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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 commc stream insect illustra on the nympli on this biologi T] invalu; given ( Ge catus h New \ stream chosen 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 ^ s 3 u M o u til . > 0 M Ul u 3< « M — w — J, 7 1 V f i a' 3 5' -• I J > > ■J r > > num watt' 4. in e 0 0 c C ■ 3 c 0 ^1 0 ^a 0 ;m CM u e 0 0 0 o di-fin nymi f.-om giver pt C O Oc » « - c •a M Cm 3 =^ *. in M K< Kl \C M i- - i. f 3 b b c b -ji -I c = oi e 0 b M - K. CM -.? 0 VI 0 0 -"I ■ wati' corrt" dicat amm alkal Vi V* \0 O -sj - 0 0 0 0 O 0 0 C 0 0 ?*-«■*-- >J Kl a- c ^ 'J< 5^ ix C*> O .^i ^ IJ iu - IJ - - u '1 Si C> Cfl C en To r If O ^J r^ tn C^ K* 'C M'tfj I't £ i §, 0 ;, 0 2 = 4- *1 -5 ! 1 4- - '■JX ■5 * ^a a ' 2 g s i 1! 5 7 L b n •-* VI en Cm 2 7 * b j> b tin CM M U1 U1 M Cm in 0 ^' i oc 1 1 <2 i :f i^:j 2= ?DJ ■U CM W ffv K» " S O VO 00 doubt Figun If 760 m at the 1? 3 ' conter contcr J in Cas for th flurtii; 3 o 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.