freshwater ecology

what is limnology?
The study of fresh or saline waters contained with continental boundaries including: lakes, inland seas, ponds, reservoirs, estuaries, wetlands, swamps, bogs, springs, vernal pools, tree holes, streams.
What is a limnologist? – a.

J. R. Vallentyne

Freshwater Institute, Winnipeg (1969) wrote in the journal Limnology & Oceanography “ A limnologist is a zoologist who, during summertime, studies chemical and botanical aspects of geologoical problems in readily accessible lakes, 15 m deep, located in the vicinity of universities”.
editor of L&O, E. S. Deevey and professor at Yale wrote
“The head of the world’s leading eutrophication project shows understandable nostalgia for those 15 m days. University lakes of his student days have now shoaled to less than 14-m depth.

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A modern limnologist is best defined as a biogeochemist and self-taught systems analyst, whose favorite systems are imbedded in an exponentially increasing matrix of septic tanks.”

F. A. Forel—“Father of Limnology”
a) worked on lake Geneva, Switzerland (1868) — coined the term limnologyb) wrote 3 volumes on physics, chemistry & biology of Lake Genevac) wrote first textbook on limnology in 1901
Louis Agassiz 1850
a) published “Lake Superior: Its physical character, vegetation & animals also founded the Museum of comparative zoology at harvard

A. Forbes 1887

published “The Lake As a Microcosm”
E. A. Birge early-mid 1900’s
“Father of American Limnology”–University of Wisconsin
Paul Welch
wrote first American text on limnology in 1935 “Limnology”- -University of Michigan
Franz Ruttner
wrote “Fundamentals of Limnology” in 1940 translated to English 1964
G. E. Hutchinson–Yale University-
wrote 4 volume “Treatise on Limnology” 1957-1973
R. G. Wetzel
published first edition of “Limnology” 1975–U of Mich, U of Ala, UNC

B. N. Hynes–University of Waterloo

published “The ecology of running waters” 1970. “Father of Stream Ecology”
J. D. Allan
University of Mich–published “Stream Ecology” 1995
Water Global distribution
1. ocean2. polar ice caps / glaciers3.

ground water4. FW lakes.

Molecular structure of water
a liquid crystal, not a true fluid.

– polar hydron bonds. matrix forms and remains a liquid

properties of water ..Density, temperature relations
stratification issues think about arctic diving – due to density , this is important ecology for ice to be on top and not in the water columon.

allows animals to escape danger under the ice. The greatest density is 4C m/unit vol.

properties of water – salinity relations
density issue – think about arctic diving. salt decreases freezing point The saltier the water, the more buoyant an object becomes.Very salty water is denser and will sink more; thus very salty water is found at the bottom.

Less salty water is less dense and will float on top of the more dense salty water.

properties of water …pressure
water is 350 times denser than air Density increases with depth
properties of water – turbidity
dissolved particulates, more turbid, more dense.
properties of water – viscosity
thickness, residence to flow
properties of water – surface tension
water strider ecology, hydron bonds orientation.

properties of water – temperature – specific heat
amount of energy required to raise one degree and cal.
properties of water – temperature – latent heat of fusion
ability to melt ice
properties of water – temperature – latent heat of vaporization
takes a lot of heat to vapor.water to stream = 540 cal/g thats a lot to melt / raise
aquatic life forms – Neuston
organisms that live on the surface
aquatic life forms – nekton
swimming creatures. e.g.


aquatic life forms – plankton
floater / can move around . maybe a meter in H2O coulum.
aquatic life forms – plankton – phytoplankton
net or macroplankton >200umnannoplankton 20-200umultra plankton 10-20umpicoplankton 0.2-1um
aquatic life forms – plankton – zooplankton
micro crustrations / e.g. rotifers
aquatic life forms – plankton – seston
anything floating in the water partical material in suspetion
aquatic life forms – plankton – trypiton
dead part
aquatic life forms -benthos
animals / plants that live on the bottom
aquatic life forms – Aufwuchs
periphyton- algae that grows on surface of plantsepilithon – organims growing on rocksbiofilms- on growers
Bacteria – general
omnipresent in the biosphere- can find anywhereprokaryotes – no organized nucleushas cell wall of peptido-glycansmost <5 micrometerspop.

increase rapidly by asexual reproductions.

