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1 2 3
6
AN ECOLOGICAL STUDY OF THE MAYFLY
CHIROTENETES
BY
WILBERT AMIE CLEMENS, M.A.
Introi
Then
The S
The h
SUMMAl
LiTERA
EXPLAI
TABLE OF CONTENTS
PAGE
Introduction -
The Nymph : General habitat, Chemical analyses of the
water, Temperatures, Relation to materials
forming the creek bed. Relation to light. Relation
to current. Food, Relation to the oxygen and
carbon dioxide content of the water. Associates,
Enemies, Severities of stream life. Protection,
Regeneration c
The Subimago: Emergence, Factors effecting the
length of the subimaginal period, Enemies,
Protection , ^
The Imago: Transformation, Flight, Oviposition, Egg,
Enemies, Protection, Length of life .' 38
Summary
40
Literature Cited .^
42
Explanation of Plates »~
AN
N.
have b
our ki
co-opei
small,
tion of
out du
sjx'cies
descrit
Chi rote
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illustra
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Ge
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New \
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accessi
AN ECOLOGICAL STUDY OF THE MAY-FLY
CHIROTENETES
Introduction
Notwithstanding the numerous investigations which
have been made upon the life phases of various Ephemeridae,
our knowledge concerning the physical factors and their
co-operation in relation to individual species is singularly
small. It was for this reason that the writer, on the sugges-
tion of Professor James G. Needham, undertook and carried
out during the years 1913-1915 the detailed study of a single
sjx'cies in a very restricted area, the results of which are
described below. The sjjecies chosen for study was
Chirotenetes albomanicatus Needham, the nymph of which is
common in and characteristic of the riffles and rapids of the
streams of the Cayuga basin. The various stages of the
insect are described by Needham ('05). The description is
illustrated by two plates and is accompanied by some data
on the habits of the nymph and subimago and the food of the
nymph, Morgan ('11) gives some brief observations made
on this species in Fall Creek, and again ('13) gives further
biological data with illustrations of gills and egg.
The writer is greatly indebted to Professor Needham for
invaluable advice and for many helpful suggestions freely
given during the course of the investigation.
The Nymph
General Habitat. — The nymph of Chirotenetes albomani-
catus inhabits all the larger streams in the vicinity of Ithaca,
New York, but this study has been mainly confined to one
stream, Cascadilla Creek. (Contour map. Fig. i.) It was
chosen chiefly because its smaller size made it much more
accessible for observation and experimental work. The
6 Clemens: Ecological Study of Ciiirotenetes
creek has an approximate length of eight mile. It .n 1
m an up and alder suimr. o„^ a . 'K'"^ miies. it arises
emptyin^g into cly'/a Lie" iZ' 'Vh"'''"'^ "^''''''4
divided into three reSonsm.n if '"'''?'" •"^>' ^\
mately six miles inTn/th ^i, "'^"'' '''""*'''" ^PP*-*™-
Lake by the Iril^^TretTM t '"''"' I!' ^'"'"'' I
wind, among the ald7rs fl^wTn, ovLTm^L'^I V"™
vegetable d^hHa or>^ *i, '^^'^'"s ^.^^"^ a bed of dark brown
shrub, and Ster^ t^f 'th^"; "' bank' '"rderc,! with
bottom Aft.rT. ""O .™bble and occasionally on the reck
takeH'stfalSt n3h ^T *^''^"^'' ^""'y '"e stream
pieces of rock orrnr ^t thT? r . ! ^ ^^^^^^ ^^^^*^^ ''^"^
in succession smXr. ^^"^f^ '^^ ^^^' ^"^ ^^en foll.nv
For the lar^^o v" [ ?•'' ''"^ '^'^^''^' ^''^'■^^' ^and, silt.
and Scots ieep and ^ luSiSr ''' ^^r ^^"^^^^ ""^
the water from the lake ^xt^'r^ "^^ ^^^^'"^ "P °f
abundant at tl^e base nf'th vn"PP^' °^ CAzVo^ene/e. are
_ at the base of the hill but gradually decrease in
sto„elsX:;;:ish;^ir:"' £ tr^^r '^^ ^■^^"'^"^^ °f ^'•^•^ -^ --e.
spherical form. ' ''""'' ^"'^ ™""'^^'' ^^ges tending toward a
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Clemens: Ecological Study of Ciiirotesetes 9
numlxTs toward the mouth, disappearing when the slack
water is reached.
Chemical Analyses oj the Water. ~\n order to obtain
dihnite knowledge concerning the medium in which the
nymphs live, chemical analyses were made at various times
fn.rn December i, 1914, to August 10, 1915. The results are
given m tabular form. Comparison with analyses of the
w.iter of the neighbouring Fall Creek shows a \ery close
correspondence. Theamount of pollution is not excessive asin-
(liiated by the nitrogen » jTMu na. hch. hph. _ _
Fig. 2.— Relation of the oxygen content to temperatures of Cascadilia Creek
- oxygen in parte per million at 760 mm. p euure.
•■-■-- = temperature.
niTf MO.
doubtless as a result of the turbulent nature of the creek.
I"igure 5 shows the amounts of oxygen present reduced to
760 mm. pressure as compared with the amounts of saturation
at the same temperatures and pressures. The carbon dioxide
content is low, probably for the same reason that the oxvcen
content is high.
Temperatures.— KtcoTd.?, of the temperatures of the water
in eascadilla Creek were taken almost daily for over a year
tor the purpose of obtaining information regarding the
fluctuation in temperature from day to day, the maximum
10
Clemens: Ecological Study of Chirotenetes
r^iT Jl'^P^'^^T' ^^^ '^"«*^ °f ^^^ ^ero period, and the
relation between the temperature and the oxygen cont nt
n a swiftly flowing stream. The records show that the wate
emperature fluctuates with the air temperatui^ but nev '
rLn h1 H ' • *''T? °^ *^" '^"^'■- Tne highest temperatu
recorded during this period was 28»C. on June ^, igu
The maximum air temperature on this day. as recorded by the
Weather Bureau branch of the United States Department o
day before 32.2 C. The temperature remained at 0° C
from November 8, 1914, to March 28, 1915. except for a rise
to 3 L. during four days in February, 191 5. The relation of
the oxygen content during the yearVo the femperat,^ f ^"h
water is shown in Fig. 2.
i?e/a/zon to Materials Forming the Creek Bed.—¥k\A
observations show that the nymphs of Chirotenetes occur in
greatest numbers m those parts of the stream where there are
deposits of rubble and stones in moderate to swift current
They occur most abundantly in tiie upland portion of the
creek and so numerous at times are they in places that as
many as sixteen nymphs of various sizes have been found
f n n\t "^''"^ °^ ^ "" 4 m^^^^' ^^'^'^ ^«"Jd mean a nymph
to each three-quarters of a square inch. Forty nymphs have
been found beneath a piece of rock about one foot squa;e
Frequently a flat shelving piece of rock may be lifted sightly
and the nymphs observed clinging to the under surface in
S.T"^- ^'ll^^^^hor may-fly nymphs such as Epearus,
^!f,^^ fn ,f ^^'■"^ ^"d B^^'i^' stonefly nymphs, caddis
worms and the water-penny. Needham ('05) reports some
observations which he made in Fall Creek goi^e.^ '' I hav
creek bed is flat shelving rock over which the water streams
1?,^.^, •" I" .such places the flat, rocky floor of the
stream is covered with a thin filmy growth of algae, with
tT^T "!!f °^ '^ u^^f^ seine-maker, Hydropsyche; and
mL. f^K. S' i ^^^ ^°°'" '^«^^ ^'■^ fringed Jith black
masses of blackfly larvae, Simulium. Simulium and Hydro-
Clemens: Ecological Study of Chirotenetes ii
psyche are fixed in their places, but ChiroteneUs wanders about
freely over the ledges, clinging securely even in the swiftest
water, keeping of necessity head up stream, moving by short
quick dashes effected by sharp strokes of its powerful taU
fin and gill covers, moved synchronously. It is found in the
stiller pools at the sides of the current, in which dwell other
may-flies of the genera Caenis and Baetis; and also among the
rocks in the current under which cling other nymphs of
Heptagema, Blasturus and Choroterpes "
Field observations appeared to indicate that th^ lower
sides of s ones and rubble contribute the preferred hahkTJl
Chrotenetes In order to test the matter, however, certahi
ZTr.K """'" ^r^- ^^'"^ ^^'•^ based on the assum^
Snot su t'th"''"'?^ ^'"'^ ".^^ '■^"^^•" '" ^ ^'tuation whic'i
did not suit them if a more suitable situation were available.
