Strange 404 Errors In Logs

Hi all - I've noticed recently I've been getting a lot of strange 404 errors in my logs. A few examples:

PHP Code:

404 Page Not Found: Apple-touch-iconpng/index
404 Page Not Found: Apple-touch-icon-precomposedpng/index
404 Page Not Found: 404javascriptjs/index
404 Page Not Found: 404testpage4525d2fdc/index
404 Page Not Found: Faviconico/index 


Some of them are things that exist (apple-touch-icon.png), but the 404 error has missing file extensions, and a "/index" after it. Some of them are files that don't even exist (404testpage4525d2fdc). I've run through the entire site looking for broken links, and there are none. I'm also not getting any 404 errors showing on the actual site - just in the logs.

My .htaccess file:

PHP Code:

RewriteEngine On
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule ^(.*)$ index.php?/$1 [L] 


And my routes file:

PHP Code:

$route['default_controller'] = 'welcome';
$route['404_override'] = '';
$route['translate_uri_dashes'] = FALSE;
$route[LOGIN_PAGE] = 'users/login';
$route['landlords'] = 'listings/directory/1';
$route['complexes'] = 'listings/directory/2';
$route['managers'] = 'listings/directory/3';
$route['apartments/sublets'] = 'listings/index/13';
$route['apartments/roommates/19'] = 'listings/index/19';
$route['apartments/roommates/20'] = 'listings/index/20';
$route['apartments/roommates/21'] = 'listings/index/21';
$route['apartments/roommates/22'] = 'listings/index/22';
$route['apartments/roommates'] = 'listings/index/14';
$route['apartments/listings'] = 'listings/index/15';
$route['apartment-alerts'] = 'notification/add_notification';
$route['apartments/listings/([0-9]-(beds))'] = 'listings/index/$1'; 


Like I said, the site itself seems to be working fine, but I can't figure out what's causing these errors to show up in the logs. I've tried searching for answers, but they all seem to be dealing with 404 errors that are showing up on the site, and are actual resources that should be on the server. If it's just bots, is there anyway to stop these errors from clogging up my log files? Any help would be greatly appreciated!