bacteria- imporatance in ecosystem energetics and process -autotrophs
can convert inorganic to organic material
bacteria- imporatance in ecosystem energetics and process- photoautotrophs
use light Co2+H20 – carbohydrate using sun.
bacteria- imporatance in ecosystem energetics and process-chemoautotrophs
use chem, use inorganic chem reaction, use for carbohydrate sythesis e.

g. rust in stream bed. ocean = communities depend on chemoautotrophs

bacteria- imporatance in ecosystem energetics and process-hetroautotrophs
get energy from somewhere else – soaking up enery from environment.
bacteria- imporatance in ecosystem energetics and process-nutrient cycling
ammonia to nitriate
bacteria- imporatance in ecosystem energetics and process- decomposition (mineralization)
organic to inorganic
bacteria- imporatance in ecosystem energetics and process- waterborne disease organisms
typhoidcholeralegionelaagastroenteritisthese go through the population easy
cyanobacteria – bluegreen bacteria -NOT ALGAE ) – general characterisitcs
found in hot springs where there is lots of phosophous. prokaryotes – no organized nneucleouscell walls like bacteria _ e.g. – peptido-glycanspolysaccharide stored as glycogenunicellular, filamentous, colonialvery tolerant of harsh environmental conditionspopulations increase rapidly by asexual reproduction.
bacteria- imporatance in ecosystem energetics and process
-blooms and nitrogen
bacteria- imporatance in ecosystem energetics and process-consequences of blooms
ecologicalhuman concerns- anabaena flos-aquaemicrocystis sp.

both – toxic to humansaphanozomemnon flos-aquaetoxic to fish/humans

chlorophyta -green alage general characteristics
eukaryotes – can see nucleus- membrane bound cell wallscell walls of cellulosepolysaccharides stored as starch -unicellular, filamentous, or colonialpopulations may increase rapidly by sexual reproductionwell developed sexual reproduction-varietyimportant primary producers in most aquatic systems (photosynthetic)cannot compete with cyanobacteria in low N conditionsgood food for consumers
Dinophyta -dinoflagellates
produce red tide, produce oil to float. very huigh quality food for grazers due to oilsmay be limited by P and N like other algae but also Si02 (glass)unicellular flagellates with cellulose shell (theca)many produce red tides = toxic blooms in marine systemspfisteria blooms in estuaries due to N pollution threat to human health
mostly unicellular but some are colonialprotoplasm encased in SI02 (glass) shell frustule or theca
Diatoms – epitheca
upper half
Diatoms – hypotheca
lower half
Diatoms – girdle
protein band holding two halves together
eukaryotes – like higher plants , but cell walls made of CHITIN – has N in itcell walls mostly chitin
funig -saprotrophs
absorb Disvoled organic compounds from environment or parasities
fungi – obligate symbionts
as in lichens or mycrorhizzaw – symbolisis
fungi body forms – mycelium
for feeding and growth
fungi body forms – fruiting body
for reproduction
fungi – aquatic hyphomycetes
member of fungi imperfecti – no sexual reproductionfirst organisms to begin decay processes spread about via asexual spores.
higher plants “large plants”growing in lakes / streamswhereever there is H20 they grow”can choke off surface water ” Water willow” – helps form islands / land grows like strawberries – traps sediments. strong root system – common in southern rivers. many produce toxic chemicals, not much feeds on macrophytes are important sources of food for things that like dead organic matter. they take up a lot of nutrientscan regulate nutrientsgood for stopping sedimentation.

RotifersGeneral Features

a. 0.1-1.0 mm longb. body cylindrical, sac-like or worm-likec. body generally covered by a shell (lorica)d. most have crown of cilia (corona) used toswim and/or gather foode. mastax–chitinous “jaws”a) variously specialized for feedingb) important feature used to identify
Rotifers – ecology

locomotion–most swim at some stage inthe life cycle using coronab. feeding–many filter feed on seston butsome are predatorsc. habits–may be planktonic or benthic,single or coloniald. anhydrobiosis–undergo dehydration andform resistant cyste. periodicity–large, seasonal fluctuations inpopulation densityf. vertical migration–daily verticalmovement thru the water columng. trophic relations–primary consumers andpredators–important in food webs of mostlakes

Rotifers – life history

mictic cycleb. amictic cycle

cladocera “water fleas” -general features
a. 0.3-2mm longb. definite head; body (thorax & abdomen)enclosed in bivalved carapace(shell) ofchitin ending in a sharp spinec. pair of conspicuous compound eyesd. two pair of antennae: 1st small; 2ndconspicuouse.

