Sitemap is very important tool for your blog, it helps to index all your pages. You should realize that a search engine only indexes your home page, so if you updated your blog weekly or even daily seems it just nothing. Search engine cant indexes your new page that have individual post page. For this your blog badly needed a sitemap. Actually sitemap does not affect on your SEO but it takes effect on your blog traffic, you can loose lot visitors and you only create much page that useless. Yes your new page does not indexed by search engine.
By using sitemap your blog can get a lot traffic, you can’t underestimated how the importance of sitemap for your blog. By a sitemap all pages have a link to your home page. Your page with all submitting articles should be indexes and get ranked after you created your blog sitemap. As on Google crawling and indexing, sometime it spiders will miss your new pages. In this case the stand alone page without link from any other page that missed by Google spider. So you can relax if you write another article on your blog.
Why Blogspot? Blogspot is a familiar blog for free, and it is easy to use and manage it. But in blogger blogs you can’t add an XML sitemap, since you can’t upload file to blogger. For this you can use your Blogger Atom or RSS feed as your sitemap. After you sign into Google Webmaster you can go to your website profile and click Add under sitemap. Then choose the type of sitemap as General Web Sitemap. In the field provide, just complete your feed URL. If you used Feed Burner to burn your feed and have put it as your default feed in Blogger feed setting, then instead of feeds/posts/default use feed/posts/default?rss. From now on all your post will automatically indexed by search page.