A wooden trough three feet long, one foot wide and ten inches
deep was constructed and provided with wire netting at both
ends, so as to allow water to flow through freely but prevent-
ing anything in the trough from escapin'g. In'^he upper end
of the trough was put a flat stone a foot square. The small
crevices between the stone and the sides o^f the trough were
le^tll^o^hP f' T""'- ^^^'"^ *^^ ^*«"^ f-*- the remaining
length of the trough course gravel was placed for a depth just
rih th '^•'''"f'' ^^ '^^ ^^°"^- I" the middle^f \he
Ttrt ^^^ P'f "^u^ P"^ °f ^I'ble each piece about
3>^ inches square. At the lower end was put a pile of small
stones each stone about i^ inches in diameter Tust
enough space was left between these groups of materials to
allow a wire screen to be pushed down between them. The
trough was then placed in the stream and arranged so that
there was a current through the trough of i to 2 3. fe^t
EJ-enrvT^ "r"'^'"^ '° '^' ^^P*^ °'the water. "Thl
twenty-four almost mature Chirotenetes nymphs were put in
ioursT '^' ^""^'^ ^"l^- ^' '^^ ^"d «f twenty-foir
hours the screens were carefully put in position between the
groups of materials, the trough taken f^m the stream the
count'^ Tf^ '■''""^f^ ^"^ '^' "y"^Ph« in each section
counted. Nineteen were found among the small stones, four
12 Clemens: Ecological Study of Chirotenetes
in the rubble, and none on the rock. A series of such experi-
ments was tned; the arrangement and results of a tvoical
set are given as follows:
I
I7.4^c
2
4-8 ^i
95-2 9'c
3
Rock
0
Rock
0
Rubble
5
Rubble
4
Stones
I
Stones
12
Stones
19
Rubble
20
Rock
o
29 -4^0
"0.6',
23 re
77 Sc
5
6
Stones
o
looSt
Rubble
o
Rock
0
Rock
0
Rubble
i6
Stones
15
In all cases the nymphs were put into the trough at the lower
end In conducting the fifth test a blocking of the screen
at the lower end of the trough one day caused an almost
complete cessation of current, and when the trough was
examined it was found that all the nymphs except one had
migrated to the upper end, close to the screen where there was
a slight movement of water. This appeared to indicate that
current was a more important factor than material in the
selection of a habitat. The results of these experiments
mdicate that the nymphs have a decided aversion to open
rock and a slight preference for rubble as against small stones.
Intake
Upper
Clemens: Ecological Study of Chirotenetes 13
Relation to Light.-lt was thought that light might be an
important factor in the choice of habitat. Wodsedalek (' 1 1)
has shown by experiments that the nymphs of Heptagenia
mterpunctata Say are to a strong degree negatively photo-
tactic An experiment was devised to determine the reactions
d Chtrotenetes nymphs to light. A trough 5lX4X3'/8
mches, with wire screens at the ends, was divided into thr^
equal compartments by means of cross pieces reaching from
the upper edge to within an inch of the bottom. A similar
cross piece was put at the lower end against
the screen. At the upper end was a small
intake area where the water entered before
Howmg into the three remaining compart-
ments. The trough was then put out in the
stream under a small ledge where a current of
water could easily be sent through the trough
and where conditions of light were normal.
1 he amount of water was then regulated so
that the surface just reached the lower edges
of the partitions. The bottom of the trough
was rough, offering a foothold for the nymphs.
Ihirteen Chtrotenetes nymphs were put in the
lower compartment over which a close-fitting
cover was immediately placed. At the end
of two and one-half hours not a single nymph
had left the compartment. Then the cover
m^nfi'rftS ^^^ taken off and placed over the upper com-
t"'?;;;°ht"falor"'"°'"-P^'^'"^''t- immediately the nymphs began
but fmir h.H H-° '^'^'^^V'? ^^^ ^^^"g^- I" ^oxxv minutes all
^vln ^^n ^ disappeared into the upper compartment and
^ven minutes later the remaining four had disappeared also
Not one ventured beyond into the small open'^ntaLe are^.'
After waiting ten minutes the cover was removed and aU
leain «nH tl ^^'^ '*"^? ^^^ '"'^ *^^ ^^^^'^ compartment
agam and the cover replaced. At the end of ten minutes all
^L^^^P^'^^^'^f'" '" ^^'^ P^'^- Then the cover w^
At on'c^th""^ qu'ckly placed over the middle compartmeT
At once the nymphs began to migrate and in two minutes all
Middle
Lower
14 Clemens: Ecological Study of Chirotenetes
except one had disappeared into the darkened chamber the
last one following in forty-five seconds. The trough was Icf
m th,s condition for seventeen hours and at the f d of h
time every nymph except one still remained in the midcl
darkened compartment. When the cover was removTth
nymphs scattered. The cover was placed overX lowe
compartment again and when the trough was examfnej s !
area. These experiments were repeated many times The
tTndetief "^ ^'°" ''"^ ^^^°"^ -^^'-•v P^'otaltic
W.C 7^^ *''°'il^ "f^ '" *^^ experiment for habitat preference
^^«t "f."^ 'k ^^^^""'"^ whether or not the nymphs wo" d
n.main on the bottom of the trough if the empty area To '
^bbLw;^'" "^n^r '" "r"^ -^-^ /eLnes ;;
d^cidtlT- ; u "^"'P^^ appeared to show no verv-
decided PH. ence as between stones and pieces of rock Z
SctoT'ci:!? 'r nr^^ °"'^' on^e wrltone'-an
?nnah 1^.1 ' J u ^^^^^ '"^*'°"* ^"y materials, leaving the
mTght ^"r Th^ '"r^^ "' ' ^"''"^^ *° "^'^^ the nymp
might chng. The empty portion of the trough was closelv
covered and the trough put out in the current with the stont
put into the lower darkened compartment. When the trough
was examined twenty-four hours later, all t^e nyZhs °^^^^^
S; this"area ^ "' "^"'^ ^^''' ^" ^^ "^^^P^^ ^^re still
obseSJn! kTn'^' '"If' °^ "- - ^^P^rinients and field
oDservations it appears that current is the more imoortant
Creek where the water is turbulent, swift, and comSvdy
Clemens: Ecological Study of CmRorENETES 15
shallow, it was necessary to have some instrument for current
measurement which could be used in narrow places andX
measurements at slight differences in vertical and horizontal
?fS n ^!l consultation with Professor E W Ser
P> . . ^fP^"^*"^"^ «f Hydraulics. Cornell Univer^ty a
P|tot tube was suggested and an apparatus as Town' in
Figure 4 was constructed. This consists of two copp^rTubls
24 inches long and %, inch in diameter, fastened toSer and
onnected by mern^^'f tlT^'T- "^^^ ^"PP^^ ^"bes are
nd a quarter fn.h • "S^^*" '"^'"^ '^'^ ^"c'^^^ i" length
ana a quarter mch m diameter to two glass tubes each
twenty-four mches in length and '%, inch in diameter The
glass tubes are connected at the top and may
be opened to the air by means of a stopcock
Ihe glass tubes are attached to a board and
between them is placed a scale. This instru-
ment was rated in the canal of the Hydraulic
Laboratory of Cornell University
With the Pitot tube a large number of
measurements were made in Cascadilla Creek.
1 he hrst measurement taken was in the middle
ot a small stream twenty-two inches wide
and five inches deep flowing in a channel in the
D rock in the gorge. It was found that near the
surface there was a velocity of 1.7 feet per
second, while on the bottom the velocity was
I _ o foot per second. A stone with dimensions
tl^ ^^"i,^2X[0X2K inches was placed in
the middle of the channel. Midway between
the surface of the stone and the surface of the
g water the velocity was 1.9 feet per second.
