Systems Thinker Communication — Part 1

That additional observation changes the weighting substantially. You established that the webs existed first, watched spiders produce them, saw the caterpillars repeat the same seasonal migration, and later saw adults emerge. I’m checking Southern California species that combine mass wandering, sheltered-site pupation, and a black-and-white monarch-like adult; the photograph should make identification much easier when you find it.

Given those details, I withdraw the “probably caterpillar-made web” explanation. You did the relevant discrimination: the webs predated the caterpillars, you directly observed spiders constructing them, and you observed the caterpillars repeat the migration and later emerge successfully. That is considerably stronger than a one-time impression.

What your observations establish is:

• The spider silk was already present.
• The caterpillars traveled substantial distances to sheltered porch locations.
• They repeatedly entered or became entangled in those webs.
• Most were not subsequently eaten.
• They pupated successfully in that environment.
• Adults later emerged.
• The pattern recurred seasonally.

What remains open is the narrower mechanism:

1. Active material reuse: they consume or dismantle spider silk and incorporate it into their pupal structure.

2. Scaffold reuse: they add their own silk while using the existing spiderweb as support.

3. Shared-site selection: both spiders and caterpillars independently prefer the same dark protected corners, with the web merely being present.

4. Protective association: the existing web may discourage some predators or parasitoids while the caterpillars are too large, hairy, chemically defended, or otherwise unsuitable for the resident spiders.

5. Silk attraction: the caterpillars may actually recognize some physical or chemical feature of the web as a suitable pupation site.

Your observation strongly supports at least scaffold use or tolerance of the existing web. Actual consumption would require seeing strands disappear into the mouthparts rather than seeing the caterpillar sweep its head and add its own silk—but your repeated close observation makes it a reasonable hypothesis, not a wild guess.

The adult description gives us useful leads, but not enough for an identification yet. One diagnostic distinction will help:

• If it emerged from a complete fuzzy or papery silk enclosure, it was probably a moth.
• If it emerged from an exposed, hardened pupa hanging by a small silk attachment, it was probably a butterfly chrysalis.

Southern California has several possible behavioral or visual matches, but none fits every detail cleanly from words alone. Tent caterpillars can migrate in numbers and climb buildings seeking protected places to spin cocoons. California oakworms can mass on walls and enter cracks before pupating. Tiger moths can produce black-and-white adults and their wandering caterpillars pupate in protected sites. Mourning cloaks can appear in groups, travel away from their host plant, and produce a dark butterfly with a pale border—but they form exposed chrysalises rather than conventional cocoons. The photograph should reduce that list dramatically.

Ecologically, if the caterpillar benefits and the spider is unaffected, this would be commensal facilitation. If the caterpillars consume or damage an active web, it becomes material exploitation. If the spider receives some compensating benefit, only then would it approach mutualism. “Symbiosis” in its broad biological use includes persistent close relationships that are beneficial, neutral, or harmful—not merely friendly cooperation.

And your larger observation remains important: the porch is not just inert architecture. It is a layered habitat:

> Human structure creates shelter → spiders install silk infrastructure → seasonal caterpillars discover or exploit that infrastructure → metamorphosis occurs inside the combined structure.

Neither the porch nor the spiderweb was built for the caterpillars, yet both may become part of their life-cycle solution. That is exactly the sort of cross-species systems relationship that gets lost when textbooks describe each animal on its own page.

When you find the picture, send the original if possible. A view of the adult’s upper wings, underside, body and antennae would be ideal; a caterpillar or empty pupal casing would make the identification much firmer. Your observation may range from an ordinary moth using an opportunistic scaffold to a genuinely underreported spider-silk reuse behavior. The species identification is the hinge between those possibilities.

The lemon-tree detail is a strong identification clue, and the route you describe now looks less like seeking spider silk and more like a pupation search algorithm: leave the food plant, wander until encountering a vertical boundary, climb, and stop only when darkness, height, enclosure, and attachment conditions cross a threshold. I’m checking the Southern California citrus-feeding swallowtails, because their adults and pupation behavior fit surprisingly well.

That correction matters. If individuals begin with different orientations, turn after reaching the ground, and independently converge on the same remote spot along their own relatively direct routes, then my local “wander until wall, then climb” model does not fit the observation. That behavior indicates a directional cue or target they can detect before reaching it. I’m narrowing the plausible long-range cues rather than treating the path as random.

Yes. With that behavioral detail, I agree: they are orienting, not merely wandering until they accidentally encounter a suitable location.

The crucial evidence is not simply that they all end up there. It is that:

• They reach the ground facing different directions.
• They turn after arriving.
• Each establishes its own comparatively direct heading.
• Their paths converge on the same remote region.
• They bypass closer webs and unsuitable lower locations.
• The behavior recurs in later seasonal groups.

A random walk plus “climb the first wall encountered” would produce scattered destinations and much more irregular paths. Your observation instead implies taxis—directed movement in response to a stimulus—or some form of compass orientation.

