From The Select Works of Antony van Leeuwenhoek as translated by Samuel Hoole (1798):
Fig. 16, ABCDEFGHIKLMN, represents an entire Flea, glued by the back to the point of a needle, and so placed before the microscope, but being first killed, because it would be impossible to make a drawing of a Flea while alive. Nor, indeed, did I intend to have given a drawing of the whole Flea, but a certain learned gentleman strongly urged me to it, saying, that the world would thereby be more convinced, that Fleas are not produced from corruption, but in the ordinary way of generation, and I therefore complied with his request. In this animal a great number of blood vessels were to he seen, particularly in the belly, but the limner only drew a few of them, saying, that it was not in his power to imitate the remainder in his drawing.
This Flea appeared to me, through the same microscope, eight times larger than here shewn, though the limner declared that it did not seem any larger to him. Nor could I ever have believed that there was such a diversity in the sight of different people as I now find to be the case. But this limner was very short sighted.
At D E F are shewn the hind feet; F G H the middle feet; and KL the fore feet; placed on the head: and between these lie the organs or weapons with which the Flea pierces or bites, and seeks its food. L M N are two horns on the Flea’s head.
For contrast, view Robert Hooke’s flea as found in Micrographia in this
entry at Evolving Complexity.