Does iOS send HTTPS requests through the HTTP proxy?

I am trying to write up an HTTP proxy server in node.js, and I have successfully managed to route unsecure HTTP connections through it. But when applications (on my iOS device) use HTTPS for APIs 'n such, it always throws an error, and the attempted HTTPS connection never hits the server. So there are a few explanations of what could possibly be happening:

• iOS chooses not to send HTTPS connections over the proxy for security reasons
• iOS is looking for an HTTPS connection at the server on a different port, but can't find one

Basically what I am asking is: What does iOS do with HTTPS connections when an HTTP proxy is configured?

Please ask for any details or further questions in the comments. Thanks.