There is a group of darners that fills a special niche in the dragonfly world. These are the duskhawkers, a group of medium to large dragonflies with habits that set them apart from most other species. Although there are other dragonflies with somewhat similar habits, I speak of the members of the genera Gynacantha and Triacanthagyna.
They avoid the hot and sunny hours of the day, but fly for relative short periods in the evening, most commonly in, but not restricted to, the autumn and winter months. Some species occur when it is still relatively light, others when it is almost dark. During those restricted hours they hunt for small insect prey, mostly mosquitoes. During the day they hang inside the forest amongst tangles and vines, or clinging to tree stems, waiting for the feeding frenzy to start when the sun sets.
On cloudy days some species may fly about inside the forest, or even appear at the forest edge, but only at the appointed time do they venture into open areas. Some species patrol small areas just above the ground, flying in straight lines, like G. mexicana, or above small waters, like G. bifida. Others, like G. nervosa, fly in more irregular patterns.
These three species are the representatives of Gynacantha have so far been found in the lower foothills at REGUA and all three are appearing relatively late, with G. mexicana flying so late that it appears often as no more than a ghost, an ephemeral shape flitting in and out of reality. Meaning that you see it for an instant, but when you register seeing it, it has already disappeared into shade, only to reappear and disappear again and again while you try to follow its flight pattern. A wisp of smoke, a spirit, moving in complete silence a feet or so above the ground. High up, around 1000 masl, there is a fourth species, G. adela, that appears to fly earlier, or even in the middle of the day when there is cloud cover.
These large duskhawking darners are preceded by the members of the genus Triacanthagyna. These are somewhat smaller and occur in higher numbers, regularly swarming with a hundred or more over open spaces. One moment they are not flying and the next they cascade out of the forest into the open in the hour before darkness, to dance around, sometimes high in the sky, sometimes low over the fields, and to retreat suddenly at twilight, to be replaced by the members of Gynacantha.
Three species have been identified until now at REGUA. The larger T. caribbea is the first to appear, when it is still very light, soon joined by T. nympha, a species somewhat smaller, but very similar in general appearance, and later again by the often abundant T. septima. There may be other species in the area. The trouble is that duskhawkers are difficult to catch or observe, irrespective of their abundance, due to their crepuscular habits and often very erratic flight patterns. That is of course exactly why they are such an exciting group.