Arthropods--the most ubiquitous and diverse animals on Earth.

remember, arthropods are an entire PHYLUM. It includes all animals that have several sets of paired legs, exoskeletons, and body segments. Each subphylum unit has sex and growth habits often unique to that class.(Like scorpions are oviviporous , giving birth to live young) and several classes have no"terminal" instar. Some marine chelicerae grew to be many feet acrosss, like theparacarcinosoma which were some of the earliest "sea scorpions" of the eurypterid clan. Fossils of these Ordovician mamas can be big a a collie dog with an extended "tail" with segments like a lobster.The end of the eurypterids came in the late Devonian with a mini mass extinction (they missed the Ordovician one). AT their terminal age, these guys were sometimes eight feet long and could have been a serious predator in the brackish water like shallow bays.

Insects , true spiders, mites, and millepedes seemed to make their appearance in the fossil record of the late Devonian when plants began to seriously claim the land and grow to tree size members.

Its been suggested that the phylum nematoda is perhaps even bigger than arthropoda. (Based on actual species AND pounds per cubic miles).
Whn J S Haldane was asked to give his feelings about a God, he said;'
"Im really not certain but He does seem to be inordinately fond of beetles" .

This is an interesting question about whether arthropods continue to grow after they reach sexual maturity. I know that with insects once they reach the adult mature stage they cease to grow, even with those undergoing incomplete metamorphosis. The nymphs undergo several molts, but once they reach their adult stage there's no more growth. With most spiders, the araneomorphs, at any rate, molting stops once they reach sexual maturity. At least some of the mygalomorphs, such as the tarantulas, continue to molt once they reach sexual maturity. That are so long-lived, with females living up to 30 years, that they have to molt to regenerate lost limbs. But I don't know if size increases with each molt. Even with tarantulas though, a maximum size is reached.

continued growth in arthropds that develop via ecdysis (molting exoskeletons) and, while still soft the exoskeleton swells from "pumping" body fluids throughthe animal. These kinds are limited to those that live in the water(I think I mentioned that already). Its a function of distribution of oxygen throughout the body.
Consider the ancient "Water scorpions" and existing water chelicerae, like lobsters or crabs.

This is a golden tortoise beetle in the family Chrysomelidae. I've only seen one of them in my life, in my backyard, and it was years ago. They're less than 1/2 inch long. The margin of the whole insect is transparent.

The transparent margin of this beetle is a shield or shell which covers the whole beetle. During copulation or any kind of a disturbance such as a person poking it, it has the ability to change the color of this shield. The color seems to mimic ladybird beetles, which are distasteful to birds, so the tortoise Beetle gains a of sort of protection with this Batesian mimicry.

Glad you ditched the anal fork, Golden Tortoise Beetle
By Becky Crew
https://blogs.scientificamerican.com/running-ponies/glad-you-ditched-the-anal-fork-golden-tortoise-beetle/

Here's one changed to mimic a ladybird beetle.

Here they are copulating with a color change.

Here's the larval stage. It piles up the larval shed skins from the previous instars and forms a sort of a camouflage.

Here's another insect in the habit of carrying trash on its back.

This is a green lacewing larva or aphid lion. It piles the spent cuticles or exoskeletons of it's a dinner victims on its back. Also, it collects little bits of lichen and other plant materials. As its name suggests aphid lions feed on aphids. But aphids are often tended by ants, who feed on the honeydew excreted by the aphids, and they're very protective of their charges. Any intruding aphid lions are quickly kicked off the plant or even killed. However, those with trash piled on their back are usually ignored by the ants.


Green lacewing larva or aphid lion. Notice the vicious pincers for penetrating aphids.


Green lacewing adult.

I did a couple of watercolors (rather large format) of some iridescent tropical beetles. I did these back in the 1990's , I dont recall doing a tortoise beetle but I had a pair of "mug shot paintings" of emerald ash borers which were just becoming a new problem in our area. Beautiful coloring, badass bug.

Here is another trash collector, this time a spider, the trashline spider, Cyclosa turbinata. I've seen a few of these and they're pretty easy to identify by the vertical line of trash in the orb web. The trash is composed of the discarded cuticles of its prey insects and maybe some egg cases.

In this picture the arrow points to the spider, but it's still very difficult to perceive, probably even more so to a passing bird. So it's possible that the trashline merely hides the spider, but it also may make the web more visible to birds so they don't go crashing through it destroying the web.





Even close up the spider is difficult to distinguish. It looks like the head is pointing down.

This is a trash-carrying or debris-carrying assassin bug. This one preys upon ants and it has loaded the ant cuticles on it's back. The cuticles are spent exoskeletons that are left after the insect has sucked the ants dry. This debris-carrying not only hides the insect to a certain extent, but also thwarts attacks from small predators such as other insects or spiders. The spiders have difficulty recognizing the assassin bugs as prey when they're covered by debris.

This is the adult of another species of assassin bug, the wheel bug. It has a rather forbidding appearance. Notice the long, penetrating proboscis arising from the front of the head.

Golden tortoise beetle

Golden tortoise beetle mimicking ladybird beetle.


Golden tortoise beetles copulating showing change of colors.

Underside of the beetle showing the shield.

Larva of golden tortoise beetle showing the debris piled up including its formerly shed cuticles, bits of lichen, and other plant debris.

Assassin bug nymph showing debris pile up on its back, mostly ant cuticles which are the exoskeletons.


Assassin bug adult. Notice the folded back proboscis which it uses to penetrate insects.