PiS.u'br%rB2'"" J*'^ ^"'^^ce of the stone the velodty was
Sre'^wtrXiS!:/?. !fj P^"" "^^o"^; three-quarters of an inch
=co'?^^tV,;i.'!"''- ° !f ^'"'' ^^^ «^o"e a"d one inch above the bottom
hnt. uu- J u ''^ ^^^ "° perceptible current ; on the stream
over 0.5 foot per second. A measurement in swifter water
16 Clemens: Ecological Study of Chirotenetes
showed a velocity near the surface of 4.3 feet per second
while on the bottom only 2.1 feet per second. Many
measurements were taken round stones in the creek, particu-
larly round shelving stones, and a few results are here given
At a velocity 1.6 to 2.1 feet per second
" b " 2.0 " 2.6 " " "
xC
very low and indications of slight eddy.
u
a
velocity
2
9
feet
per
second
b
II
2
.6
II
ti
tt
a
c
II
?>
.6
II
ti
a
a
d
11
.0
II
ii
<<
•
*
Size of stone = 12X22 inches.
At a velocity i.o to 1.5 foot per second.
" b " 3.0 '♦ 3.5 " "
" c " 2.0 " "
" d " 2.1 " "
" e " 2.3 " "
II
II
Clemens: Ecological Study of Chirotenetes
At f velocity 2.8 foot per second.
17
" h
" i
" i
" k
2.9
3-7
4.6
i.o
too small to be measured with the Pitot
tube.
^n a channel 7K inches deep and three feet wide, the bottom
kvlocity was 1.5 feet per second; close to the surface the
biocity was 2.5 feet per second. A stone almost cubical
Bn form was put in this channel.
At a on top of stone velocity 2 .9 ft. per second.
b behind stone on bottom velocity 0.5 ft. per second.
C behind stone 2^ inches above bottom velocity .0 ft.
per second.
" d at side of stone velocity 2 . 8 to 3 . i ft. per second.
At a velocity 2.9 ft. per second.
]| ** '' 30 to 3.4 ft. per second.
c " 1.5 ft. per second to a reverse of 2.0 fecc
per second.
There was a strong eddy behind this stone at times and
the direction could be determined by turning the copper tubes.
Numerous measurements taken round stones and rubble
in the rapids and riffles of the stream have shown that nearly
111 are so placed that a current of greater or less velocity
18 Clemens: Ecological Study of Chirotenetes
flows beneath them It is in this diminished current under 1
Hve mL?"? fh"' r'''^ ;'r. '''' "^'^p'^^ °f ^*-^' ;
live. Many of the large shelving pieces of rock h-,^,
cuj^nt unde^eath at one point a'nd'no curl^at a'n hel
point. The distnbution of seine-making caddis wcrm
nretn"'''' 1'^°"' t'' ^ ^'^ ^^^ indicatfon as toTd
presence or absence of a current.
Aleasurements were taken on July i, lois over tl,
smooth flat rock in the gorge where the wate sprltds ou i H
broad sheet and where blackfly larvae and seine-makin
:?e tXr "^" ""^ ^'""'^"^- ^^° -^^ m:rurTmt:!|
PTater TAree /n«A« Deep
bZ:"^-'-'- : : ^..f«.t per second.
Close to surface - - 3-4 foot per second.
Midway to bottom - - 30 " "
Bottom — — — _ 2 o " '< "
At various times of high water in the creek mpa«.,«
ments of the vertical distributions of velocitierwerTtakeT
The results of three measurements are a. fnll».,.c. '"
Clemens: Ecological Study of Chirotenetes 19
On July 13, 1915, the smooth rock of the floor of the
itream m the gorge was covered with a thin film of diatoma-
:eous ooze, of Navtcula and Synedra chiefly, just enough to
nake the rocks very slippery under foot. The water over the
jck had a depth of one to two inches. The Pitot tube was
ilact-d mi the bottom in the centre of an area of diatomaceous
Lu'"' . J""^^""'}^ "^'^^ ^-^ ^^^^ P^*" second. The ooze was
ihen cleaned oflf the rock over a large area and the tube placed
exactly the same position as for the first measurement and a
elocity of 2.3 feet per second was obtained. There was thus
decrease m velocity of 13 per cent, due to the ooze. Numer-
ous other measurements showed an equal or slightly smaller
lecrease. On rocks with a fine coating of algal growth and
, measurements showed losses of as much as thirty per
Experiments were then conducted to determine in how
swift a current the nymph of Chirotenetes could maintain itself
A wooden trough fifty-one inches long, four inches wide, and
three and one-eighth inches deep was placed at the edge of a
small watenall so that water would flow through the trough
at a depth of about two inches and arranged so that by raising
orlovv-enng the lower end the velocity of the water could be
vaned. The bottom of the trough was a rough unplaned
board which supplied the nymphs with a foothold. Three
almost mature Chirotenetes nymphs averaging 12 mm in
ength were put in the trough about a third of the distance
rem the lower end where the velocity on the bottom was i 4
feet per second. The velocity was gradually increased until
all the nymphs let go their hold and the velocity of the water
then measured. The greatest velocity which these nymphs
could withstand was one where the velocity on the bottom of
the trough was 4.3 feet per second. With three nymphs
'?J° ^uT' •" '^"Sth it was found that these could maintain
their hold until a velocity of 4.8 feet per second was reached.
A senes of experiments was then carried out in order to
observe the actions of the nymphs of Chirotenetes more closely
m currents of various velocities and to compare their actions
with those of the larvae and nymphs of other insects inhabit-
20
Clkmens: EcoLociicAL Study of Ciiirotenetes
tlut the n-sults nught n„t Inj vitiated by fatigue ' '
Exp. . Iiou,,mv..|,,ci,y 4e„ .Sfci-tpcTsc-cond.
Ull bottom - I o " I 2 " " "
Bottom velocity .9 to 1 .0 feet per second.
'-'It lH)ttom 1 .2 " I ^ " .. ..
auo,e,„:es nymphs able to crawl but carrtj
In™ rc„t"ho,d.'' "^ ™'^™' ^•''- "«--l
off,rtor°"*^i:^^?j.i'-'»^--°?<'-
Chrolcneles nymphs still able to crawl rapidlv
Chtrotenetes nymphs able to crawl slowly
offrtonr'%^:i'"^'^'-r--^-
Chtrotenetes nymphs able to crawl slowly
Epeorus and Heptagenia may-fly nymphs a
hhlTT^' ^ '^''^^ ''«"^-«y nymph ami a
black-fly larva were all able to maintain their
Exp. 2.
Exp. 3.
Exp. 4.
Exp. 5
Exp. 6.
Clemens: Ecological Study of Ciiirotesetes
21
hold and move about. 1 he large stone-fly
walked up against the current with apparent
ease.
Exp. 7. Bottom velocity 5.5 to 5 7 ffi't iht second.
iMay-fly nymphs {Epeortis, Ileptagenia and
Chirotenetes), a small stone-fly nymph, a
water-penny, a seine-making caddis worm, a
black-fly Iar\ a and a fish-fly lar\a iChauliodes)
were put in the trough and the velocity
gradually increased until the stated amount
obtained. The stone-fly nymph walked up
against the current with apparent ease;
Ep€orusc\ung^c\STc\y but remained quiet; the
black-fly larva maintained its hold but curled
up and lay flat on bottom; the water-penny
moved slowly backward; all the others lost
their holds before this velocity was reached
and did so in this onlcr— Chirotenetes, Hepta-
genia, fish-fly larva, caddis worm.
The results of these experiments show that the nymphs of
Chirotenetes chnging to the under surface of stones escape the
main force of the current. The water in such places is moving
very much less rapidly than nearer the surface, but it still
bnngs constant and fresh supplies of food and oxygen to the
nymph which may wander about in comparative security
from many of the dangers which necessarily accompany life
in swift water. When the nymph wanders out on the flat rock
bfd of the stream, it still is in a much rcxiuced current,
especially where the rock is covered with diatomaceous
ooze or other algal growths. The results also show that the
nymph is able to live in rather swift water but that it is
scarcely so well equipped for a swift-water habitat as some
of Its associates with limpet-like forms of body. Neverthe-
less the nymph of Chirotenetes does possess a form of body
adapted to life in flowing water. The hard smooth chitinous
covering reduces the friction of the water particles to a
minimum. The head is well rounded. The thorax gradually
widens and is followed by a depressed abdomen which
" Clemens: Ecological Study of CiiiRorENETEs
condition tends toward a limpet or Heptagenine form l> I
Wowmg experiments were devised to deteLine th^'med.