many leg like appendages used inlocomotion & feeding

Cadocera (crustaceans ) “water fleas” – ecology
a. locomotion–”jump” thru water usingantennae like oarsb. feeding–planktonic forms filter feed onseston and select particles based on size.benthic forms may feed on detritus or bepredatorsc. habits–most species are freshwater,planktonicd.

periodicity–large seasonal fluctuations indensitye. vertical migration–daily verticalmovement in water columnf. cyclomorphosis–changes in shape insucceeding generationsg. trophic relations–primary consumersextremely important in food webs in manylakes, especially for larval fishes

cladocera “water fleas” -life cycle
a. most individuals are parthenogenicfemales thru most of the year producingmany young carried in brood chamberuntil development is overb. sexual females occur late in growingseason, brood 1 or 2 young, that may3become encased in a “resting chamber” or“ephippium” for over wintering.c. In some species, females over winter
Copepoda (crustaceans) copepods – gen.


a. 0.5 -2.0 mm long–some up to 5 mmb. body generally tear-drop shaped tocylindricalc.

body segmented with many pairs ofappendages–no carapaced. 1st antennae conspicuous, 2nd antennaeless soe. single median (nauplier) eye–nocompound eyes

cladocera “water fleas” -ecology
a. locomotion–also “jump” thru water usingantennae like oarsb. feeding–planktonic forms filter feed;benthic forms feed on detritus or arepredaceous; some are parasitesc. habits–most species are marine, about 10-15% are freshwater. There are manyplanktonic and benthic species and can befound in virtually all aquatic habitats andin moist soils.d.

Important in lake & stream food webse. periodicity–large seasonal fluctuationsf. vertical migration—dailyg. trophic relations–primary consumers– fedon by variety of invertebrate & vertebratesin lakes & streams

cladocera “water fleas” -life cycle
a. most species are sexual4b. release immature larvae that go throughnumerous stages before becoming adults–a marine-type life cyclec. many diapause (form a resting stage) toover winter or to avoid drying
Gastropods -snails- General features
a. most inhabit coiled shells made mostlyfrom calcium carbonate and protein–some(limpets) have cap-like shellsb.

size range from a few mm to severalinchesc. characterized by presence of radula (forfeeding) and foot (for locomotion)d. Prosobranchs have gills; Pulmonates havelungs

Gastropods -snails- ecology
a. feeding–most are scrapers–scrapesurfaces for food using radulab. habits–most are benthic or epiphytic;distributed widely in aquatic systemswhere there is sufficient calcium–generally absent in water with acid pH.

c. trophic relations primary consumers–provide food source for a wide variety ofaquatic predators and are very importantin food webs of most aquatic systems

Gastropods -snails- life cycle
a. Most are sexual–some hermaphroditic butcross fertilize.b. Females produce lots of eggsc. Most remain active over winter
bivalves- mussels and clams -general features

all freshwater forms inhabit a bivalvedshell composed of calcium carbonate &proteinb. size range several mm up to 12 inches ormorec. characterized by presence of large footused in locomotiond.

also characterized by presence of large gillused for:a) filter feedingb) gas exchangec) brooding eggs and/or juvenilesd) gill chamber irrigated by watercurrents entering thru incurrentsiphon

bivalves- mussels and clams – ecology
a. feeding–all freshwater forms are filterfeedersb. locomotion–most move about very littlebut can “crawl” on the surface or burrowinto the substrate using the muscular foot.Juveniles may move with water currentsc. habits–adults are benthic and generallyremain buried to one degree or another inthe substrate of lakes and some streamsd. native species very susceptible to siltationand toxicse. trophic relations– primary consumers–fedon by a variety of vertebrate predators instreams & lakes
bivalves- mussels and clams -life cycle – -spaeriidae- fingernail clams
Sphaeriidae–fingernail clams6a) most widely distributed of freshwaterbivalvesb) females brood embryos to juvenilestage and release
bivalves- mussels and clams -life cycle – -Corbicula -asian clam
a) exotic introduced at turn of centuryfrom Asiab) brood embryos to juvenile–very highbirth ratesc) serious biofouler
bivalves- mussels and clams -life cycle – -Dreissen – zebra musssel
a) Facultative marine exotic introducedUSA 1985—marine-type life cycleb) females release mobile veliger larvaec) highly invasive, stick to surfaces andeach other using byssal threadsd) super-serious bio-fouler
bivalves- mussels and clams -life cycle – -unionidae
a) many NA species rare and endangeredor threatened with extinctionb) brood embryos to glochidia which areexpelled and parasitic on particularspecies of fish.c) Failing to find the proper host fish,glochidia die within a short time.

