Essays on the Microscope / Containing a Practical Description of the Most Improved Microscopes, a General History of Insects, etc., etc.

by George Adams

OF THE GENERATION OF INSECTS.

One of the greatest mysteries in nature is generation, or that power by which the various species of animals, &c. are propagated, enabling one single individual to give birth to thousands, or even millions of individuals like itself; all formed agreeable to proportions which are only known to that ADORABLE WISDOM which has established them. We shall never be able to form any adequate conception of this power, till we are acquainted with the principles of life, and can trace their various gradations in different orders of beings. Many ancient philosophers, from a misconception and perversion of the sentiments of the more ancient sages, imagined that insects were produced from corrupt and putrefied substances; that organized bodies, animated with life, and framed in a most wonderful manner, owed their origin to mere chance! Not so the most ancient sages; they taught that every degree of life must proceed from the fountain and source of all life, and that therefore, when manifested, it must be replete with infinite wonders; but then they also shewed, that if in its descent through the higher orders of being it was perverted, it would be manifested in loathsome forms, and with filthy propensities; and that according to the degree of reception of the Divine Goodness and Truth, or the perversion thereof, new forms of life would be occasionally manifested. The gloom of night still wraps this subject in obscurity; will the dawn of day ere long gild the horizon of the scientific world? or is the time of its breaking forth yet far from us? Be this as it may, insects will be found to conform to that general law of order which runs through the whole of animated nature, namely, that the conjunction of the male and female is necessary for the production of their offspring. Where we cannot ascertain causes, we must be content with facts.

Though insects are, like larger animals, distinguished into male and female, yet in some classes there is a kind of mules, partaking of neither sex, though themselves originating from the conjunction of both: many other particularities relative to the sexes can only be touched upon here. In many insects the male and female are with difficulty distinguished, and in some they differ so widely, that an unskilful person might easily take the male and female of the same insect for different species; as for instance, in the phalæna humuli, piniaria, russula. The dissimilarity is still greater in those insects in which the male has wings and the female none, as in the coccus lampyris, phalæna antiqua, &c. In general the male is smaller than the female. The antennæ of the male are, for the most part, larger than those of the female. In some moths, and other insects which are furnished with feathered antennæ, the feathers of the male fly are large and beautiful, while those of the female are small, and hardly perceptible. Some male beetles are furnished with a horn, which is wanting in the female.

“Pleraque insectorum genitalia sua intra anum habent abscondita, et penes solitarios, sed nonnulla penem habent bifidum: cancri autem et aranei geminos, quemadmodum nonnulla amphibia, et quod mirandum in loco alieno, ut cancer, sub basi caudæ. Araneus mas palpos habet clavatos, qui penes sunt, juxta os utrinque unicum, quæ clavæ sexum nec speciem distinguunt; et fœmina vulvas suas habet in abdomine juxta pectus; heic vero si unquam vere dixeris: res plena timoris amor, si enim procus inauspicato accesserit, fœmina ipsum devorat, quod etiam fit, si non statim se retraxerit. Libellula fœmina genitale suum sub apice gerit caudæ, et mas sub pectore, adeo ut cum mas collum fœmina forcipe caudæ arripit, illa caudam suam pectori ejus adplicet, sicque peculiari ratione connexæ volitent.”

Insects are either oviparous or viviparous; or, in other words, the species is perpetuated either by their laying of eggs, or bringing forth their young alive. The former is the more general case; there are but few instances of the latter. Those insects which pass through the different transformations already described, cannot propagate till they arrive at their imago or perfect state; and we believe there is seldom any conjunction of the sexes in other classes till they have moulted, or put off their last skin, the cancri and monoculi excepted.

To form a just idea of the ovaries of insects, I could wish the reader to consult the description that Swammerdam has given of that of the queen bee, and to take a view of the elegant figure that accompanies it, a figure that speaks to the eyes, and by them to the imagination. Malpighi has given a description of the ovaries of the silk-worm moth.

Reaumur mentions six or seven species of two-winged flies that are viviparous, bringing forth worms, which are afterwards transformed into flies. The womb of one of these is singularly curious; it is formed of a band rolled up in a spiral form, and about two inches and an half in length; so that it is seven or eight times longer than the body of the fly, and composed of worms placed one on the side of the other with wonderful art: they are many thousands in number.[81]

[81] Reaumur Mem. des Insectes, tom. 4, p. 415.