STRAITS POND STRAITS POND MIDGES:MIDGES:

Biology, Ecology, and Biology, Ecology, and Problem PopulationsProblem Populations

Straits Pond inhabitants:Straits Pond inhabitants:

Anadromous/Catadromous/ Amphidromous fish

Migratory shorebirds and waterfowl

Invasive plants and animals– Ailanthus altissima– Phragmites australis– Swans

Three-Spined Stickleback

Invasive plants …

Tree of Heaven Ailanthus altissima

Invasive species …

Straits Pond invertebrates:Straits Pond invertebrates:

Aquatic beetles Dragon/Damselflies

– Familiar Bluet– Big Bluet ?– Seaside Dragonlet– Needham’s Skimmer ?

Periwinkle Littorina sp. Green Crab C. meanus

COLEOPTERA: DYTISCIDAE

Uvarus sp.

Skimmer Dragonfly Larva

ODONATA: LIBELLULIDAE

Straits Pond invertebrates:Straits Pond invertebrates:

Flies (Diptera)– No-see-ums

(Ceratopogonidae)– Greenheads

(Tabanidae)– Craneflies (Tipulidae) – Midges

(Chironomidae)

MIDGESMIDGES

Abundant and ubiquitous– Inhabit all aquatic habitats

Adults do not bite Significant food source for

many other species Pollution-tolerant

Midge TaxonomyMidge Taxonomy

Insect order Diptera, or “True Flies”

Family Chironomidae– 20,000+ species– >350 sub-families– >2,000 spp in N.A.

Aquatic dipteran larvaeAquatic dipteran larvae

Merritt & Cummins, 1996Aquatic Insects of N. America

GENUS:GENUS: ChironomusChironomus Multivoltine - produce 1

to 4 generations each year Larvae are detritivores Larvae burrow, build U-

shaped tubes– Protection– Respiration

Body fluids contain high-affinity hemoglobin

C. decorus C. ripariusC. plumosus C. dorsalis

>20 spp. in N.A.

ChironomusChironomus life cycle life cycle Eggs hatch within 3 days Larvae live 5 - 50 days

– Temperature– Food availability

Depth preferences Overwinter in bottom

sediments in mid-larval stages

ChironomusChironomus larval larval ecologyecology

Associated with soft upper sediment layers Densities correlated with organic content

– Consume bacterial and fungal components

Lower densities found in gravel (ponds) Relatively drought and freeze tolerant

– Do not migrate during dry/cold spells

Brief - 2 to 5 daysRemain in larval tubeFloat to surface before emergence

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Pupal stagePupal stage

Pupal stagePupal stage

Merritt & Cummins, 1996Aquatic Insects of N. America

Adults live a few days to weeksFeed on nectar, or do not feedFemales produce one batch of eggs

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Adult stageAdult stage

Adult stageAdult stage

Merritt & Cummins, 1996Aquatic Insects of N. America

Super Floss Chironomid

Courtesy of Washington Fly Fishing Gallerywww.washingtonflyfishing.com

Factors contributing toFactors contributing toproblem populations:problem populations:

Stagnation– Warmer temperatures– Lower Dissolved Oxygen concentration

Nutrient loading– Septic systems and fertilizers … N, P, K– Decayed algae and plants … C

Problems & SuggestionsProblems & Suggestions

Annoying swarms gather in backyards

Adult midges are attracted to lights

Food is abundant Larvae thrive in harsh

environments

Beware of “bug-zappers”– Attract more insects– Kill beneficial spp.

Use yellow bulbs Reduce nutrient sources

– Lawns/Septic systems– Decaying plant material

Circulate/aerate water

Alternative control Alternative control methodsmethods

Manual removal of detritus Bacterial breakdown of

organic sediments

Alternative control Alternative control methodsmethods

Wind or solar powered water aeration

Introduce predators– Dragonfly larvae?– Bream

Caddisflies23.4%

Other Diptera20.6%

Stoneflies14.3%

Crustaceans12.8%

Beetles3.8%

Chironomidae14.8%

Dragons and Damsels

1.4%

Mayflies4.9%

Miscellaneous1.9% Molluscs

0.5%

Alder/Fishflies

1.7%

Figure 1. Freshwater streams

Estimated percentages of aquatic invertebrate taxa

Estimated percentages of aquatic invertebrate taxa

Other Diptera25%

Crustaceans15%

Molluscs12%

Miscellaneous10%

Beetles6%

Dragons and Damsels

2%

Chironomidae30%

Figure 2. Tidal ponds

Fish– Feed on aquatic stages– Most effective predators

Waterfowl– Feed on aquatic stages

Midge PredatorsMidge Predators

Dragons and Damsels– Consume all stages– Charismatic

Diving Beetles– Voracious consumers

of aquatic stages– Tolerant, prolific

Microorganisms– Fungi, Bti

Midge PredatorsMidge Predators

Seaside Dragonlet

Erythrodiplax berenice

Needham’s Skimmer

Libellula needhami

Swallows and Swifts– Forage on mating swarms

Bats– Feed in open areas

Midge PredatorsMidge Predators

Looking ahead …Looking ahead …

Monitor beneficial organisms– Vertebrates– Invertebrates

Promote scientific research– Local schools– UMass Boston

(Biology, ECOS)? Adapt