DAY 
evening; and, before the fun rifes next morning, 
it is no more. Five hours generally compleat it's 
contracted fpan of life ; during which, if it is for- 
tunate enough to efcape the filhes, the dragon-flies, 
and the reed-fparrows, it depofits it's impregnated 
eggs in the waters, and dies before the midnight 
cold. The worm, however, which is hatched from 
the egg of this fly, lives and feeds at eafe in the 
waters, enioying a much longer exiflience, and that 
in more fecurity; for it covers it's tender frame 
with a motley cafe of it's own conftrufting; and 
lives, unfufpeded and unfeen, for one, and fome- 
times nearly two years. 
The Day-Fly has an oblong mouth; it is defl:i- 
tute both of teeth and feelers ; there are two large 
ftuds on the head, exaftly above the eyes ; the 
wings, which are carried (landing upwards, are 
unequal in fize; and the tail has briftles projefting 
from it. 
Day-Fly, White-Winged. Infecls of this 
fpecies fly with great velocity: they abound near 
running waters during the months of June and 
July, Supplying multitudes of fifhes with food, 
which eagerly watch them v.'hile depofiting their 
eggs; and no fooner do they propagate their kind, 
than they pay their ranfom with their lives. The 
antlers of the Day-Fly have a multitude of knotted 
joints, which grow fmaller towards their points; 
the brift:les of the tail are hard and firm; the head 
is of a dun<;y brown colour; the eyes are green; 
the fl;uds above the eyes are a jetty black and lu- 
cid; the mouth forms a kind of amber- coloured 
beak; the trunk is a tawny brown, with a brighter 
fpot in the centre; the body is a dull brown with 
pale rings; the legs are a greyifh or afh-colour; 
the tail is a pale brown ; and the brift:les are ruddy. 
Day-F'ly, Rock. For the hiftory of this fly, 
which is particularly curious, we are indebted to 
the late ingenious Dr. Hill, who informs us, that 
he became acquainted with this little infc6l in the 
following very Angular manner. Having ob- 
fcrved fcveral oblong, greyifh tubes or cafes, run- 
ning in various direftions on a flione obelifk 
creeled before a certain houfe in London, he was 
inclined to fuppofe that they were tubuli, or cafes 
of fea-worms, petrified; but finding that this obe- 
iiflv carried evident marks of the chiflTel, and that 
the little tubules were wrought over them, he di- 
redled fome to be picked off, but found them as 
hard as the reft of the ftone, and affixed to it with 
great folidity. However, by the afliftance of a 
hammer, a few of them were difengaged ; but they 
exhibited nothing fiielly in them, being mere ftony 
tubes, formed of the fubftance of the obelifk in 
fmall granules cemented clofe. 
Thus, as theDoftor informs us, the matter refted 
for fome time ; but his curiofity being awakened 
by the fingularity of the incident, he examined 
large mafles of ftone wherever they prefented them.- 
felves ; and, happening to pafs into Buckingham- 
jfhire in the month of July, he there found means 
to unravel the v/hole myftery. 
Several large ftones, partly immerfed in water, 
were, in thofe parts of them which remained dry, 
covered with grey ftony tubules, of the fame kind 
as he had formerly obferved on the obelifk ; and, 
in the fpace of one evening, he difcovered more 
than fifty flies about one mafs, v/hlch evidently 
owed their origin to the womis enclofed in the 
tubules. Thefe flic-s are very beautiful creatures, 
and fomewhat refernble the phryganea in tiie fliort- 
jiefs of their duration^ as well^ as in various qther 
D E C 
particulal's. The Do6lor obferved the ^males bu'- 
fied in depofiting their eggs in all the vifible cracks 
and crevices of the ftones, where the worms form 
tubules for themfeives, and probably live in that 
ftate for one, or even two years. 
The head of this fly is lioary, and of a fine green 
colour, with a black round fpot on it's centre fliin- 
ing at the top; the eyes are a deep black; the ftuds 
are brown ; the antlers are long, proje6ling ftraight 
forwards, and ufually croflfed ; the mouth is dufl<y ; 
the trunk, which is a lively green, is united to the 
body by a kind of neck of a gloflTy green ; the back 
is beautifully variegated with ftreaks and dots of 
gold; and the fcutcheon is of a lighter green. The 
body is thick, and green; the legs are a pale brown j 
the wings are a pearly grey, elegantly veined and 
clouded with a pale blue and a light brown; and 
the briftles are of an amber colour. 
DEATH-WATCH. The Englifti name of 
the pediculus, or wood-loufe, a fpecies of termes 
belonging to the order of aptera, and clafs of in- 
fefts, in the Linnsean fyftem. It is nearly of the 
fize of the common loufe; and it appears that the 
ticking noife commonly heard, proceeds either 
from the male or female, and is exprefllve of their 
amorous dalliance. This found hath long been 
confidered by weak minds as a prefage of death in 
thofe families where it is heard; and hence this in- 
fe(5l is alfo called pediculus fatidicus, mortifaga, 
and pulfatorius. 
There are two fpecies of Death-Watches ; one 
of which is aptly defcribed by Mr. Allen, in the 
Philofophical TranfaClions. According to this 
gentleman, it is a veiy fmall beetle, five-fixteenths. 
of an inch in length, of a dark fpotted brown co- 
lour, and having pellucid wings under the vaginae,, 
a large cap or helmet on the head, and two antenna 
proceeding from beneath the eyes ; and the part 
with which it beats is the extreme edge of the face,, 
which he calls the upper lip; the mouth being pro- 
trailed by this bony part, and lying underneath en- 
tirely out of fight. 
The above account is confirmed by the cele- 
brated Dr. Derham; with this variation only, that 
inftead of ftriking with the upper-lip, he obfen^ed 
that the animal drew back it's mouth, and beag 
with it's forehead. I'his ingenious naturalift is 
faid to have preferved a male and a female in a 
box for feveral months, and to have induced one 
or other of them to beat, whenever he thought pro- 
per, by a nice imitation of it's noife; and, by this 
ticking found, to have repeatedly excited the m.ale 
to an amorous conne^^lion with the female. 
The fecond fpecies of Death-Watch is an infect 
apparently very difi^erent from the firft. The form- 
er gives only fcven or eight ftrokes at a time, and 
very qu ick ; but the latter often beats for feveral hours 
together without any intermifllon, and it's pulfa- 
tions very much refernble the ticking of a watch. 
This laft', which is a fmall grey infe6l, when viev/ed 
v/ith the nalied eye, appears like a loufe, and ori- 
ginates from a minute white egg confiderably 
fmaller than the nit of that animal. In March, 
the infedl is hatched, and creeps about dragging 
it's fhell after it. ' When it fi-pft quits it's covering, 
it is even finaller than it's egg, though that is 
fcarcely difcernible v/ithout a microfcope. In tliis 
ftate it is fomewhat like the mite found in cheefe ; 
and, from this diminutive condition, it gradually 
attains to maturity. 
DECACTIS. An appellation given by fome 
naturdlifts to a kind of ftar-filh of the branched or 
" aftrophyte 
