The transformation of Insects

Insects to the popular mind are not we fear very interesting creatures: if any interest be shown in them, it is as to the best means of compassing their destruction, for they are too often regarded as useless pests to be ruthlessly destroyed at every opportunity. Science however by the aid of the microscope & the patient investigations of the naturalist has revealed to us in the insect world forms of beauty, exquisite colourings, wondrous structures even skill & instinct scarcely to be surpassed by animals of higher organisations while it is also seen that they fill no unimportant part in the economy of nature. The Natural world presents to us many strange phenomena but none more wonderful than the metamorphoses of insects. However rudimentary our knowledge of the habitats of insects we know that they undergo certain changes and have several distinct sates & stages of existence. And yet it is related by Darwin that as recently as 50 years ago a certain M. Kenous was arrested on a charge of witchcraft by the civil & ecclesiastical authorities of St. Fernands in Chile because he actually kept some caterpillars that turned into butterflies. It is now universally known however that insects quit the egg in a very different form that they ultimately assume passing in fact through four different states – the egg, the larvae, the pupa & the imago or perfect insect. Immediately on their exclusions from the egg thy are soft, without wings & usually somewhat like worms. The coloured & often hairy larvae of moths & butterflies are called caterpillars & the white & more compact larvae of flies & many beetles are called grubs & maggots. During this period of their life, in which they are voraciously & cast their skins several times, insects live a shorter or longer periods; some only a few days or weeks, others several months or years. They then cease eating, fix themselves in a secure place, their skin separates once more & discloses an oblong body & they have reached the third state of their existence. From the swathed appearance of most insects at this stage it is called the pupa state; of these the less known forms are covered with a membranous skin enclosed in separate & distinct sheaths, the external organs, as the antennae, legs and wings of which are consequently not closely applied to the body but have their forms for the most part clearly distinguishable. As these pupae are often tinged with yellow, they were called by the Greeks Chrysalides, a term we now universally employ. In this pupa state the insect is dormant usually mobiless & eats no food. But this is by no means universal, in many cases the changes are not so complete or clearly defined, the pupa, in place of taking no food & differing altogether in form from the perfect insect, continues to eat & lead an active life & differs very slightly in form from the perfect insect. Such, for instance, is the case with the spider, the cricket & the grasshopper in which the changes are so slight as to cause many to doubt whether they undergo metamorphosis at all. As however these insects cast their skin on certain periods & undergo changes though slight in their external & internal conformations they are still regarded as subject to metamorphosis. Another type of active pupa is found in those that are aquatic in the earlier stages of their existence. They not only differ widely in form & structure but embrace in themselves different species & inhabiting different worlds. At one period they live in water & could only exist in that element, in another the air is their home & their former condition would be equally fatal to them, for they are fitted for their different abodes by new organs & instruments & a new form in each. This type finds an illustration in the common gnat. The apparent suddenness of the changes affected by metamorphosis has astonished & puzzled many, but they are not so sudden as at first sight appears. The caterpillars curl up & becomes a chrysalis, the chrysalis bursts & discloses a butterfly, but this is merely the throwing off of the outer skin. The draining aside of a curtain & the revelation of a form that has been in preparation for days, sometimes for months. Trammerdam held that the larva contained within itself the germ of the future butterfly enclosed in what will be the case of the pupa which is in itself included in three or more skins one over the other that will successively cover the larva. Thus he says the caterpillar should be called not a simple but a compound animal and that one should rather term their changes developments & not transformations, This is pronounced by Sir John Lubbock to be a mistake but he admits that if you examine a larva just before it is full grown you may discover the future pupa & if you examine a pupa about to disclose a butterfly you will find the future insect, soft indeed but easily recognisable lying loosely within the pupa skin. These interesting facts may be proved by anyone who will plunge a caterpillar about to assume the pupa state into vinegar or spirits of wine & letting it remain there to give consistency to its parts when even a rough dissection will enable the operator to detect the future butterfly.

[9 loose page held together with a pin, were found in the archives. Mr. Styles has labelled them as Mr. Roberts Paper]