d) glochidia on right hosts develop intojuveniles, drop off fish and take upresidence in sediments

oligochaetes- aquatic “earthworms” general features
a. segmented worms bearing setae (chitinousbristles)b. size range from a few mm to severalinches in length7c. most exchange gases across body wall thusbody wall is well supplied with capillariesd. blood contains hemoglobin to transportoxygen between exchange surface(skin)and tissues
oligochaetes- aquatic “earthworms” – ecology

feeding–most feed on organic material inthe substrateb. locomotion– move by crawling on surfaceor burrowingc. habits–most are benthic and burrow inthe substrate of lakes & streamsd.

many are tolerant of low oxygenconditions and toxic chemicals and havebeen used as “indicators” of organicpollutione. trophic relations–primary consumers–may be very important in some food webs

Branchiobdellida – branchiobdellids – general features
a. unevenly segmented worms that live ascommensals on crayfishb. size range 0.8 to 10 mm lengthc. mouth fitted with chitinous jaws suited forscraping surfacesd. posterior end fitted with sucker forhanging on to surfaces
Branchiobdellida – branchiobdellids – ECOLOGY

habits–live in various creases and creviceson crayfish and other crustaceansb. feeding–apparently feed on biofilmsgrowing on crayfishc. trophic relations–not particularlyimportant in most systems8

Hirudinea—Leeches1. General features
a. segmented worms (related to oligochaetes)that are dorso-ventrally flattenedb. mouth with chitinous jaws for predationand sucking bloodc. posterior sucker for holding on to preyd.

size 5mm to 18 inches

Ecologya. feeding-many are predators on a varietyof aquatic animals, many suck blood fromvertebrates, some are scavengersb. trophic relations–may be significantpredators in some systems– also eaten byvertebrates
Amphipoda—amphipods, scuds, or sideswimmers1.

General features

a. laterally flattened crustaceansb. large crushing “jaws” called mandiblesused for chewingc.

body divided into 3 regions (head, thorax& abdomen) and with chitinousexoskeleton that contains highconcentration of Cad. all body regions segmented with pairedappendages on each segment-most about 1cm

Amphipoda—amphipods, scuds, or sideswimmersEcology
a. feeding– most are detritivores but somemay feed on living vegetation–young feedon biofilmsb. habits–benthic–widely distributed on andin substrate and aquatic plants infreshwater systems including caves &9springs—cave species frequently endemican are thus rare & endangered. Manymarine speciesc. locomotion–”side-swimming” usingappendagesd. trophic relations–as primary consumers,very important in food webs, especially insprings & caves
Amphipoda—amphipods, scuds, or sideswimmerslife History
life Historya. sexual reproduction only–most breedcontinuously so you always find a range ofages(sizes) in specific populationsb.

like other arthropods, the exoskeleton isshed (molted) periodically and replaced–this is the only time the animals can growlarger–most species go thru about 10“molts” between birth and adulthood

Isopoda—isopods or sow-bugs1. General features
a. dorso-ventrally flattened crustaceansb.

also with mandiblesc. body in 3 regions, segmentation,appendages, & exoskeleton as inamphipods—most are <1 cm long

Isopoda—isopods or sow-bugsEcology
a. feeding-most are detritivores and/orscavengers–young feed on biofilmsb. habits–same as amphipods.

in fact,amphipods & isopods are almost alwaysfound together in springs & caves. Manyare endemic to specific springs or cavesc. locomotion–mostly crawl on and insubstrate & vegetationd. trophic relations–same as amphipods103. Life historya.

very similar to amphipods

Crayfish1. General features
a. relative large crustaceans ranging from 5up to 35 cmb. body divided into 2 distinct regions:cephalothorax (fused head & thorax) andabdomenc. 2 pairs of long antennae and 1 pair ofconspicuous compound eyes on headregiond. thorax with 5 pr walking legs, first pairenlarged chelipeds pincers) and coveredby dorsal shield (carapace)e. abdomen with paired appendages on eachsegmentf. exoskeleton of chitin with highconcentrations of Ca


2. Ecologya. habitats–wide spread in freshwaterincluding caves and groundwater whereCa is sufficient.b. Many live under large rocks, wood, etc.–others burrow in mudc. feeding– some graze algae, some shredleaves, some filter feed, most arepredators at times–call them omnivoresd.