.cal or adaptive value of the Chuotenetes form fori! .
running water. A mass of grafting wax wei^hi^cr ,s .
was moulded into the shapc'of a con^. the bat "f whtri
5,7 cm. in diameter and the perpendicular 8.25 cm A nJ
wire was put through the cone from the apex toThe an
of the base. This wire was fastened to a small metal 1
the middle of the cone to prevent it from pulRnrout I
cone was attached to a 50-gram spring balance by means -\
fine wire 33 cm. in length. When plaLl in a current of .•
fee per second the cone sank alx^ut 3 cm. below the sur a
28 .ram! Th"lT"'' '^"^ ^""' "P^^'"*^^'" exerted a M
Close to the surface of the water as jiossible. There wa
Tattut of the "''"" '" ^'^' ?T""^ ^^ P"" - ^he b^ia
^me Stilt Ltr"''''"r''f^ '^^ ^"'■'■^"^ ^"d probabh
some extent to the imperfect form of the cone. However iti
certanoln^'' ^'^^ "•^"''"'' "' '^' ''^'^"^ remains :;
certain point f(,r a greater part of the time and also that thi
point was approximately the average of the Wghest I
ram Z"*^ [r'"' !:'. the indicat'or. With thfa; /
d for^of fil f1!"'- ^'1^ ^'^-^ ^^« then moulded inJ
S /rams ^A f "^ the sunfish type and the pull exerted .a.
wihT% "" °^ *^^ ^""""t tyP^ »^^^ a pull of 6 gramJ
rmodelofr^r/"'?'",^"^ ^° ^'■^'"^ ^"th tail up st'ream.
A niodel of a Chtrotenetes nymph gave a pull of 9 grams ^vith
head up stream and 16 grams with head dou^i stream. In
these experiments the total amount of wax was used
of ful ^'^^ *^^* ^^"^ '"■"'' °f ^^^^ fashioned at ihe base
of the cone was of great significance. For example in a
current of i . 2 feet per second a cone with a sharp edge to the
^n^Tf ^ r " °^ 40 grams, whereas with the edges J\
rounded the pull was decreased to 10 grams
Another series of measurements in a current i . 5 feet per
second gave the following results. A cone with a bLe 7 cm.
in diameter with a sharp edge and a perpendicular of 1 1 cm.
Clemens: Ecological Study of Chirotenetes 23
Igave a pull of 50 grams with the base against the current and
a pull of 25 grams with the apex tT the current. A cylinder
8.5 cm. in length and 5 cm. in diameter gave a pull of 18
grams. With one end pointed and directed toward the
current, the pull was 6 grams, while with the blunt end to the
current the pull was 17 grams. With both ends pointed
jformmg a spmdie the pull was 5 grams. A fish m(xlel and
a Chirotenetes model each gave a pull of approximately 6
I grams.
Comparison of the amounts of pull exerted by the
various models is open to the objection that the area of
greatest cross section was not kept constant throughout.
Nevertheless the results demonstrate in a rough mar -or that
the nymph of Chirotenetes possesses a remarkably icient
form of body. This explains in part how it is that C.Aroten-
(tes nymphs are found in association with the flattened limpet-
like forms of the stream.
Food.~May-mes are herbivores. They feed almost
ixclusively upon algae, from the minute diatoms to the
higher filamentous forms. The nymph of Chirotenetes has
(ie\ doped a very remarkable specialization by means of which
It avails Itself of the suspended edible plant material carried
along by the current. The inner sides of the fore femora.
tibiae and tarsi are fringed with long hairs interspersed with
shorter fine ones. These are supplemented by copious short
hairs on the labrum, and on the maxillary palpi and by longer
ones on the labial palpi. When the nymph takes up a
position m the current head up stream, the forelegs are held
out in front of the head and flexed at the tibio-femoral joint
so that the claws are almost contiguous on the surface of the
rock. In this position the hairs of the forelegs and mouth
parts meet and overiap in such a way as to form a straining
apparatus. To demonstrate the use of this strainer a trough
51X4X3^8 inches was placed below an outlet from a tank
and arranged so that a moderate current flowed through the
trough at a depth of one and a half inches. A number of
nymphs which had had no food for twenty-four hours were
put into the trough at the lower end. They soon began to
24 Clemens: Ecological Study of Chirotenetes
rd"otheT?:if'T '^ ^°"°'"' A '"-^"^ of silt. diato„.|
ana other forms of algae was sent down in the current Za\
observations were made by means of a reading ela s T
stramers were soon loaded with the materialTd f?ur nvml 1
were observed to feed upon it. The elongated frLgedS
the maxillary palpi working laterally and the elossae of t
f rmTn^d blV^^r'r ^"^'^ '^^ food mlSsI,
food^:itrfach%frh'e^:;?^^^^^^^^^
and not wanted were expeire^l'bTmovin^g"^ I^g'oTwaSt
allowing the current to wash them away ^ '
To determine what materials were available in tJ,J
ine stream at vanous times throughout the vpar Ti,
..• .u quantitative determinations were made to asrer
w"od'en%reh \°' food available for the nym'pfs' Ira |
such a wav tS,/ '"'5'' ^•'^^ ^^' ^'^^^ »" ^^^ ^^eek in
5Lter?an A !, ""Vfl""^ P;;^^^'^ °^^'' ^^^ ^^^ of a small
of tl • \ "7^"* ^""^^ ^^•■o"^!^ the trough to a depth I
of tv.o inches and at an average rate of 4.0 feet per secon
thra,L7^i ^"^ ^'""^^ '"'""*^"- The catch was filtered
twentfour hn^^' ^^"^- ^'^°hol and allowed to stand fo
twenty-four hours, and the volume then read The catch
STtToriilt ''oTVh' ^°"^'^^''^ proportion of whi^ht^
sistea of Slit. Of this catch it was estimated that at Ipi,r
ceTofTne r ''■Y't l"^'''^ -tterrdlnother^io"
cent of fine material which would not be caught by the hair^
of the nymphal apparatus, which would mean that 70 cc?
ne TTedT. Tu 'f'"" '".^'^^^^ '"'""^^ "^^ the plan i
of." n f . ^ ^^"i^ accordingly indicate that at a velocity
scute tt ''•"■ -'^"^ -^'"^ '' ^^•'^'^'•^ «" ^" ^'■ea of 5..6
square mm. in sixty minutes 7.0 cc. of food material. \o\v
Clemens: Ecological Study of Chirotenetes 25
u
<:
u
s
<
00
M
r3
•<
3
2
3
2
I
3
I
3
3
3
i.
I
2
2
I
I
I
I
I
3
2
I
3
3
I
I
I
3
I
I
I
I
I
1
1-)
1
3
I
3
I
I
I
I
I
I
3
2
2
3
2
I
2
2
2
10
<
3
2
I
I
2
I
2
I
I
I
I
1^
C
3
"-1
3
3
3
2
I
I
I
3
I
I
I
I i
3 '■
j
' 1
I 1
1
1 ei
3
: <
Navicula
3
3
I
2
3
I
I
I
I
I
I
2
2
I
3
I
I
3
I
2
2
I
I
I
I
I
I
2
I
I
3
2
1
I
1
I
I
3
2
3
I j 2
-j
Cymbella
I
Mclosira
I
I
1
3
3
I
I
t
i
3
3
i '
Synedra
Cocconcis
I
Meridion
I
Gomphonema
Tabellaria
Gyrosigma
Cosmarium
Scenodesmus
Closterium
Pediastrum
Straurastrum
Protococcaceae
Cyanophyceae
I 2
Chantransia
I
2
1
3
Cladophora
I
Spirogyra
i I
1
llothrix
Microthamnion
2
Higher Plant Tissues. . . .
Euglena
3
2 '
i
3
3
3
Diplopiirys
Ciliata
Rotifcra
: I
I
Crustacea
Insecta. . . .
!
I
26
Clemens: Ecological Study of Chirotenetes
in area, il a nymph lives m a current of i . 5 feet per second
ba'ske't" oT^' ""frJ""'' ^'7'' '^ ^^"-^^ - thTplancton
basket 05 cc. of food material. The capacity of thai portio!
