When reading the story, you know that the code has been created by humans, so it might actually be english and use concepts like our number system, our computer code system (I'm thinking ASCII), things that you should not assume when decoding a real alien message.
Looking at the numbers I notice that digits 6 to 9 do not occur in the message, which is statistically unexpected. This leads me to believe the number base might be 6 rather than our common base 10. In the story there are insects mentioned. Insects have 6 legs, so this makes sense (after all, our base 10 was based on the number of fingers).
Next, I notice the code 052 appearing regularly, so that could be a space. Let's check a hypothesis. 052 in base 6 is 5*6+2 = 32. 32 is the ASCII code for a space!!
Now, a decoding algorithm is ready to be devised:
"for each number in the sequence, parse it as a base-6 number and then print out its corresponding ASCII value".
The following node.js snippet does this:
var code = ['220','241','255','245','052','313',
'311','052','312','303','052','312',
'252','245','052','205','241','251',
'253','243','052','203','253','302',
'251','244','303','301','053'];
var msg = "";
for (let n of code) {
msg += String.fromCharCode(parseInt(n,6));
}
console.log(msg);
And the message is.........:
Take us to the Magic Kingdom!
So, do these aliens want to visit Disneyland????