Life of the No-See-Um: the Cacoa Tree Pollinator
The no-see-um is a fascinating benthic macroinvertebrate that goes through
a complete metamorphosis, involving the complete four stages of the life
cycle; egg, larval, pupal, and adult phase. Being less than 3mm long in their
adult phase they have rightfully earned their name as no-see-ums. Today we
will explore what happens after the no-see-um pupae leaves the safety and
familiarity of the water. And how does the no-see-um pupae transform into its adult form? To explore these questions, we’ll start at the very beginning-- when the no-see-um eggs are first laid.
An adult female no-see-um will lay as many as 450 eggs per batch and can lay up to as many as 7 batches of eggs during her lifetime. Eggs will typically hatch within 2 to 10 days along banksides and atop rocks within the water or even on aquatic vegetation. The amount of time it will take for development varies by species and is dependent of water temperatures and other environmental conditions.
Once hatched the larval stage begins and no-see-ums will go through four stages of development, also known as instars. The no-see-um larvae will develop out of the water along moist environments that include the stream bank and wet sand or mud.
No-see-ums will then pupate underwater where they will use specialized structures called respiratory horns emerging just above the water surface which allows the no-see-um to breathe and remain close to the water surface. This stage of development can last anywhere from 2 to 3 days and the coloration of the no-see-ums can vary from light yellow to dark brown.
In its adult form, no-see-ums are grey in colour and have wings that are patterned and covered in hairs. Mating occurs when adult no-see-ums swarm in large numbers in flight. Female no-see-ums will fly into these swarms where copulation occurs mid-air. Female no-see-ums will then go hunting for a blood meal and prey upon animals, including humans in order to obtain the nourishment needed to lay her eggs. Much like blackflies, no-see-um adults are attracted to lactic acid, carbon dioxide and strong perfumed odors. The complete cycle of a no-see-um can occur in 2 to 6 weeks or alternatively it can take up to a year. Again, life cycle stages and the period of development within each stage is heavily dependent on species type.
Fun Fact: No-see-ums have even been found on Mount Everest!
Fun Fact: No-see-ums and gull midges are the only two insects that help
pollinate the cacao plant, which produces cocoa beans used in the production of chocolate.
Interested in learning more about benthic macroinvertebrates and
how they can be used to measure the health of rivers and streams?
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Elements for Life. (2018). All about Cacao- The Origins of Chocolate. Retrieved from:
Carina is an Environmental Education Assistant with the Changing Currents Program at EcoSpark. She is passionate about aquatic ecosystems and educating young minds on the connections between land and water. She recently graduated with a degree in Environmental Studies from York University and a diploma in Ecosystem Management Technology from Sir Sandford’s Fleming College, School of Environmental and Natural Resource Sciences.