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paul
@paulhansel.com
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paulhansel.com
Limax maximus, the leopard slug.
#slugs #slugsofamerica
A leopard slug curled into a ) shape on some wooden planks. It has two areas on its body: the head, which is spotted, and the tail, which is similar but a bit darker.
January 30, 2026 at 9:04 PM
paulhansel.com
Myrtillocactus geometrizans f. cristatus.
#cactus
Crested blue flame cactus. It has long, almost vertical, segmented leaves, with curled, hammer-like tips that look like flames.
January 28, 2026 at 11:46 PM
paulhansel.com
Re-sharing a thoughtful video from The Steady State:

xcancel.com/steadystate2025/status/2015163848483918244#m
January 28, 2026 at 6:00 PM
paulhansel.com
These organs also enable chemotaxis: motion towards sources of chemical emission.

By sensing CO2 and water vapor gradients in the air, ticks can hunt their prey: mice and other mammals, including humans.

But there's a weak spot. Microscopic amounts of DEET, an insecticide, fully confuse the organ!
Repellents abolish tick thermotaxis Because of the clear importance of thermotaxis in host-seeking, we ran thermotaxis trials with unfed virgin adult female A. americanum ticks in air containing DEET, picaridin, 2-undecanone, citronellal and nootkatone, to determine whether these commercial repellents disrupted thermotaxis. Scoring final position after 5 minutes as a choice assay, 50 ng•cm-3 DEET, 54 ng•cm-3 picaridin and 42 ng•cm-3 2-undecanone completely abolished thermotaxis, and the effect was completely reversible within 15 minutes (Fig 7, S3 Fig and S1 Movie). Thermotaxis was also disrupted by citronellal and nootkatone, but because of the difficulty in removing the odor of these compounds from the arena, only the highest concentration of each compound was tested, with only eight and 24 ticks, respectively (Fig 7B).
January 28, 2026 at 4:28 AM
paulhansel.com
Did you know? Ticks have sensing organs on their front arms that work just like ranged infrared thermometers.

Ticks use them to sense warm bodies as far away as 4 meters, or 13 feet!

Hungry ticks run towards targets between 37-40C—human body temperature—and mostly ignore hotter and colder targets.
A hungry adult deer tick captured in an RMS lens tube. It is the size of a sesame seed. Quote from paper: the remainder, 31, were thermotaxing. Since 31 of the 43 ticks that were not moving spontaneously, or 72%, began thermotaxing immediately from 1m away, we can conclude that at least 72% of adult A. americanum females can detect the 10X10 cm plate at a distance of 1m, just as many as a t 0.5 m. A longer arena or smaller target is needed to precisely assess the range of tick heat detection, but we can conclude that since an adult human torso is approximately 4 times the width of our target, a tick could detect an adult human at a distance of up to 4 meters under ideal conditions. A cartoon of the test arena used to evaluate thermotaxis and chemotaxis in ticks. There are hot and cold plates on the left and right sides and a circulation fan that pulls air from the edges near the targets and blows it out at the center. Various data plots showing thermotaxis (movement towards heat sources) by ticks in a laboratory test. The ticks prefer walking towards hot plates around human body temperature (37-39C).
January 28, 2026 at 4:28 AM