At the urban birds conference, there was also a lecture about insects.
It was by Kars Veling, about Butterflies and dragonflies in cities: more than food for birds.
There are quite some butterfly species in Dutch cities and towns. For one category of butterflies, that is not surprising. These are the species who are not so selective about environments. Caterpillars of species like red admiral, peacock, and small tortoiseshell are dependent on stinging nettles, plants which grow even in city centres.
With some luck, one may also see more selective butterfly species in urban environments, like the comma, and meadow brown.
There are also some really specialized species in Dutch cities. As far as we know, the white-letter hairstreak in the Netherlands lives only in Heerlen city. The brown hairstreak numbers are going down in the countryside, but are stable in cities like Wageningen and Zwolle.
Kars Veling once saw 700 common blue butterflies in the ancient town Naarden. He had never seen so many together. Their caterpillars eat bird’s-foot trefoil, abundant in Naarden.
Essex skipper butterflies may also flourish in urban environments. Provided that lawns are not mown, destroying the eggs.
Brown argus butterflies also thrive in cities sometimes, especially on temporarily fallow land.
In an oak tree, there may be 50-70 butterfly or moth caterpillar species.
Plants which attract butterflies: here.
Dragonflies and damselflies in cities, like elsewhere, are dependent on clear water. In muddy water, their larvae will not be able to see far enough, and will die. If you want willow emerald damselflies in your city, you need trees as well as clear water: because the adults deposit their eggs in autumn in trees standing close to water. If the larvae hatch in spring, they drop straight into the water. So, don’t cut down all trees near the water. But also don’t let big trees grow all along the water, for then the water becomes too shady. Try to find a balance.
What’s a city-dweller to do — you want to help fight climate change, but does planting trees in the city really make a difference? Can urban forests help sequester carbon and offset emissions? Here.
Panolis flammea moths in the Netherlands: here.
Conistra ligula moths in the Netherlands: here.
Insects of Oldenaller estate in the Netherlands: here.
Mauve bluet (Proischnura polychromaticum) damselfly: here.
August 2010: The nationally rare brown hairstreak butterfly appears to be making a comeback in Worcestershire, after being spotted in fields next to land recently bought by the county’s wildlife trust: here.
Amphibious caterpillars discovered in Hawaii
Scientists aren’t sure how the 12 species spend weeks underwater without breaking the surface. They don’t have gills and they don’t hold their breath.
Scientists have discovered 12 species of caterpillars that can survive for weeks underwater without ever breaking the surface. They don’t have gills and they don’t hold their breath. (University of Hawaii)
By Amina Khan
March 23, 2010
Moths of the Hawaiian genus Hyposmocoma are an oddball crowd: One of the species’ caterpillars attacks and eats tree snails. Now researchers have described at least a dozen different species that live underwater for several weeks at a time.
“I couldn’t believe it,” said study coauthor Daniel Rubinoff, an evolutionary biologist at the University of Hawaii at Honolulu, of the first time he spotted a submerged caterpillar. “I assumed initially they were terrestrial caterpillars . . . how were they holding their breath?”
Each of the 12 species lives in and along streams running down the mountains on several different islands of Hawaii, said Rubinoff, who has studied Hyposmocoma, a group of more than 350 moth species, for more than seven years.
They usually eat algae or lichen, and build silk cases — which one species even adorns with bird feathers — for shelter and camouflage. They spin silk drag lines to withstand the high pressure of fast floodwaters.
Unlike other amphibious creatures that can survive underwater on stored oxygen but must come back up for air, these caterpillars can spend several weeks without ever breaking the surface, according to the paper, which was published online on Monday in Proceedings of the National Academy of Sciences.
It isn’t yet clear how the insects do it. Rubinoff and co-worker Patrick Schmitz of the University of Hawaii did not find any water-blocking stopper over the caterpillars’ tracheae or evidence of gills. The animals drowned quickly when kept in standing water, so they seem to need the higher levels of oxygen present in running water, and probably absorb it directly through pores in their body, the scientists said.
The trait appears to have evolved more than once, Rubinoff said. After analyzing the DNA of the 12 amphibious species, the scientists found that three separate lineages of moth had developed the ability to breathe underwater at different points in the past.
Why they evolved this trick isn’t clear, but animals and plants are known to often evolve in surprising directions after arriving at new, sparsely populated habitats such as islands, said Felix A.H. Sperling, an entomologist with the University of Alberta in Edmonton.
In a new environment, released of the pressure of having to fight for food sources or evade predators, they are freer to expand into new niches.
“When the pressures on an environment are released, what crazy things are animals capable of doing?” said John W. Brown, a research entomologist with the U.S. Department of Agriculture.
“You just wonder . . . do all animals have that potential?”
Copyright © 2010, The Los Angeles Times
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