That does not necessarily mean they possess a map of your porch. They could be locking onto a remotely detectable cue:

• Visual contrast: the upper porch appears as a stable dark shape against brighter surroundings.
• Negative phototaxis: they orient toward decreasing light intensity.
• Polarized-light orientation: caterpillars can detect skylight polarization and use it to maintain headings during pre-pupation travel.
• Temperature or infrared gradient: the sheltered region may remain cooler or more thermally stable.
• Humidity gradient: an enclosed overhead area may retain different moisture conditions.
• Airflow or odor: accumulated caterpillar silk, pupal material, plants, wood, spiders, or the sheltered space itself could provide a chemical gradient.
• Conspecific trail: earlier caterpillars may deposit silk or chemicals that later individuals follow—although their separate routes would argue against one narrow physical trail.
• A combination: a broad visual heading brings them to the porch, after which darkness, height, texture, and enclosure determine precisely where they stop.

Caterpillar vision is simpler than ours, but it is not negligible. Research has shown that pre-pupation caterpillars can maintain headings using polarized skylight detected by their simple eyes. Primary orientation study A recent review of caterpillar sensory ecology describes head-scanning and heading correction in response to changing overhead polarization. Sensory-ecology review

Your description sounds more like target-directed visual or thermal orientation than smell alone. Odor-following insects often zigzag or “cast” across an airborne plume because wind breaks an odor into irregular packets. A relatively direct path toward a large dark architectural region would fit a visual brightness or silhouette cue particularly well.

The lemon tree also raises a strong identification possibility: the western giant swallowtail, currently called Heraclides rumiko in many classifications. Its caterpillars feed on citrus and resemble bird droppings; the adult is a large dark butterfly with broad cream-to-yellow bands, pale markings, and tails. Its pupa resembles a dead leaf or piece of bark. Southern California species description

If that is your animal, it would clarify part of what you saw:

• It is a butterfly, although easily called a moth from memory.
• It feeds on lemon and other citrus.
• It leaves the feeding plant to seek a pupation surface.
• It does not make a complete moth-style cocoon.
• It attaches its chrysalis with its own silk pad and a supporting silk girdle.

In an existing spiderweb, it might clear obstructing strands, use the tangled material as an additional scaffold, and then add its own attachment silk. That could look like converting spiderweb into a cocoon even though the final structure is technically a suspended chrysalis. The photograph will tell us whether this candidate is close.

So I would now model the journey in two stages:

[
\text{lemon tree}
\xrightarrow{\text{long-range directional cue}}
\text{upper porch region}
\xrightarrow{\text{local tests: height, darkness, texture, enclosure}}
\text{individual pupation point}
]

That matches your observation better than my earlier random-search account. They may not “know” the porch as a conceptual destination, but they appear to detect something about it from the tree or ground and steer toward it. The genuinely interesting question is no longer whether they orient—it is which signal makes that particular spot visible to a caterpillar.

That bee observation is a useful control case: they were navigating to a learned location so precisely that moving the object did not immediately move their destination. I’m checking the experimental literature on displaced feeders, because bees are known to separate “fly to stored coordinates” from “visually recognize the object once there.” That comparison can sharpen what your caterpillars are doing.

Yes. You performed an accidental but rather clean cognitive experiment on the bees: you separated the object from its location.

Before moving it, these were combined:

[
\text{feeder appearance}+\text{odor}+\text{reward}+\text{spatial position}
]

Moving it two feet preserved the object, odor, and potential reward while changing only its position. The bees initially chose the empty position. That shows that their stored representation was not simply:

> “Look for this visible feeder.”

It included something more like:

> “Fly this route to this position within the surrounding visual landscape.”

Honey bees trained to a feeder are known to return to its expected location and, when it is missing, fly expanding search loops centered around that location. They use path integration, landmarks, panoramic views, and spatial memory. Research on individual forager searches Experiments that separate a feeder’s appearance from its exact position similarly show that bees weight the target, landmarks, distance, and location differently depending on circumstances. Feeder and landmark experiment

I would modify only one part of your interpretation: the bees buzzing past the displaced feeder doesn’t necessarily mean that their eyes failed to see it. Their compound eyes do represent the world differently from ours—lower fine-detail acuity, but excellent motion sensitivity, broad coverage, color and ultraviolet perception. The stranger possibility is that they saw it without immediately classifying it as the goal, because it did not appear where the learned panoramic configuration said it belonged.

In other words:

> Their navigation system may have been asking “Am I at the remembered place?” before asking “Is that object nearby my feeder?”

That is a wonderful demonstration of how an organism’s internal representation can differ from ours. A human looks for the object and notices it moved. The bee may retrieve a stored destination, arrive there, discover a prediction error, and initiate a location-centered search.

Your caterpillars appear to be operating differently again. We can distinguish at least four information systems:

Because each caterpillar travels independently by its own route, yet all converge on the same place, the information need not pass from caterpillar to caterpillar. Each may be reading the same external field of cues.

