Taxes on 2 week pay checks.

[steelcmg]

So i got switched from a temp agency to full time with the company i work for. They have 2 week pay checks. I started in the middle of a pay periord and my pay check was about 500$. But then i just got payed again today and it was only 930$. That doesnt make any sence to me shouldnt my pay check be almost 1000$. I worked the same amount of hours 40 each week. I dont think they should tax more because the pay cycle is every 2 weeks compared to 1 week or do they?
If thats the case that complete bullshit because thats like losing 120$ a month because the company pays u every 2 weeks. This is the first time i have been on a 2 week cycle so i dont know how it works. Anyone out there have an idea why my check would do this.