“As an entomologist only you are crazy enough to look forward to a dangerous heat wave because you can take something positive out of it,” Wrote Insect researcher Thomas Hörren, 32, packed traps, a net and a lamp to take advantage of the special situation. why?
Globalism: Where did you go to collect beetles and watch them?
Thomas Horen: I’m south of Karlsruhe in a larger forest complex.
Globalism: And why in this heat?
Listen: Many insects avoid the heat in the summer and are not active during the day. Then they gather in the evening hours and into the night. The higher the temperature, the longer it will swarm. Temperature is a limiting factor: if the temperature drops, for example, to 16 degrees and there is dew, then nothing will fly anymore. On tropical nights with warmer air, very small organisms can fly.
Globalism: Does this apply to all types?
Listen: On these nights one finds mainly species of beetles that live in small standing bodies of water. They need these flights to find new water. Especially in summer there is a risk of dehydration.
Globalism: What is the cause of crowding?
Listen: In many species, these are pure mating flights. Some species even wait for hot summer days before they can gather. Many beetles actively migrate, sometimes hundreds of kilometers, opening new habitats. Especially at such high temperatures, one finds species that are absolutely not suitable for the habitat. They must have covered dozens of kilometers in one night.
Thomas Horn Lighthouse turns on a little before dawn
Source: Thomas Hörren
Globalism: How does that work with light?
Listen: The lighting system is powered by a 12-volt battery and uses light spectrums in the ultraviolet range. On the one hand, there are active light traps. Beetles fly on the window glass behind which UV light shines. They drop and end up in a sample. This can also be used to quantify, preserved in alcohol and evaluated in a laboratory. On the other hand, we use the “lighthouse”, which is a grid-like structure with a lamp in the middle. Animals land on the net and can be observed. You have a variety of colorful insects in the light, which are active very differently.
Globalism: what did you find?
Listen: If a glowing evening took place in such heat, then approximately 300 species of beetles could be detected. That’s a lot. You get insight into one evening that rarely works with other methods. Species of beetles that live underground and develop on fungi such as truffles appeared. For example, the horned dung beetle (Bolboceras armier) or truffle beetles of the genus Lloyd’s. They fly very briefly to reproduce and are rarely found in other ways.
Globalism: Are there temperature limits at which swarms stop?
Listen: we do not have. 40°C days and 30° nights are exceptions, even in the hottest southwest of Germany – also during the past decades. So one cannot say much. We only notice this increasing effect of crowds.
Globalism: What changes with increasing warming?
Listen: Some habitats suffer greatly from heat and extreme conditions. Small, temporary bodies of water hold much less water or no water at all for several years. Also alluvial water. The species has fewer habitats where they can reproduce. In the case of peatlands, they are now known to be more vulnerable to climate change. Alpine bugs also have a problem when they are in icy areas and need moisture and seasonal snow. These species are currently migrating upwards.
The flat-nosed wood weevil (Gasterocercus depressirostris) is a deadwood beetle that is sometimes detected by light.
Source: Thomas Hörren
Globalism: What about the majority?
Listen: With most insect species we have a trend: the warmer they are, the more interesting they are. Insects of open ground depend on a certain number of hours of sunshine. you benefit. We also have a north-south divide, and there are much fewer species in Schleswig-Holstein than in Baden-Württemberg. And in many areas, change is taking place.
Globalism: Are there species coming from the south?
Listen: yes. On the other hand, species migrate from the Mediterranean region. The warmest region is Kaiserstuhl, where almost every year a species not previously found in Germany appears, such as the strawberry beetle from South and Central America (Stelidota geminata). Southern species continue to migrate north, where the heat is dispersed, along the Rhine plain and into the major cities on the river. This has increased significantly as a result of the warm years.
Globalism: When you’re out at midnight, how do you feel about it?
Listen: I’m a bit tired. Hot nights are not easy to plan in advance, they interfere with regular work. I still find it very exciting. I spend most of the day cold in the office. Yesterday it lasted until three in the morning, so I sleep longer in the morning.
Globalism: What about mosquito bites?
Listen: I use a variety of sprays for short-term protection from mosquitoes, as I get bitten a lot and react aggressively. But that’s just a little help, on nights like these, I’m really freaked out by mosquitoes. But this is part of it.
for someone
Thomas Horen, 32, is an entomologist and colonic pathologist. He is a member of the Krefeld Entomological Society. There he was a co-author of a long-term insect study in 2017, which caused quite a stir around the world. as such dead Report his work.
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