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Friday, 16 July 2021

Chaser

Four-spotted Chaser (Libellula quadrimaculata) – immature male
Before we added the pond to the garden, most of the dragonflies we saw were fly-bys; we'd get quick views as they raked past over the flowerbeds in search of a meal before carrying on to somewhere else. Now, we regularly find them perched and resting, often on the various sticks and bamboo arches Mike has installed around the water's edge. This young male Four-spotted Chaser (Libellula quadrimaculata) spent a few days hanging around the garden late last month, and it (or another) has been seen sporadically since. Though similar in colouring to the female Broad-bodied Chaser (Libellula depressa), this one is much slimmer-bodied, and has distinctively a dark spot at the node halfway along the leading edge of each wing. It also has an amber patch at the base of each wing, while similar patches on the Broad-bodied Chaser's wings are black. As an adult, its body will darken to a deep brown. Females are somewhat broader-bodied, and gingery where this one is brown. Where his appendages (the claspers at the end of his abdomen, which he will use to hold onto a female during mating) are slightly splayed, hers would be straight or even slightly convergent. 

Like all dragonflies, the larvae of Four-spotted Chasers are aquatic, feeding on other insect larvae and small tadpoles. Still waters – like our pond – are preferred, particularly if they have plenty of vegetation. Adults feed mainly on midges, mosquitoes, and gnats, so we're happy they're around. This widespread species is common across the British Isles, as well as across temperate Eurasia and North America; it's actually the state insect of Alaska. Apparently, it used to undergo huge migrations in the past. It's typically most abundant in early summer, but flies from late April through September, so there's plenty of time to see more.

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