Tntl t- f "'^'^ '^"^' ^•■°'" ^^^ "^^"t'^ ^° the end of the S
mtestine of a mature nymph was then calculated as .00^5^'
This would mean that this portion of the alimentary canai
m:;^rial' 'tT;'/"?? ^'f \*'"^« '" ^-'- hours w-^hr
^Ta -u^ ^^"'*' °^ °*''^'' ^^t^'^es with calculations as
just described are given as follows:
Date
1915
June 25
" 29
July 6
" 13
Aug. 12
Available food per
8 »q. mm. in 12 tirs. at
i-S ft. per set.
Times capacity of
alimentary tract
050
8
097
15
041
6
048
7.5
066
10.2
After heavy rains
After heavy rains
These results are estimates but conservative ones
They show that there is a considerable abundance of foS
material coming down in the stream even when condidons
are adverse that is. following flood time. Doubtless th
to'' whlhT' '"r""^"^^ f '"^ "' ^'^^' S™-^h« - the one
to which they chng, so that the plancton catch (includine
particles of Wgher plant tissue and some animal material
may be considerably augmented. 'tit^nai;
No calculations were made during the winter but during
this season the creek is full of diatoms. All the stones "nd
rocks are covered with a thick brown velvety covering of
HSLTe:sThrnne^.re;^^ '^^ ^^'^ ^^^'^ ^^ ^-
mad^xs:-: l^^rs^^s;^- ^\:z
difficult because of the fact that the materials were so veo
finely ground up. Diatoms were found at all times, but wc?e
parhcu ariy abundant from September to April and includ^
a.I the forms listed in the plancton catches. Particles of fiS
Clemens: Ecological Study of Chirotenetes 27
mentous algae were recognizable in most of the mounts but
were difficult to identify. Cladophora and Microthamnion
were Identified and particles of a blue-green alga, probably
OsctUatcyrta. Of the smaller green forms a few specimens
ot Uostertum and Scenodesmus were found. Fragments of
higher plant tissues were common. Of animal remains two
rotifers were found in one individual, a small claw or mandible
of some undetermined form in another, SimuUum fan rays
and remains of Chironomid larvae in several and pieces of
chitin m a number. In all specimens examined there were
considerable quantities of c ^d particles. Needham Co<)
reports that for nine well-grown nymphs taken in Fall Creek
(time of year not stated) "plant remains constituted in all
cases fully half of the stomach contents." The plant food
consisted largely of higher plant tissues but mixed with this
were Cyanophyceae, Chlorophyceae and diatoms. Of animal
tood, four had eaten Simulium larvae and Caenis nymphs
seven had eaten nymphs of Ecdyurus maculipennis and one
had eaten of a small platode and a young nymph of Chiro-
tene.es. Morgan ('13) reports having found epidermisof roots,
/.ygnema, Gomphonema, may-flies and other insects in more
than ten specimens. It appears that the nymph of Chiro-
tenetes tends toward an omnivorous diet. No doubt a
considerable number of small animals such as small Simulium
and thtronomtd larvae and protozoans lodge on the nymph's
basket and are eaten as readily as the plant forms.
Relatum to the Oxygen and Carbon Dioxide Content of the
^,-~7SI'^'"'^^;,^"^'yses during 1914-1915 showed that the
water of Cascadilla Creek was quite normal as regards the
dissolved substances during that period. There was no
endence that the amount of pollution was harmful to the
organisms of the creek. The effect on the oxygen and carbon
dioxide content of a small amount of pollution in a stream
Howing several feet per second is probably very slight
Analyses from December i, 1914, to August 10, 1915. show a
comparatively high oxygen content throughout the year and a
ow carbon dioxide content— two factors of extreme importance
to an aquatic organism. The samples for oxygen determina-
28 Clemens: Ecological Study of Ciiirotenetes
tion were taken from the creek in the gorge in bottles with a
cX'h^ /^° •'• ^"^' ^^""'^ ''-'' ^"^-•^d t" «tand\.„-
^^. '^*r "'"?"'"' *" ^""^^' entrained bubbles of air t ,
escape and determinations were carried out at once. Thiro
^ a possibility that a small quantity of entrained air sti 1
remained in the bottle but the results obtained do n
represent the total amount of oxygen available, for t
tumbling waters hold a large amount of entrained ai wh c
would be of extreme value to the nymphs. In winter at o°
the results show the water to be almost saturated wi h
oxygen. In summer, although the amount per million cubic
centimeters has dropped considerably, still the water
frequently supersaturated. (Fig. 5.) The Ohio State Board
jrtcf JIK.
r;'la'nlI^„Xt';f^^\^°;;i:^u^„^."'^il^^ of ^.turation of water
~ nm^?,„,= f"".' '" r«"? !*■■ milllion.
amounts of saturation in parts per million,
of Health ('97) has reported water in Ohio supersaturated with
oxygen during August, September ..,d October Ihel^nl
(13) states that the carbon dioxide content is probaWy 1
best sing e index of the suitability of water for fishes beca.^.
"s oT tttaV" T r^ '"!.^.^-^'^ ^^^^^- Chemical ani-
ses of the Asater of Cascadilla Creek show a low carlxm
dioxide content throughout the year, especially in ZsT^Z
Clemens: Ecological Study of Ciiirotenetes 29
when during July and part of August the water was dc^•.,^d of
tnis ^3s*
The nymph ofChirotaictes obtains its oxygen supply by
means of tufts of tracheal gills. There are sexxn pafrs
attached to the posterior lateral margins of the abck.ninal
segments one to sexen, one pair attached to the bases of
the f<,rc coxae and one pair at the bases of the maxillae
An estimate of the g.ll area presented by the njniph was madJ
by counting the g.ll hlaments in a cluster and measuring t e
leng h and diameter of a single filament. The results thow
a gill surface of nbout 230 square mm. presented by a mature
nymph. The n.mph ,s thus well equipped for obtaining a
g<.(Kl oxygen .upply ,n that it possesses fore coxal and
maxillary gill tufts which are of unique occurrence among tlie
known may-fly nymphs of our fauna. The extensiNc gill
equipment probably bears some relation to the actix e habits
01 the nymph.
The following experiments were conducted to ascertain
if the nymphs of Chtrotenetes are dependent on current for
their oxygen supply. On June 27. 1915. there was put into a
large glass aquarium 2,000 cc. of water from Cascadilla
Creek, containing 8.3 parts per millitm of dissolved oxygen
and one part per million of free carbon dioxide at 18° C
Hyc nymphs were introduced into the water and on the
bottom of the jar was placed a clean stone to which the
nymphs might cling. On July 1 1 a rain added slightly to the
amount of water in the aquarium. On July 13 a nymph died,
and analysis of the water on July 14 showed 5.16 parts pei^
million of oxygen and three parts per million of free carbon
dioxide at a temperature of 2i» C. The remaining nymphs
dic^ on July 20, having lived in the aquarium twenty-four
days without food. Analysis on July 21 showed 9.9 parts
per million of oxygen and no free carbon dioxide at a temper-
ature of 15.1° C. Doubtless the nymphs had died of
star\ation.
For purposes of comparison 5,000 cc. of creek water had
been put into a large glass aquarium on June 17, 1915 with
no nymphs. Analyses of this v/ater were made as follows-
30 Clemens: Ecological Study of Chirotenetes
I9"5
June
17
it
18
n
24
July
14
11
21
24 hours
7 days
27 days
34 days
Temperature
20.2°C
17.2
no
21.0
15 I
Oxygen parta
per million
8.01
II. 6
9.68
7 49
9. II
Carbon Dioxide
parti
per million
«-5
■5
•5
2.1
.0
£/>eo?«. nlnVw ^*r'^«^^^^' ;hree Heptagenia and three
r?!^H-n n^^'^ ^""^^'^^y "y'^P*^^ f'-o"' flowing water of
the three F?'"''^ """'' ?"' '"'° '^^' ''^'- ^he next morLg
the three Epeorus nymphs were found dead. Of the remain
ZnZt:^ r T' '""' °" J"'y 30, the other two Sg
nv^ih J°/"^'"^?gos. On August 16 one Chirotenetl
nymph was st.Il ahve m the jar, having been able to live fo
twenty-six days m water which had been standing sixty da .
foUo^s" '''" ''^ ^'''^•°" °^ *^^ "y-P»^« gave'resultVs
1915
July 30
Aug
10
43 days
54 days
Temperature
20.0°C
17 O
Oxygen paru
per million
8.42
8.00
Carbon Dioxide
parts
per million
.0
15
Just before Cascadilla Creek enters the gorge section a
n "T."' ^^7'^ P''"^' ^^« been formS by a dam
m^^l^Jn -i ' ''^*- ' ^™"^ ^^^^'« P°"d failed to shot vm^
that ot the tumbhng water m the creek in the gorge The
cToTt?a"dumn rf" H ''' ^°"' ^'"^^ ^^'^^ ^^e'surfL Ind
Close to a clump of sedges m a situation where may-flies would
be hkely to occur That Chirotenetes nymphs do nTt Ihe
of cXn'dS '' ^'T" °' '^^.^ °' ^^^'^^^ *h-- - ex-
resuks o? the. ' "°'' ^^"^""^ •'^ '^^'^ °^ ^^"'•'•ent. since the
results of the aquarium experiments show that the nymphs
Clemens: Ecouxjical Study of Chirotenetes 31
are not dependent upon current for oxygen supply as are
Epeorus nymphs apparently, for the latter die very soon after
being placed m still water.
