Scrapy: `start_requests()` and `start_urls`

I am using Scrapy 1.1, my question is:

After using start_requests() to make urls,start_urls is also necessary?
Can I delete it?

For example：

class demoSpider(RedisSpider):
    name = "demospider"

    redis_key = 'demospider:start_urls'
    start_urls = ['http://www.example.com']

    def start_requests(self):
        pages=[]
        for i in range(1,10):
            url='http://www.example.com/?page=%s'%i
            page=scrapy.Request(url)
            pages.append(page)
        retu pages