Thanks for the question.

We believe that these are larvae of the Three-Lined Potato Beetle (Lema daturaphila). This is what the adults look like:

https://bugguide.net/node/view/20935

The larvae look like this. Compare to what is on your tomatillo:

https://bugguide.net/node/view/653116

The one bright spot is that these beetles generally do not cause significant damage to the plant other than cosmetic appearance. Fruit production usually is not impaired. See the following for further information including management procedures:

https://extension.sdstate.edu/three-lined-potato-beetles-are-eating-my-tomatillos - :~:text=Larvae,-Figure 3.&text=The larvae are a shiny,much easier to spot them.

https://extension.unh.edu/resource/three-lined-potato-beetle-fact-sheet-0

https://www.insectidentification.org/insect-description.php?identification=Three-Lined-Potato-Beetle - :~:text=The multicolored Three-lined Potato,making them a garden pest.&text=This larvae of the Three,used to make salsa verde.

https://extension.umn.edu/yard-and-garden-insects/threelined-potato-beetles - :~:text=Threelined potato beetles are usually,esfenvalerate to reduce their numbers.

Good luck; please get back to us with any questions.