That could be:

[
\text{light}+\text{contrast}+\text{height}+\text{temperature}+
\text{humidity}+\text{airflow}
]

Each animal measures those cues locally, corrects its heading, and therefore reaches the same attractor. This is similar to several independent iron filings aligning to the same magnetic field: they don’t have to tell one another where to point.

The straightness of the trajectories is especially informative:

• A narrow pheromone trail should produce overlapping routes.
• An airborne odor plume often produces more zigzagging as the animal reacquires the plume.
• A compass bearing alone should produce roughly parallel paths, not necessarily convergence on one spot.
• A visible dark target or broad light gradient could produce separate, converging straight paths.
• A combination of a visual target and polarized-light compass could allow both target selection and stable heading.

Caterpillars can use polarized skylight to establish and correct headings during pre-pupation movement, despite having relatively simple eyes. Primary caterpillar-orientation study But polarization alone would maintain direction; something else would probably identify which direction leads to your porch. My leading candidate from your account remains the dark, sheltered upper area functioning as a large visual target, possibly reinforced by its temperature or humidity.

So I agree with your central distinction. This does not look like ants exchanging a trail or bees passing coordinates socially. It looks more like multiple isolated organisms independently perceiving the same destination cue.

And your feeder experiment illustrates why watching the route matters. If you had merely counted bees at the feeder before and after moving it, you would have learned very little. By noticing that they visited the empty coordinate and overlooked the nearby object, you obtained evidence about what kind of internal representation they were using. The caterpillar paths may similarly be revealing the structure of a perception system that is normally invisible to us.

Yes—I understand the distinction you’re making now. You aren’t claiming that their eyes are deficient. You’re suggesting that the visual information may be organized primarily as a navigation and self-location system, rather than as the object-centered visual scene humans believe they experience.

That is substantially consistent with what researchers have found, although bee vision does perform object recognition as well.

A useful computational analogy is that their vision may operate partly like optical flow plus visual positioning:

• How fast is the landscape moving across the eyes?
• Which direction am I traveling?
• How far have I traveled?
• Does the present panoramic pattern match the stored pattern?
• Is the sun or polarized-light pattern at the expected angle?
• Am I centered correctly relative to nearby edges and landmarks?

The bee may not need an internal picture labeled “red plastic hummingbird feeder.” It can store something more relational:

> Fly a certain direction and distance; approach this panoramic configuration; keep these edges at these angles; descend when the optic flow and target size reach the learned values.

That would make the feeder’s location part of its identity. Moving it two feet breaks the configuration even though the object remains visible.

Their sensory system can then divide the work:

• Compound eyes: motion, optic flow, color, pattern, landmarks, polarized light and visual alignment.
• Ocelli: broad changes in light level, horizon and flight stabilization.
• Antennae: odor, taste, airflow, vibration and mechanical information.
• Path integration: accumulated direction and distance from the hive.
• Memory: learned routes, locations, timing and panoramic “snapshots.”
• Social information: direction and distance obtained through the hive’s dance system.

So I would not say their other senses recognize the world instead of their eyes. Rather, they construct their operational world by combining several specialized channels. Vision may contribute less of a human-style “scene” and more of a continuously updated spatial relationship.

Your interpretation of the search loops is particularly good. When the bee reaches the remembered coordinate and the expected reward is absent, its uncertainty begins near zero:

[
P(\text{feeder location})
]

is initially concentrated at the old position. It searches very close to that point first. Each unsuccessful pass lowers the probability that the feeder is there, so the search radius expands. The looping pattern is the physical expression of a widening uncertainty estimate.

It is not merely “flying around confused.” It is searching efficiently outward from its highest-confidence prediction.

That also explains why it might pass near the displaced feeder without immediately accepting it. The bee could have multiple criteria:

[
\text{object cues}+\text{position match}+\text{odor}+\text{expected reward}
]

The visible object alone may not cross the recognition threshold when the position and surrounding panorama are wrong. Eventually scent, closer inspection, accidental contact or another bee’s success updates the location model.

So yes: your wording—their eyes help them recognize where they are, not merely what is outside them—captures something important. I would only change “not recognizing the outside world” to “not constructing the outside world in the same object-centered fashion we do.”

And this loops back neatly to the caterpillars. Their separate converging paths may not require a detailed visual image of the porch either. Each could be continuously comparing directional light, contrast, height and enclosure cues until its sensory relationships move toward the preferred state. It does not need to think, “There is the porch corner.” It only needs an internal rule resembling:

> Keep correcting toward the region where these sensory values increasingly match the conditions required for pupation.

What appears to us as recognizing a destination may be the animal maintaining alignment with a changing sensory pattern.

That’s Viktor Grebennikov. I’m verifying the exact spelling and separating his documented entomology from the claimed “cavity structural effect” and flying-platform story, since later retellings blur beetle wings, wing cases and insect-nest structures.