Insects of the Credit

Insects of the Credit

Insects are a group of wildlife that are often overlooked, despite the fact that they dominate every global ecosystem in terms of species richness, biomass, and ecological function, and are the foundation of many food chains. They play many roles including being pollinators, speeding up decay and returning nutrients to the systems that need them, controlling pest species (such as agricultural and garden pests), and being food sources for other fauna such as birds and mammals and even carnivorous plants. Despite their importance and abundance, information on them is limited; CVC does not yet have a list of common insects in the watershed. Profiles of several insects and insect groups are below.

Dragonflies and Damselflies – Odonata

Dragonflies and damselflies (aka odonates) are very important ecologically. As insect predators close to the bottom of the food chain, odonates reflect changes in the health of aquatic ecosystems much faster than can be recognized through monitoring of most other animal or plant groups. These “indicator species” can therefore provide a measure of the current health of aquatic ecosystems as well as predict future changes in those environments. In Ontario alone, there are over 160 species of odonates.

DragonflyDragonflies are fairly fat-bodied and hold their wings flat when they are at rest. Their front wings are a different shape than their back wings and they can fly quickly and directly. There are several different groups of dragonflies, often classified for their appearance.  For example, the spiketail dragonflies (Cordulegastridae) are large dragonflies that are usually confined to small clear creeks flowing through forested areas. They are dark with bright yellow markings on their thoraxes and abdomens. Females have a large spike-like projection coming off the end of their abdomen that they use for spearing their eggs into the mud.

DamselflyDamselflies are smaller than dragonflies, are very thin-bodied, hold their wings above their bodies when at rest, have similarly-shaped front and back wings, and tend to fly weakly. The Broad-winged damselflies (Calopterygidae) are Ontario’s largest and most colourful damselflies. There are two groups of broad-winged damselflies, and both are river-dwellers with colourful wings. The jewelwings (Calopteryx) have black pigments on their wings and iridescent bodies. The rubyspots (Heterina) are similar, but have bright pink at the bases of their wings.

Monarch butterfly – Danaus plexippus

Monarch ButterflyMonarchs migrate thousands of kilometers from their breeding grounds in Ontario to their winter home in Mexico. In the summer and early fall, individuals can be seen flitting from flower to flower dining on nectar. In mid-fall, they can been seen in huge numbers near the shores of Lake Erie and Lake Ontario, where they cluster together on trees to form overnight roosts before crossing the lakes. These roosts may contain a few hundred to several thousand individuals. Monarchs typically form clusters in the same areas year after year.

Monarch populations do fluctuate regularly as a result of winter storm mortality, poor breeding conditions, predation, and other pressures. However, they are now suffering consistently high levels of mortality. There is concern that the monarch population could be reduced to a level too low to sustain itself. As a result, the monarch butterfly is identified as a species of Special Concern, by both the provincial and federal governments. This means that the species may be at risk of becoming threatened or endangered if steps are not taken to safeguard its survival.

In Mexico, human alteration of the monarch’s habitat, particularly the opening of forests by logging, has increased the negative effects of winter storms and has made the overwintering monarchs more susceptible to predation. In the past, these declines have been counterbalanced by the increase in breeding habitat in eastern North America. However, increased development throughout North America, as well as herbicide use around fields, may result in dwindling numbers due to the eradication of nectar sources and breeding habitat. Monarch caterpillars are also in a potentially precarious position since they feed exclusively on one type of plant – milkweed.

Hover flies – Syrphidae

Hover flyHover flies or syrphid flies (Syrphidae) are a good example of an overlooked but important and interesting group of insects. These are small to medium-sized flies, with short, stubby antennae and big compound “eyes”. These “eyes” are actually made up of hundreds of small “eyes” called ommatidia. Hover flies often have markings or colouring that resembles wasps and bees, leading some to give them the title “wanna-bees”. For example, one hover fly (Eristalis tenax) is called a “drone fly” as it often is mistaken for a honeybee drone.

These flies can most often be seen hovering in mid-air, and then either darting forward quickly, or landing on flowers where they then feed on nectar and pollen. Because of their feeding activities they help to pollinate flowers – a role that some people assume belongs only to bees. Their larvae resemble legless caterpillars and some species (e.g. Toxomerus marginatus) can be found on foliage eating various herbivorous insects. One little larva can eat up to 400 aphids during its development. So not only are the adults important pollinators, but their larvae are good at pest-control, which makes these hover flies a great addition to your garden.

Bumble bees –  Bombus spp.

Bumble beeBumble bees are perhaps the most recognizable type of bee: big, hairy, often yellow or black in colour, and very common. They are a social bee, meaning that many individuals all work together in one nest for the greater good of the colony. However, unlike the social honeybee, bumble bee colonies do not overwinter.

A queen bumble bee starts off in the spring all by herself, and so she must find a suitable place to start a family or colony in. For example, abandoned rodent holes and areas of thatchy grass/vegetation are a preferred place to call “home”. After finding a suitable nest, she starts laying eggs. She then flies from flower to flower collecting pollen and nectar to store in the nest. This is the food for her first generation of offspring. Once her daughters grow up and become adults, she stays inside the colony laying eggs while they go out, collect the food, and help raise their siblings.

In the fall, “sons” (male bees) are produced. They then mate with the youngest generation of daughters, which then seek out a place to overwinter. Sadly, these males and the rest of the colony, including the original queen, die as fall progresses into winter. But in the spring, the new queens emerge and start the cycle over again.

Bumble bees are good pollinators because they are very hairy, which means that pollen can stick to them and be transferred from one flower to another, helping the flowers set fruits and seeds. As well, bumble bees start flying early in the spring, even when it is cold out, which makes them good pollinators of our spring-flowering plants.

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