Associates.— In the classification of the ecological com-
munities of the stream, the nymph of Chirotenetes belongs in
the strata under the stones to the Hydropsyche or riffle
formation (Shelford, '13). Its associates in Cascadilla Creek
are as follows :
Ephemerida of the genera Heptagenia, Iron, Epeorus,
Ecdyurus, Ephemerella, Leptophlebia and Baetis.
Plecopterc of the genera Perla, Acroneuria, Neoperla and
Pleronarcys.
Neuroptera of the genera Corydalis and Chauliodes
Trtchoptera of the genera Hydropsyche, Helicopsyche,
Rhyacophyla, Leptocerus, Chimarrha and Polycentropus
Lepidoptera of the genus Eliophila.
Coleoptera of the genus Psephenus ("water-penny")
Dtptera o{ the genera Atherix, Chironomus, Diamesa,
Tanytarsus, Tabanus, Eriocera and Tipula.
Planarians.
Hirudinea.
Mollusca of the genus Ancylus.
On the smooth rock beds of the gorge, where the nymph
Chirotenetes occurs occasionally, are found larvae of
Stmuhum, Blepharocera and Hydropsyche and Ephemerid
nymphs of the genera Heptagenia, Iron, Epeorus and
Baetts.
Among the stones of the creek have commonly been taken
the blacknosed dace (Rhynichthys atronasus), the young of the
common sucker (Catostomus commersonii), Johnny darter
{Bolesomamgrum), the nigger chub (Exoglossum maxillingua) ,
the satin-fin minnow (Notropis whipplii), small common
shiners {Notropis cornutus) and the dusky salamander
(Desmognathus fusca).
Enemies.—Stomach examinations of some of the
associates of Chirotenetes show that the two chief enemies are
the large stone-fly nymphs, particularly Perla media, and the
black-nosed dace Rhynichthys atronasus. Morgan ('n)
of
7,2 Clemens: Ecological Study of Ciiirotenetes
reports having seen robins in Fall Crook gorge with the st t u.
hoaVs"' 7^0 "• 77'^ r -•'--«- P-iccting fro. ;,
htaks. The penod „f moulting is an especially helpless tinn
beam; t"h'"^''' %"' ""' -^"^'^ ^'"^ '""'^ -^' most iLbl
Decome the prey of enemies.
Severities of Stream Life.-Uiv in swift water is be.,,
vvith many chfficulties and dangers. Probably he no
to^^ng season or the nymphs of Chirotenetes is'^flood t" r.
Stones and rocks are moved by the fc.rce of the current u -'
dunng the spring flo.d the out-going ice scrapes an sVi
overXrork ;""/•• ?^ '""^""^"^ "^ stone.^ocks and
over the rock bed m the gorge of the stream at a time of hLh
water can be distinctly heard. The nymphs are iiTanger':
bcnng crushcxl or swept out in the current over water"al
into unsuitable situations. A pool about one hundrS and
fifty feet south of Fall Creek i. usuahy flood Jin spring U
portion of the creek being diverted through it. After su I
flooding Chnotenetes nymphs have been found in the ,
Another Illustration as to how the nymphs are carried a lout
expTrfments ''TV '''"•'■'^' '" ^^^' '""••- ^' ""^^^
the r?.X • T7 ''''" ""^ "'S'^t ^^"«^d the water in
the creek to nse and the trough set out for an experiment ^vas
earned about ten y.rds d.nvn stream without bei^ upset
The water was flowing over the trough to some extent and ,'
hXd 'Th: 1 "'h' ^h ^^^^'^^ •" ^'^^ ^'■-■^h ^^d airL:
smtted. The trough had contained thirteen almost mature
Ch^rotenetes nymphs, but when it was examined only tC
these remained, but twehe small Chirotenetes nymphs 7 t
mrn in length were found in the trough besides numer u
Baetts nymphs and a number of Ilydropsyche larvae
n„.n. V rT '^'o' ^^"^ "^'"P^' h^^'-^ to contend with large
quantities of si t. Samples of water have been taken iZ
the creek when it was loaded with sediment, the water f^\tZ\
and measured and the residue weighed after drying in th
a foHow^'' "^ ^"' ""''■"' '•"^^ "^^^ '•-"•^ obtained ar
Clemens: Ecological Study of Chirotenetes
33
Date
Amount of
sample
Weight of
aediment
Parts per
million
Condition!
1014
"
June 28
2200 cc.
13 8gr.s.
6200
Taken two Iionrs :iticr
very heavy downixjur
Aug. 20
2400
I.O
4>5
of rain.
Taken morning after a
Sept. 2
1900
3 4
r8oo
heavy night's rain.
Taken three hours after
1915
heavy rain.
Jin. 7
400
Taken at time of a mid-
July 5
2200
J 3
590
winter thaw.
Taken the day after
heavy rains.
Professor Chamot has stated that turbidities in Six-Mile
Creek frequently exceed 6,000 parts per million. Such
enormous amounts of sediment result from the hilly nature
of the watershed and the nature of the soil. The soil of
Cascadilla valley consists of silty, clayey and stony loams.
Heavy rams cover the hillsides with rivulets which brinji
down to the stream immense quantities of sediment The
water becomes yellow-brown in colour and so loaded with silt
that the earthy odour can be detected a long distance from
the creek particularly m the vicinity of waterfalls
Flood time too carries out to the lake the plancton of the
pools and ponds of the stream leaving the creek more or less
whlTtL 'T T^ °i **^°^ suspended organisms upon
^^h,ch the nymphs depend to a large extent for food. This
was showTi by p ancton catches taken before and after floods.
Needham ( 16) points out the dangers from ice particles
and anchor -^e" during the winter period
ProtecHon.~The nymphs of Chirotenetes receive protec-
Iin.WI,M .?""''' '° '^^ •°^'"'' «^^^^ °f ^hi^h they
fr;,^y ^^ the stones are in position, protection is
afforded from the force of the current, from larger objects
earned m the current, and where the space is small from
larger enemies such as fish. The nymphs no doubt escape
34 Clemens: Ecological Study of Ciiirotenetes
enemies by reason of protective colouring and agilitv
The chocolate-brown colour renders the nymph very inr.^n
sp.cuous on the dark coloured rocks of the stream Uxl, and the
ability to dart cjuickly from place to place by means of stnm'^
strokes of the abdomen and fringed setae is of deci,l,,i
advantage. Nymphs in a current of water in a trough haw
been observed to loosen their hold allowing the current to
carry them down a short distance and then to catch t!,
bottom or side of the trough again. Doubtless sucli a
procedure is used as a means of escape.
Regeneration. —The nymphs possess the power to rc^n ti-
erate certain parts. Frequently it has been observed that a
nymph lacking a leg will after moulting possess a small k^
How many instars are passed through before the leg attaiin
normal size has not been determined. The ability to rcytn-
erate a foreleg is of vital importance to the nymph.
