The 4s TO RoW of BNE SRI CUTS. 
Th this order alfo I rank the Horfe fly, par- 
ticularly fo called, of which I have, as I think, 
feveral different {pecies. I cannot indeed pof- 
fitively affirm, thas they all properly belong to 
it; for to do that, I fhould have many more 
obfervations, which I muft leave to be made 
by others that can take due pains, and have 
more liefure. 
Fourthly, I place in this order the Vermi- 
form Nymph of the ftinglefs Bee, or Mufca~ 
ftercorariae, or Dung fly, of Goedaert ; tho’ 
it agrees with the laft mode or method of this 
order ; for its Worm has a much more deli- 
cate skin, than the Worms hitherto’ taken no~ 
tice of as belonging to the former mode; fo 
that its Vermi-form, or Worm-like Nymph, dif- 
fers greatly in fome parts from the form of 
the Worm in which it before appeared. This 
Worm is beft diftinguifhed by the extraordi- 
nary length of its tail. It is produced from 
eggs which the Fly, to which it turns, depo- 
fites alfo in neceflary houfes. Amongft the 
Flies to be feen in fuch places, fpecimens of 
which I preferve in my Mufeum, there is one 
of which J have now been fpeaking, with feet, 
horns, and tail, and likewife its Vermi-form 
Nymph with the fame parts. All thefe lit- 
tle creatures are feparately exhibited in Tab. 
XXXVI. 
Fifthly, I refer to this order the Vermi-form 
nymph of the Acarus, which exhibits, though 
fomewhat obfcurely, the fhape of its Worm ; 
for as its skin is very tender, it contracts itfelf 
fo as to appear externally of an oblong 
round figure like an egg. I can oblige the 
curious with a view of this Worm’s Nymph, 
the skin it cafts, and the Fly it produces; 
and for the prefent, they may amufe them- 
felves with Tab. XLIII. where thefe cu- 
riofities are all reprefented as big as, and alfo 
bigger than the life, and with the feparate de- 
{criptions that I have given of them. One 
thing very remarkable in thefe Flies is, that in 
its act of copulation, the penis of the male re- 
ceives into its cavity the vulva of the female. 
Sixthly, I count of this order the Vermi-form 
Nymph, of a certain greenith Worm without 
legs, that lives upon the leaves of cabbage, and 
of which I intend to give a hiftory in its proper 
place. In the mean time, I prefent the readers 
with figures of the Worm itfelf, its true Nymph, 
and the Fly iffuing from it, in Tab. XLV. Fig. 
xxvi. and following figures, This Worm in 
the Nymph-ftate lofes more of its form than the 
- Acarus, as it has a more delicate fkin; but this 
patticular will hereafter be taken notice of in the 
hiftory of the infec. 
Seventhly, I give in this order, which I have 
eftablithed, all thofe Vermi-form Nymphs, or, as 
fome call them, eggs of Worms, which are no- 
thing but the Worms themfelves contracted into 
the form of an egg, and are very prepofteroufly 
thought to proceed from putrified animal fub- 
ftances. Such Worms, after lofing all motion, 
change to true Nymphs within their external skin, 
and fo refemble Vermiform Nymphs; from which 
in a few days, there proceed a great number of 
different kinds of flies. Nor do thefe flies differ 
only from each other, but likewife the Worms, 
35 
from which they originally, and the Vermi-form 
Nymphs from which they immediately proceed, 
have the fame variations; for fome of thefe 
Nymphs are in appearance more like eggs than 
others, in proportion to the delicacy of the Worm’s 
{kin which produces them, or to the refemblance 
which the Worm itfelf has to an egg. 
Ajl thofe Worms void their excrements on the 
flefh upon which they feed, which not only 
makes fuch flefh putrify, and flink the fooner, | 
but increafes its natural ftench and putrifaction. 
Redi has defcribed many fpecies of thofe Vermi- 
form Nymphs; but he calls them all eggs, with- 
out making the leaft mention of their being the 
real Nymphs of Worms, changed to that ftate, 
without cafting their external {kin. However, we 
muft allow him the honour of having proved, 
by the moft folid arguments, that thefe Nymphs, 
or eggs, as he calls them, are not generated of 
putrifaction. 
Eighthly, Iinnclude, in this fourth order, all 
thefe Worm-like, or, as they are called egg-like 
Nymphs, produced from contracted Worms, 
which we know, by obfervation, conceal them- 
felves in the bodies of living Caterpillars, out of 
which they again eat their way. ‘Thefe Worms 
then lofe all motion without cafting their external 
fins, fo as. toaflume the appearance of Vermi- 
form or Worm-like Nymphs; and, in a few 
days more, they turn to many very different {pe- 
cies of Flies. I muft own it an error, to give 
the epithet of Oviform or egg-fhaped to every 
kind of Nymph produced in this way; for, 
there is, on the contrary, fo great a variety in 
their forms, that it would be the bufinefs of an 
entire treatife, to give feparate defcriptions and 
figures of them all, 
Ido not find that thefe Worms void any ex- 
crements, after quitting the bodies of the Cater- 
pillars upon which they feed; they immediately 
contract themfelves, and become motionlefs within 
their external fkin, till at laft they are thus under 
its coverture changed into true Nymphs, in every 
refpect like thofe already defcribed, as belonging 
to the firft {pecies or method of the third order. 
This kind of mutation in infeéts, performed by 
their contracting themfelves into the Nymph- 
form, after gnawing a paflage out of the bodies 
of Caterpillars, into which they had infinuated 
themfelves, has not as yet, as I know of, been 
obferved by any writer. 
T have alfo remarked, that thefe Worms have 
fometimes remained in the hollow of the Cater- 
pillar’s body, after they had entirely devoured its 
fleth, and thus turned to Flies, after paffing thro’ 
the Nymph-ftate ; fo that, in order to appear, 
they muft have forced a paflage through three 
different fkins, namely the membranaceous fkin 
immediately covering the Nymph, the external 
fkin of the Worm from which they originally 
proceeded ; and laftly, the fkin of the Caterpil- 
lar, whofe carcafs they had preyed upon. 
For want of fufficient experiments in an af- 
fair that would require a great many, I cannot 
as yet take upon me to determine, how the 
Worms, of which I have been {peaking, come 
to be found in the bodies of Caterpillars; whe- 
ther it be that they are introduced into them in 
thie 