locomotion–mostly crawl but can “jet”backward using the taile. trophic structure–omnivores that arefavorite food of many aquatic &terrestrial vertebrates

CRAYFISHLife History
a. generally breed once a year–femalebroods eggs under abdomen and carriesyoung around for a time after hatching.b. can only grow after molting .
A. General features of insects

body is divided into 3 distinct regionsa. heada) 1 pair of antennaeb) 1 pair large compound eyesc) 1 to several ocelli (simple eyes)d) complex mouth parts1) labrum-fused “upper lip”2) mandibles-paired3) maxillae-paired4) labium-“lower lip”b. thoraxa) three pairs of walking legs in larvae and adultsb) two pairs of wings in adults except for Diptera (1 pair) and some wingless forms.

Wings absent in immaturesc. abdomena) lack true appendages but may have external structures associated with reproductive system

insects- life cycles
B. Life Cycle Types1. General featuresa. most species have relatively long lived aquatic immatures.

b. Most species have relatively short lived terrestrial adults with notable exceptions.2. Holometabolous (complete) metamorphosisa.

life cycle has 4 stagesa) eggb) larva—up to 6 larval stages separated by moltsc) pupad) adult (imago)b. in some, all stages are aquaticc. in most, egg, larvae, and pupae are aquatic-adults are terrestriald. in some, egg & larvae are aquatic, pupae and adults are terrestriale. in some others, eggs, larvae & adults are aquatic, pupae are terrestrial.3. Hemimetabolous (incomplete or gradual) metamorphosisa. life cycle has 3 stagesa) eggb) larvae or nymph—may have up to 30 larval stages separated by moltsc) adultb.

eggs and larvae are aquatic, adults are terrestrial

C. Ephemeroptera—mayflies1. General features
a. nymphal body flattened or cylindricalb. generally with 3 cerci(tails) but some have 2c. plate-like abdominal gillsd. large compound eyes and noticeable antennaee. most have ocelli as nymphs

most are primary consumers–eat detritus or algae; a few are predaceousb. wide spread in lakes, streams, and other freshwater habitatsc. nymphs are generally considered to be sensitive to pollutiond. serve as food for a variety of invertebrates & vertebrates

Ephemeroptera—mayflies- life-history
a. hemimetabolousb.

nymphal life normally 5-8 mo with 12-30 instars; adults very short-lived(hours to days)c. last nymphal instar molts into sub-imago (winged but sexually immature)—wings are smoky rather than clear as in mature adultsd. Subs go thru an additional molt to become sexually mature adults only insect that molts after becoming winged.e. mating occurs in swarms, female dies shortly after laying eggs

D. Odonata–dragonflies & damselflies 1. General features
a. nymphal body of dragonflies broad & flat or thick and cylindricalb.

damselfly nymphs generally cylindrical and thinnerc. both with extendible, raptorial labia (lower lip) for prey captured. dragonfly nymphs have internal rectal gills; damselfly nymphs have external terminal gills e.

damselfly adult fold wings over back at rest; dragonfly adult wings remain spread laterally f. large eyes, small antennae

Odonata–dragonflies & damselflies – ecology
a. wide spread in lakes, stream, marshesb.

nymphs & adults predators c. adults display complex behaviorsd. nymphs & adults fed on by wide variety of predators

Odonata–dragonflies & damselflies -life history
3. Life Historya. hemimetabolousb. nymphs live 1-3 years; adults live up to 3 months c.

last instar nymph crawls out of water to molt to adult

E. Plecoptera—stoneflies1. General features
a. nymphal body cylindrical or dorso-ventrally flattenedb. nymphs always with 2 tails, no abdominal gills–may have coxal, cervical, or anal gillsc. large eyes, conspicuous ocelli, prominent antennae
Plecoptera—stoneflies- Ecology

Ecologya. generally restricted to clean, cool, fast moving streams, sensitive to pollutionb. nymphs predators or detritivores; most adults don’t feedc. adults poor flyers, secretived.

nymphs & adults important in food webs

Plecoptera—stoneflies – life history
3. Life Historya. hemimetabolousb. nymphal life 8 months to 4 years, adults short livedc.

last nymphal instar crawls out of water to molt into adultemerge at all times of year including winter, adults display courtship behaviors including “drumming” on substrate to attract females

F. Hemiptera—bugs1. General features
a. nymphs & adults have “piercing-sucking” mouth parts(stylet)– penetrate prey, release digestive enzymes, suck out dissolved insides b.

