V. 40, Tab. VI. f.4—15. Tipula chrystallina, De Geer, 
149.202 Itis doubtful whether it be De Geer’s insect: the respiratory horn 
is wanting in our species. Cor. plumicornis, Meigen, Dipt. Eur. Vol. I. 15. 1. 
Corethra lateralis, Latr, and Panz, 
