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The SB2Oj0%7#% of MN AD UW RE Sox, 
A catalogue of the infetts referred to the fourth order or cla/s of natural changes, 
which we call the Vermiform Nymph. 
Fi TER having fet forth, with all the per- 
{picuity and diftin¢tion I have been able, 
the four orders of changes which I have efta- 
blifthed, and before enumerated the infects of - 
the fecond and third order, I now proceed to 
recount thofe creatures which I obferve to be~ 
long to the fourth. A great number of thefe 
Thave preferved in my Mufeum. 
Firft, Irefer to this fourth order the eggs of 
infects in general: not only thofe, which pro- 
duce a perfect creature according to the firft 
order, and thofe which, in the fecond order, 
contain a Worm; but alfo thofe which, in the 
third and fourth orders, produce a Worm or 
Caterpillar. For I obferve, that all thefe crea- 
tures and the Worms are difpofed in their eggs 
and skins, nearly in the fame manner as I have 
faid the Nymph of the fourth order, a littke 
before defcribed, is in its uncaft skin. Even 
thofe little creatures, which iffue perfect or im- 
perfect out of their eggs or fhells, caft two 
skins at the fame time: and this has appeared 
to me very evidently in fome; nay, I can fepa- 
rate even the external from the internal in 
fome of them, as I fhall thew hereafter in my 
figures. From this the reafon is evident, why 
I fay that thefe infects lie in their eggs like 
Nymphs, and are as much removed from our 
view as the Nymphs cf our fourth order, juft 
now defcribed; that is, as I have already ob- 
ferved, the external skin, in each cafe, prevents 
the Nymph from being feen and known. 
Of thofe eggs, which, in my firft order or 
clafs of changes, I called Oviform-Nymph- 
Animals, and, in the fecond, third, and fourth 
orders, Oviform-Nymph Vermicles ; I preferve 
a great many fpecies, vaitly different from each 
other, not only in fhape, fize, and colour, but 
in their origin likewife, being, as I have al- 
ready obferved, the produce of different infects. 
Particularly, there are in my collection fome 
very minute Flies, immediately {prung from 
the eggs, which the Moths faften with a kind 
of glue round the branches of trees, in form of 
aring. Hence it plainly appears, that the eggs 
of fuch infeéts belong to the firft mode or me- 
thod of the fourth order. 
Having faid thus much of eggs in general, I 
now, in the fecond place, and in a more parti- 
cular manner, refer the Worms found in our 
privies, or neceflary-houfes, to the fame order, 
and the fame mode of change, as, on their 
alteration to Wermiform-Nymphs, they lofe 
nothing of their original fhape ; but are only 
covered with a hard and ftubborn skin. I can 
produce that fpecies of thofe Worms, and of 
their Vermiform-Nymphs, from which the 
common Flies of neceflary-houfes proceed ; 
future experiments. 
and have therefore given, in the XXXVIIIth 
Table, drawings of this infect in the Worm, 
Nymph, and Fly-{tate, befides one of its eggs, 
which are very remarkable, drawn from a {pe= 
cimen I keep among{t my other curiofities of 
this kind. 
Thirdly, I place in this order the Vermiform- 
Nymph of the Gadfly, as it perfectly retains 
the form it wore in the Worm-ftate. The 
XXXIXth, XLth, XLIft, and XLIId Tables, 
with their explanations, give a fatisfactory ac- 
count of every thing for which this infec is 
particularly remarkable, in difpofition, fhape, 
and changes from a Worm toa Fly; including 
the figures of the apparent Nymph, and that 
of the real Nymph, which the apparent 
Nymph includes. ‘This Fly, as Ariftotle rightly 
obferves, proceeds from a kind of broad and 
flat water Worm; the fame with thofe infeéts 
which Aldrovandus, ‘without knowing that 
they produced the Gadfly, has defcribed by the 
name of Water-worms, or Inteftines. I pre- 
ferve four fpecies of this Worm, with the Flies 
to which they change; as likewife an apparent 
Vermiform, or worm-like Nymph, of a very 
fingular fhape, and the real Nymph, extracted 
by diffection from the infect in that motionlefs 
condition. I have frequently met with this 
kind of Fly, about the end of fummer, in the 
flowers of the garden-par{nep ; though, at the 
time when I formerly made my felect obferva- 
tions, I could not difcover what their food was. 
‘I likewife reckon of this order the Vermi- 
form, or worm-like Nymph of the Tabanus, 
or Breezefly ; though I am, as yet, at a lofs for 
its * origin: but I have great reafon to believe, 
that the manner of its becoming a Fly is the 
fame with that of the Afilus, or Gadfly. It is 
very remarkable, that nature has given thefe 
infects an aculeus, or fting, as well as a trunk; 
fo that they may either make ufe of the trunk 
to procure the honey, dew, and other juices 
which fpontaneoufly offer themfelves upon 
plants and flowers; or of the aculeus, or fting, 
to fuck blood of fuch creatures as they are 
obliged to kill or wound to feed upon. How 
admirable the mercy of their Great Parent, in 
having fupplied them with this double refource 
in their neceflities! Gnats feem to partake alfo 
of this advantage; but as to other infects, 
which feed upon blood, fuch as Bugs and Fleas, 
I muft refer, for the fhifts they can make, to 
Another thing remark- 
able in thefe infects is, that the honey-juices- 
they fuck up with the probofcis, or trunk, are 
always accompanied by a quantity of air, 
which may be very eafily feen, efpecially in 
the trunk of the Butterfly. 
* The origin of this Fly is, indeed, very flrange. The parent lays its egg in the fundament of a horfe, watching the opportu- 
nity of the eeattee’s Poidine its avatione far this purpofe. . From this egg are produced the Worms which farriers call Bots, in the 
inteftines of horfes. Having lived their time in the creature, they are voided with its dung, and take theiy chance for pafling the 
Nymph-ftate upon or juft under the furface of the ground; after which they appear Flies, like the parent. 
In 