some highly adapted for swimming in water or “skating” on surfacec. many have long breathing tubes

Hemiptera—bugs- Ecology
a. nymphs and adults are predatorsb. many species have fused wings, never leave the water. Some do fly and are attracted to lightsc. more species in lakes but there are some “stream” species, some occupy hot springs or saline pondsd. many have scent glands with which they ward off predators
Hemiptera—bugs – life history
a. hemimetabolousb.

most have annual cycles

G. Megaloptera—Dobsonflies, alderflies – General features
a. larvae (called hellgrammites) with large, sclerotized head with prominent mandibles.b. abdomen soft, very long, each segment with paired lateral filaments (with some exceptions), and pair of terminal hooks.c. some with prominent abdominal gills at base of lateral filaments; others with dorsal breathing tubes near tip of abdomen
Megaloptera—Dobsonflies, alderflies – Ecology
2. Ecologya.

widely distributed in streams, lakes, springs, seeps b. voracious predatorsc. favorite food of many fish, each other, and other invertebrates and vertebrates

Megaloptera—Dobsonflies, alderflies -Life History
a. holometabolousb. larval life 2-4 years, adult life a few weeksc.

last instar larvae leave water, build a pupal cell in mud or old log and pupate.d. Adults totally aerial–lay eggs in cases over water- hatchlings drop into water and begin life e. Adults are very large and conspicuous

H. Trichoptera–caddis flies1.

General Features

a. larvae worm-like but with insect legs and many have highly sclerotized heads, dorsal shields on thorax, terminal sclerotized prolegsb. many have abdominal gillsc. adults resemble moths (have scales on wings) but fold wings tent- like over the back and have very long antennae
Trichoptera–caddis flies- Ecology
a. widespread in most freshwater habitats, some semi-terrestrial, some are commensals with estuarine crustaceansb. extremely diverse group with respect to functional feeding group: herbivores, detritivores, predatorsc. frequently most numerous and most productive invertebrates in streams thus extremely important in stream food websd.

many construct protective cases of materials ranging from silt to pebbles. many are silk-net spinners–show close affinity to Lepidoptera(moths & butterflies)

Trichoptera–caddis flies-life history
a. holometabolousb. larval life 8-10 months, pupae & adults relatively short-livedc. adults appear to produce pheromones for sex attractants again showing relationship to Lepidopterad.

last larval instar constructs silken pupal case, molts into pre-pupa, which then molts into pupa in the water.e. Emerging adult leaves pupal case in water and must swim to and break thru the surface film.f.

females lay eggs under water, then die

I. Coleoptera–beetles1. General Features

larvae take many forms–some resemble megalopterans, others resemble caddisflies.b. larvae characterized by heavily sclerotized head with sickle-shaped mandiblesc.

adult forewing modified as elytra (hard shell) that covers hind wing

a. widespread in all aquatic habitats including caves, hot springs brine pools b. larvae include: predators, scrapers, detritivores; adults samec. adults of most species remain in the water almost full time but can fly and are often attracted to lightsd. many adults have defensive glands that protect them from predation, but beetles are still important in food webse. beetles are the most diverse of the insect orders on land and in the water–it is difficult to make generalizations that apply to all groups
Coleoptera–beetles – life history
3. Life Historya. holometabolousb.

most larvae require 6-10 months to mature. last instars leave water and construct a pupal cell on land.c. most adults probably do not live very long in nature but can be kept alive in for years in the lab

J. Diptera–true flies1.

General features

a. larvae are legless and worm like–called maggotsb. adults take many forms but the presence of 1 pr wings sets them apart from all other insects
Diptera–true flies–Ecology
a. dipteran larvae are found virtually everywhere in freshwater; many are estuarine and many are adapted to living in hypersaline waters like the Great Salt Lake and the Dead Seab. adults are aerial creatures, many display complex mating behaviorsc.

dipteran larvae run the full range of functional feeding groups in aquatic habitats including cannibalism and parasitismd. adults range from DOC feeders to sucking vertebrate bloode. larvae of certain groups e.

g., Chironomidae, are often numerous under polluted conditions and are considered tolerant in general.f. dipteran larva & adults are almost always very important in the tropic dynamics of habitats they occupy

Diptera–true flies–Life History
a. holometabolousb.

most go thru 4 or 5 larval instars, construct a pupal case, and pupate in the water or damp habitats.c. some may pass from egg to egg in about 3 weeks and can have 5-10 generations per year; other have a single generation that lasts 6 months