Note n — BOOK IV.
Reading edition
The Insects that for the most part discolour the Waters, are the small Insects of the Shrimp-kind, called by Swammerdam, Pulex aquaticus arborescens. These I have often seen so numerous in stagnating Waters in the Summer-Months, that they have changed the Colour of the Waters to a pale or deep Red, sometimes a Yellow, according to the Colour they were of. Of this Swammerdam hath a pretty Story told him by Dr. Florence Schuyl, viz. Se aliquando Studiis intentum, magno quodam & horrifico rumore fuisse turbatum, & simul ad causam ejus inquirendam excitatum; verùm se vix eum in finem surrexisse, cùm Ancilla ejus pœne exanimis adcurreret, & multo cum singultu referret, omnem Lugduni [Batavorum] aquam esse mutatam in sanguinem. The Cause of which, upon Examination he found to be only from the numerous Swarms of those Pulices. V. Swamm. Hist. Insect. p. 70.
The Cause of this great Concourse, and Appearance of those little Insects, I have frequently observed to be to perform their Coït; which is commonly about the latter end of May, and in June. At that Time they are very venereous, frisking and catching at one another; and many of them conjoined Tail to Tail, with their Bellies inclined one towards another.
At this Time also they change their Skin or Slough; which I conceive their rubbing against one another mightily promoteth. And what if at this Time they change their Quarters? Vid. Book VIII. Chap. 4. Note (f).
These small Insects, as they are very numerous, so are Food to many Water-Animals. I have seen not only Ducks shovel them up as they swim along the Waters, but divers Insects also devour them, particularly some of the middle-sized Squillæ aquaticæ, which are very voracious Insects.