STRAITS POND MIDGES: Biology, Ecology, and Problem Populations

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: 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: Flies (Diptera) – No-see-ums (Ceratopogonidae) – Greenheads (Tabanidae) – Craneflies (Tipulidae) – Midges (Chironomidae)

MIDGES Abundant and ubiquitous – Inhabit all aquatic habitats Adults do not bite Significant food source for many other species Pollution-tolerant

Midge Taxonomy Insect order Diptera, or “True Flies” Family Chironomidae – 20,000+ species – >350 sub-families – >2,000 spp in N.A.

Aquatic dipteran larvae Merritt & Cummins, 1996 Aquatic Insects of N. America

GENUS: Chironomus 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. riparius C. plumosus C. dorsalis >20 spp. in N.A.

Chironomus life cycle Eggs hatch within 3 days Larvae live days – Temperature – Food availability Depth preferences Overwinter in bottom sediments in mid-larval stages

Chironomus larval ecology 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 days Remain in larval tube Float to surface before emergence Pupal stage

Merritt & Cummins, 1996 Aquatic Insects of N. America

Adults live a few days to weeks Feed on nectar, or do not feed Females produce one batch of eggs Adult stage

Merritt & Cummins, 1996 Aquatic Insects of N. America

Super Floss Chironomid Courtesy of Washington Fly Fishing Gallery

Factors contributing to problem populations: Stagnation – Warmer temperatures – Lower Dissolved Oxygen concentration Nutrient loading – Septic systems and fertilizers … N, P, K – Decayed algae and plants … C

Problems & 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 methods Manual removal of detritus Bacterial breakdown of organic sediments

Alternative control methods Wind or solar powered water aeration Introduce predators – Dragonfly larvae? – Bream

Figure 1. Freshwater streams Estimated percentages of aquatic invertebrate taxa

Figure 2. Tidal ponds

Fish – Feed on aquatic stages – Most effective predators Waterfowl – Feed on aquatic stages Midge Predators

Dragons and Damsels – Consume all stages – Charismatic Diving Beetles – Voracious consumers of aquatic stages – Tolerant, prolific Microorganisms – Fungi, Bti Midge Predators

Seaside Dragonlet Erythrodiplax berenice

Needham’s Skimmer Libellula needhami

Swallows and Swifts – Forage on mating swarms Bats – Feed in open areas Midge Predators

Looking ahead … Monitor beneficial organisms – Vertebrates – Invertebrates Promote scientific research – Local schools – UMass Boston (Biology, ECOS)? Adapt