I don't know how they shipped them, but apparently you can ship some animals through the US Postal Service.

https://pe.usps.com/text/pub52/pub52c5_007.htm

Spiders and poisonous insects aren't allowed though, except scorpions under certain conditions.

I’ve ordered bees through the mail before; it’s quite a common way to get them actually.

But does that theory have legs...?

Use PreyPal!

Arachnid Prime?