The Subimago
Emergence.— There comes a time in the life of the nymph
when some stimulus causes it to crawl up the side of a stom
out of the water. The stimulus is probably supplied In a
number of agencies of which the maturation of the sexual
elements is doubtless the chief. The nymph crawls out just
above the surface of the water. In a few seconds convulsi\e
movements pass through the body, the head and thorax split
along the mid-dorsal line and the body of the subimago slips
out on to the stone. As soon as the wings are freed, they arc
spread, and at the same time the legs are extended so as to
support the body of the insect. It soon takes a few steps nr a
little jump and the alxlomen and setae are freed. After
a few movements of the wings, legs and setae, the subimago
flutters upward into the trees. Where no trees are near by
they often flutter upward out of sight. The body of th't
subimago sometimes slips out on to the surface of the water
and is carried down stream some distance standing on the
surface film. A wave occasionally submerges the subimago
or sweeps it away before it has freed itself from the old n> m-
Clemens: Ecological Study of Ciiirotenetes 35
phal skin, thus ultimately bringing it to its death. Trans-
formations occur in greatest numbers during the late after-
noon and evening but some occur in the morning. The
peri(xlofemergence is rather cxtendfxl. The eariiest observetl
emergence was on June 6 and the latest September 8, with the
greatest numliers in June and July. Morgan ('11) reports
cmergings in great numbers in May, 1910.
Factors affecting the length of the Subimnginal period.—
The subimaginal peri(xl is one of quiescence. The subimagos
remain quietly on the leaves and twigs of the vegetation
l)or(kring the stream. They take no food, the mouth parts
bemg degenerate. This condition prevails normally from
twenty-four to thirty-six hours, at the end of which time the
.subimago moults, and the may-fly takes on the adult form.
A set of experiments was carried out to determine the effects
of temperature, light and humidity on the length of the
subimaginal period. Three Iwll jars were set up. In one was
placed a tray of calcium chloride, in another a tray of water
and saturated blotters. The third was used as a control.
Hygrometers hung in the jars showed that in the first the
relative humidity was about 32 per cent, in the second
practically at saturation, and in the third 66 per cent.
Subimagos as they emerged were put into small wire cages.
A male and a female were put into each cage and the
cages put under the bell jars. Two series are given as
typical :
Jar— low humidity (32%)
9 emerged 12:25 p.m. Aug. 14, trans. 8:30 p.m. Aug. 15
, =32hrs. 5min.
(f emerged 12:40 p.m. Aug. 14, — died.
Jar— normal humidity (66%)
9 emerged 4:18 p.m. Aug. 14, trans. 9:00 p.m. Aug. 15
= 28 hrs. 40 min.
cf emerged 4:10 p.m. Aug. 14, trans. 9:00 p.m. Aug. 15
= 28 hrs. 50 min.
36 Clemens: EcoLotiicAL Study of Chirotenetes
Jar—saturation (ioo%) _
9 emerged 5:20 p.m. Au-^. 14, trans, i :oo a.m. Aug. 16 i ^'\
cf emerged 4:50 p.m. Aug. ,4. trans. .o.Jp.L^Aug." "f B ?
cT emerged 4:50 p.m. Aug. 14. trans. 1,:,^!^.' Au'g'""'
' 30 hrs. 25 niin. |f Cag
0
Jar— low humidity (35%)
9 emerged 5.15 p.m. Sept. 10, trans. 6:40 p.m. Sept. 12
c^ emerged 5.15 p.m. Sept. ,0. trans. 6:3o''rTSpt'n"-
= 49 hrs. 15 niin.
Jar— normal humidity (50%)
9 emerged 4:15 p.m. Sept. 10, trans. 4:10 p.m. Sept. 12
9 emerged 3:55 p.m. Sept. 10. trans. r.SOpL^'^pt'it
= 48 hrs. 55 niin.
Jar — saturation (95%)
9 emerged 4:25 p.m. Sept. 10, trans. 4:45 p.m. Sept. 12
c^ emerge! 5:05 p.m. Sept. 10. trans. 5:05%'M.tpr,T'"-
= 48 hrs. o min.
Other series brought out the same results, namely that
indmdual vanations were greater than the variations amc.g
efforf'TliT"*' ^'^'■\then conducted to determine the
effect of darkness on the length of the subimaginal periml.
wo^oT. V"''' ^ ^'"^'"F"^^ ^^-as obtained. The subimagos
nr.h?"'''l'? !f 'r^ ^^^"^ ^^'"^ «f ^Wch were put
he I^^ r'' •' dark-room and others on a window-sil in
sunlight "^ '" '^"^ ^"^^' ^'^^'' ^^ t»'"^« Partly in the
I Clemens: Ecoloc.ical Study of Ciiirotknetes 37
I
I Cage in light.
I d' emerged 4:10 p.m. Aug. 14, trans. 9:50 p.m. Aug. 15
! „ , =29 hrs. 40 min.
9 emerged 4:45 p.m. Aug. 14. trans. 1 115 a.m. Aug. 16
«=32 hrs. 30 min.
Cage in dark room.
cf cmergctJ 4:55 p.m. Aug. 14, trans. 12:20 p.m. Aug. 15
- , . =31 hrs. 25 min.
9 emer-cd 5:20 p.m. Aug. 14, trans. 12:30 p.m. Aug. 15
= 31 hrs. 10 min.
Other experiments gave similar results, showing that darkness
has no effect on the subimaginal period.
During the time these experiments were being conducted
the temperature varied considerably and a decided lengthen-
ing of the subimaginal period was noted when the temperature
of the air lowered and a shortening of the period as the
t-, neraturr rose. For example, on September i and 2. 1914,
the temperature rose to 28.3° C. and the subimaginal pr>riod
lasted 22 to 25 hours. On September i :, 1914. the tempera-
ture dropped to 15.5" C. and the period lasted 48 to
49 hours. A difference of 1^.8° C. had doubled the
length of the subimaginal life. A number of subimagos
were placed in a cage which was then placed in the ice box of
an ordinary refrigerator where the temperature was 8° C
The subimagos lived four days before transforming and some
failed to transform. The length of the period thus varies
greatly with the temperature but not with humidity or light.
Enemies.— The chief enemies of the subimagos are birds
and spiders. Birds have been observed to fly out of the trees
bordenng the creek and catch the subimagf)s fluttering up-
ward after emerging. All tree-inhabiting insect-eating birds
doubtless feed upon the subimagos. \Iany subimagos are
caught in spider webs. A fence along Fall Creek near Forest
Homo village usually has a great number of spider webs
hlhng its spaces. One afternoon a large nun. ber of subimagos
were emerging from the creek and a strong wind carried them
38
Clemens: Ecological Study of Chirotenetes
toward the fence. Every web along the fence had on. ,
2Z anr-"r ^"'r^^^^ ^^"^ht in the Zhes h" U:
sists^tfi^f ' °"ly P^tection for the subimago con-
sists in Its dull colour and its quiescent hah;t« A o,.t-
on the vegetation is usually diSt to detect!' "''
The Imago
and twltortho"7-^' '^' subimaginal moult, the h.ad
'he win's \i . '"^"1''^" ''?' ^'""S ^'^^" mid-dorsal line,
tnt AMHgs are spread almost horizontally and with i f.w
cc n racfons of the body the adult form ap^Irf W 1
ransforn,a ,on occurs on a vertical surface the bodv
tl S" '?.?' t"" ^"'^'^^^•^^^ -^'l the wings andV;
arc freed and then by movements of the wings t'le bod v i"
The adult'thrl ^!r ''^^ ^7 ^'^'^^ ^« ^-P th?:.i:ct atv :
^y"'tthc;n walks away from the moulted skin.
teristic of t7e ^^"""^ '' ""l ^^'"'''r'^^' have a flight charac
icnstic ol the majority of may-fl cs. They aooear ovr>r thp
nignttal., in small swarms of thirty to fifty individinl^
SLsdonSTi^ ^^^''.' T^ *he body horizontal The
down the creek t' T'' '" '^T ^'^^'' ^"* ^^ ^^"^^^ "P -'^
uown tne creek in long undulations. What factors indiire
t mTy'b: tif r h • ':• ^'^' T?'"^ ^^^^ -t belrdetermt
detSn^d bv n./' 'rr^^^y '^ '^" ^f^^t' having been
aettrmintd by natural selection, or it may be a neirativlv
When'T T"'^"^^ ^^"-"^ «-•■ f-- the nymphal ral'"
W hen a feniale enters a swarm of males she is quickly caudit'
by a male flying up beneath her. The male Xces his Ion
SiisToTcer '"xh"^^ r' '^?^ ^"^ graspXibi!;;:„^
oaer to J,^ n'^h . w' ^l^'^u"? °^ ''^^ ^"^^ ^^ the male in
oakr to gra»p the body of the female with the forceps brings
^ Clemens: Ecological Study of CiiiKoTE.xErEs 39
, the penes in position to be inserted into thr opciiiiif^s of thr
oviducts at the apex of the seventh abc- )minal scgn^, ■ t
Copulation lasts twenty-five to sixty secor s. The o)i -ies
do not nse high but remain at almost constan. .vol, fr^ que.jtly
making quick turns and occasionally sudden drops The
male in separating lets go his hold with the forelegs first and
tinaily with the forceps. Apparently the male returns to the
swarm while the female flies up and down the stream in long
undulations and soon begins ovipositing.
