Since our study mimicked natural temperature conditions, we suggest that the increase in temperature variation predicted by climate models will not necessarily differ from the effects without an increase in variation.Ĭlimate change is mostly associated with increasing global temperatures, but larger temperature fluctuations are also predicted 1. Hence, positive and negative effects of temperature variation within the linear range of a species thermal performance curve might cancel each other out. There was neither a difference among the temperature variation treatments, nor between the constant and the variation treatments in growth and cannibalism. Cannibalism was significantly positively correlated with initial body size variance. Larvae were also raised at five constant temperatures for an estimation of the thermal performance curve, which showed that the thermal optimum for growth was 26.9 ☌. The temperature treatments included three amplitudes between 20 and 26 ☌ with an average of 23 ☌, and a constant control at 23 ☌. In a laboratory experiment we investigated the effects of thermal variation on growth and cannibalism in larvae of a damselfly. Understanding the temperature-dependence of competition is important since it might affect dynamics within and between populations. Little attention has been paid to the effects of thermal variation on competition within species. The Earth’s climate is changing with a trend towards higher mean temperatures and increased temperature fluctuations. I have a video of a male blue dasher dragonfly too, dated. I knew that male dragonflies were territorial, but perhaps females have the same concepts in their heads regarding to hunting rights and territory. They don't do things in a randomized fashion. One thing I noticed about dragonflies is that they keep returning to the same perch to survey their territory. It took me a long time to identify this as a female blue dasher dragonfly (Pachydiplax longipennis), but based on the photos on various peoples' pages online it seems like the phenotypes can vary quite a bit for at least this species. It's not as conspicuous as the male flame skimmer dragonfly I posted a video of before, but the blue dasher is beautiful in its own right when you look at it for a few minutes up close. This is one of the more common dragonflies I've seen in San Diego county, although they generally dart around so fast I can't see the level of detail that I can with my camera at 14x optical zoom. I saw this dragonfly in the riparian habitat of Los Penasquitos Canyon Preserve. Mosquitoes, flies, butterflies, moths, mayflies, and other soft-bodied flying insects. When they mature the adults emerge from the water at night.Īquatic insect larvae and freshwater shrimp After the eggs hatch the young (naiads) live in submerged vegetation. ![]() While doing this, the male hovers nearby, standing guard. Males joust over water by flying under an opponent and rising, forcing the opponent away from the water surface.Īfter mating the females deposits eggs by flying close to the water surface and dipping the tip of her abdomen into water. They perch on erect, slender plant stems. Lakes, ponds, slow streams, ditches, and possibly bogs Females sometimes develop pruinescence but much more slowly.Įastern pondhawk (Erythemis simplicicollis) male develops pruinescence on the thorax as well as the abdomen. It usually takes about 9 days for the pruinescence to develop. Immature males have reddish-brown eyes and a brownish-black abdomen which becomes increasingly prunose as it matures. The forewings are slightly narrower than the hindwings. They sometimes develop an uneven brownish-yellow tint. The wings are clear except for an amber patch at the base and a long dark stigma. They are blue or green in males, reddish-brown in females. ![]() The compound eyes meet along a long margin at the top of the head. The top of the upper part of the face (frons) is metallic blue. Segment 9 is unmarked and segment 10 is pale. On abdominal segments 3 through 8 there is a pair of thin yellow dorsal stripes. The female abdomen is much shorter, parallel-sided, and brownish-black. The abdomen of the mature male is tapered and powdery blue (prunose) with a black tip. The sides of the thorax are greenish-yellow with three dark brown stripes. There is a thin, pale, central (middorsal) stripe and two wider shoulder stripes. ![]() The upper (dorsal) surface of the thorax is brown with greenish-yellow markings. Blue dasher is a widespread, fairly common, small to medium-sized, 1 ⅛ ″ to 1 ¾ ″ long skimmer.
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