Dragonflies come in a stunning array of colors, from metallic greens and blues to fiery reds and sunny yellows. But does color indicate different dragonfly species, or can dragonflies of the same species have different color variations? Let’s take a closer look at dragonfly coloration to find out.
Dragonfly Coloration Basics
Dragonflies have four wings that are characterized by a complex venation pattern of veins. Their wings come in different colors and patterns depending on the species. Within a species, mature male and female dragonflies often display different color patterns. Immature dragonflies tend to have duller coloration before reaching full maturity.
The main colors seen in dragonflies are red, yellow, green, brown, and blue. Metallic and iridescent colors are also common, created by structural components in the wings. The wings may appear one color when viewed from above, and another color when viewed from below. Some species also display striking patterns of spots, bands, or stripes on their wings.
What Causes the Color Variation?
The specific colors and patterns seen in dragonfly wings are created by pigmentation and structural components:
– Pigments: Dragonflies have pigment cells called chromatophores that contain colored pigments like melanins, pteridines, ommochromes, and carotenoids. The type and amount of pigment in the cells determines the color.
– Structural components: Tiny structures on the wing surfaces, like ridges or laminar plates, can refract light to produce iridescent and metallic colors through optical interference.
– Pruitt’s Rule: This rule states that red dragonflies tend to inhabit drier, open habitats, while green and brown dragonflies prefer wet, forested habitats. The colored backgrounds provide camouflage.
Do Colors Indicate Different Species?
In general, yes – the species of dragonfly can often be identified by its characteristic wing coloration and pattern. But there are some exceptions:
– Some species show seasonal color variations. Individuals emerging early in spring may be less vividly colored than those emerging later in summer.
– Maturation brings color changes as individuals reach reproductive age. Immature males and females often look similar until maturity is reached.
– Temperature during development can affect pigmentation. Cooler temperatures may result in less vibrant colors.
– Rare color morphs can occur within a species due to genetic mutations. An unusual red male morph is sometimes seen in forktails.
So in most cases, major color differences do indicate distinct species. But minor variations can occur within a species due to stage of maturation, season, temperature, and rare genetic mutations. Taxonomic experts use subtle clues like wing venation, markings, and body structure to positively identify species.
Examples of Dragonfly Species and Color Variants
Here are some examples of common dragonfly species and their characteristic colors:
| Species | Common Colors |
|---|---|
| Green darner | Green thorax, blue abdomen |
| Blue dasher | Pale green thorax, blue abdomen |
| Eastern pondhawk | Green thorax, red abdomen |
| Widow skimmer | Black thorax with white bands, dark abdomen with yellow bands |
| Common whitetail | White thorax with black bands, white abdomen |
Some color variants that can been seen:
– Common whitetails: Rare yellow morph females occur
– Widow skimmers: Some males have darker abdomens
– Eastern pondhawks: Uncommon red thorax morphs exist
These examples show that while color generally indicates species, some color variants can occur within a species population. Subtle structural differences confirm the actual species identification.
Male vs Female Color Differences
In most dragonfly species, mature males and females display distinct color patterns:
– Males tend to have brighter, more vibrant colors and striking patterns. This is likely to attract females and display dominance to other males.
– Females usually have more subdued, camouflaged coloration. Their muted colors help avoid predator attention when ovipositing and hiding in vegetation.
– In some species, immature males resemble females until they reach maturity and develop adult male coloration.
For example, male emerald dragonflies have a bright green thorax and abdomen with a dark brown patch on each wing. Females have a brownish thorax and abdomen with small yellowish patches on each wing.
The different male and female coloration allows the sexes to be easily distinguished in most species, especially when coupled with structural body differences. This sexual dimorphism in color develops at sexual maturity.
Do Colors Change Over a Lifetime?
Dragonfly colors and patterns can change over an individual’s lifetime as they progress through different development stages:
– Eggs: Eggs are very small and generally white or pale gray, camouflaged against vegetation and substrate.
– Nymphs: Nymphs are the immature, aquatic phase. They are dull brown, grey, or green for camouflage. Some develop pale wing pads in later instars.
– Tenerals: Tenerals are newly emerged adults before full maturity. Colors are pale and washed out. Wings may appear frosted or cloudy.
– Immature adults: Colors darken within a few days of emergence but may still lack fully vibrant hues. Some species show little color difference between immature males and females.
– Mature adults: Full vivid colors and species-specific patterns develop within 5-10 days after emergence. Sexual dimorphism in color is apparent.
So dragonflies don’t hatch with their colors – the vivid hues develop gradually after emergence as sexual maturity is reached. Individuals may go through a series of color changes over their 2-6 week adult lifespan.
Why Do Dragonfly Colors Differ by Species?
There are several hypotheses for why dragonfly colors and patterns vary substantially between different species:
– Species recognition: Bright distinct colors may help dragonflies identify potential mates of the same species during mating swarms.
– Territory defense: Species-specific colors could aid males in defending territories from competitors. Intimidating colors may establish dominance.
– Predator avoidance: Some color patterns, like stripes, may help dragonflies evade predators or startle them.
– Thermoregulation: Darker colored dragonflies may warm faster in cool climates. Lighter colors may reflect heat in hotter regions.
– Environmental adaptation: Habitat-specific colors provide camouflage against certain backgrounds, improving hunting success and avoiding detection.
– Sexual selection: Females may preferentially select males with the brightest colors, driving the evolution of dramatic color differences between species over time.
Researchers continue to study the complex factors that drive the amazing color diversification across dragonfly species worldwide. There are likely multiple selective pressures and functions influencing the stunning coloration.
Dragonfly Color Variants Due to Temperature
Interestingly, ambient temperature during larval development can affect adult dragonfly colors. Individuals that develop in cooler water temperatures often emerge with less vibrant coloration:
– Cooler water slows larval growth, potentially reducing production of bright pigments.
– Cooler temperatures may limit activity, reducing pigment deposition into developing wings.
– Slower larval metabolism in the cold may affect aspects of pigment synthesis pathways.
– Changing temperatures could impact microbial symbionts that may contribute to pigment production.
– Colder climates may favor selection of less vibrant colors for solar heat absorption.
For example, some research on emeralds found that individuals reared at 64°F vs 82°F showed significantly less vivid green thoracic coloration. So cooler developmental temperatures can result in duller adult coloration in some species.
Conclusion
Dragonflies exhibit tremendous species-specific diversity in wing coloration and patterning. While color generally indicates distinct species, some color variants can occur within a population due to:
– Seasonal shifts
– Maturation changes
– Rare genetic mutations
– Developmental temperatures
Experts use structural features and markings to definitively differentiate species. But major color differences often reflect underlying species-level distinctions. Subtle environmental tweaks during development can sometimes create color variability within a species. So color alone doesn’t always denote a new species – but it provides a useful starting point for identifying dragonflies in the field.