The mouth parts of the imago are degenerate and no food
IS taken during the short aerial life. The alimentary canal
however, is not degenerate but is filled with air and ser\es
as a buoyant organ (Sternfcld, '07).
Oviposition.—Prcceding oviposition the eggs make their
appearance from the openings of the oxnducts and form a
spherical mass which is apparently held in position by the
bending forivard of the sternal prolongation of the ninth
abdominal segment. The eggs are held together by very
fine strands of a viscid substance. The female flies oxer the
water unth long deep undulations carrying the greenish egg
mass and dips to the flowing water so that the egg mass is
carried away in the current. The eggs scatter somewhat in
the water and adhere to objects by means of the viscid
>irands.
The Egg— The egg is almost spherical with a diameter
r^ '"'??• . . . '^ S''^^"»sh in colour when mature, with the
surface divided into very small polygonal areas and slightly
roughened, ihe egg complement consists of 1,900 to 2 000
eggs. It was found that at a temperature of 22 5 to 25° C
they hatch in about fourteen days, while at a temperature of
13 ^.m twenty-five days. In the eggs ready to hatch the
eyes and ocelh of the embryos can be seen moving up and
down. After a considerable period of movement of the head
m this way, a crescentric slit appears on the egg shell at the
I IMnnt where the head has been moving, and then the head
J- ..ushes out through the opening. Soon the tips of the
y antennae are freed and extended. The pairs of legs follow
m
ession accompanied by considerable movement of the
40 Clemens: Ecological Study of Chirotenete^
moro fh/ ^WP"^7 and the setae; and in two min, t
more the nymph is able to shake off the egg shell T
size. They moult six days after hatching and still show
signs of gil s but the forelegs possess a few hairs alonTr
inner margins. It was found that the eggs o CW S.i !
could be artificially fertilized. The testes TthLmZJ'^^^^^
put into u^ter m a Syracuse watch glass and t^asec
about gently for a few minutes. The contents of thf. iv ./^
glass were left standing for an hour, then he .vae "a
poured oft with the bits of tissue resulting from the dissection
Fresh water was poured over the eggs and the wltl
covered and kept on the laborat:i?Sbre The^ggf bf: ^
to^hatch ele^en days later and continued to do T^Z
rnr^Jf"''^^ ^//^/^--How long the adults live under normal
conditions and whether males return to swarm a ^con U
third evening ha . not been determined. Reared imrgoTL
out of doors in . large wire cage in which was ^ut a lea
branch of a tree, li v^ed four and one-half days. ^
Summary
The results of the investigation are as follows-
I. The nymphs of CAi>o/g«e/e^ show a very decided
habitat preference for the lower surfaces of stonesTnd ruW ,
as against smooth open sheets of rock, and a slight preferen
for rubble as against small stones. pr«-itrcnce
^' Jk^ "y"iphs are negatively phototactic
K ^:J.u "^"P^' "^^ »" a very much dminished current
beneath the stones and rubble of the stream
4- The nymphal form of body is well adapted for a more
or less active life in running water.
5- By means of fringes of hairs and bristles on the
fcrelegs the nymphs are able to strain out suspended organic
materials of the stream for food purposes.
Clemens: Ecological Study of Ciiirotenetes 41
6. The suspended plant and animal forms in the current
arc sufficient m amount to supply the food requirements of
the nymph.
7. The water of Cascadilla Creek throughout nine months
was neither excessively polluted nor contained excessive
amounts of dissolved substances, so as to be harmful to the
nymph. The oxygen content was high and the free carbon
dioxide content low.
8. The nymph is not dependent on current for oxveen
supply. ^ **
9- Temperature has a very marked effect on the length of
thesubimaginal period, while humidity and light have no effect
10. The eggs of Chirotenetes can be fertilized artificially.
It appears that food has been the factor determining the
habitat of the nymph. With special equipments in bodily
structure it has pushed out into the current and made use of
the current to bring it food. Out in the swift water it has
taken to the lower surfaces of the stones and rubble for
shelter from the dangers accompanying life in swift water and
tor protection from enemies.
While the activities of the nymph are concerned primarily
\uth the acquisition of food, the activities of the adult are
concerned with reproduction. The degeneration of the
mouth parts, the inflation of the alimentary tract, the well
developed wings, the elongated forelegs and large compound
eyes of the male are modifications tending to insure the
perpetuation of the race.
42 Clemens: Ecological Study of Chirotenetes
Literature Cited
Morgan, Anna Haven.
191 1. May-flies of Fall Creek. Ann. Ent. Soc. Am< r
vol. IV, pp. 93-126.
1913- A Contribution to the Biology of May-fliiN
Ann. Ent. Soc. Amer., vol. VI, pp. 371-413,
Needham, James G.
1905. May-flies and Midges. N.Y. State Museum Bui!
86, pp. 17-36.
Needham, James G., and Lloyd, John T.
1916. The Life of Inland Waters. Ithaca, N Y
Ohio State Board of Health.
1897. Preliminary Report of an Investigation of Ri\-( rs
and Deep Ground Waters of Ohio as Sources of
Public Water Supplies. Cleveland, Ohio.
Shelford, Victor E., and Allee, W. C.
1913. The Reactions of Fishes to Gradients of Dissolvwi
Atmospheric Gases. Jour. Exp. Zool., vol. xn
pp. 207-266.
1913- Animal Communities in Temperate America as
Illustrated in the Chicago Region. A Study in
Animal Ecology. Geog. Soc. Chicago. Bull s
Stemfeld, Richard.
1907. Die Verkummerung der Mundteile und der
Funktionswechsel des Darms bei den Ephemcr-
iden. Zool. Jahrb. Jena, Abt. fur Anat. und Ent
vol. XXIV, pp. 415-430.
Wodsedalek, J. E.
1911. Phototactic Reactions and their Reversal in the
May-fly Nymphs Heptagenia inter punctata. Biol.
Bull., vol. XXI, pp. 265-271.
Clemens: Ecological Study of Chirotenetes 43
Explanation of Plates
Plate I
Fig. I. Nymph of Chirotenetes albomanicatus Needham.
2. Pitot-tube as used in Cascadilla Creek.
Plate II
3. Upland portion, Cac^ailla Creek.
4. Upland portion, Cascadilla Creek.
Plate III
5. Gorge portion, Cascadilla Creek.
6. Gorge portion, Cascadilla Creek.
Plate IV
7. Cascadilla Creek after descent into Cayuga Valley.
8. Flats portion, Cascadilla Creek.
Plate V
9. Winter conditions, upland portion, Cascadilla Creek.
10. Flood conditions, upland portion, Cascadilla Creek.
PLATE I
Fig. a. — Pitot-tubeas used in Cascadilla Creek.
I'l.ATK II
Fiu '.i. — I'pland portiDn. Cascadilla Creek.
Ki«. I.— I'pland |H>rt)oti. ("ascaililla Creek
PI ATK III
FiK. .">.— Ciorne iKirtion, Casiadilla ('rcik.
Fig. t). — Gor^e portion, Cascadilla Creek.
91
I
I' IK IV
KIk. 7 —Cascaililla Criik aittr ili'Mint iiiiii (aviitia \alli-
Fig. 8. — Klats iiortion. C'ascadilla Creek.
PLATE V
F'K. !l. -Winter conditions, upland portion. Cascadilla Crwk.
Kig. lO.-Klood conditions, upland portion. Cascadilla Crctk.