How to alter image captcha title in drupal 7
use hook_form_FORM_ID_alter() and Form API pre_render function. E.g:

// Explains pre_render. This is when you create a form; 
function feedbackForm($form, &amp;$form_state) {

  $form['#pre_render'][] = 'feedbackForm_pre_render';

  $form['name'] = array(
    '#title' =&gt; t('Ваше имя'),
    '#type' =&gt; 'textfield',
    '#required' =&gt; TRUE,
  );

  $form['actions'] = array(
    '#type' =&gt; 'actions',
  );

  $form['actions']['submit'] = array(
    '#type' =&gt; 'submit',
    '#value' =&gt; t('Отправить'),
  );

  return $form;
}

function feedbackForm_pre_render($element) {
  $element['captcha']['captcha_widgets']['captcha_response']['#title'] = t('Защитный код');
  return $element;
}


You can also use hook_form_alter() function:

function MY_MODULE_OR_THEME_form_alter(&amp;$form, &amp;$form_state, $form_id) {
  dpm($form);

  if($form_id == 'FORM_ID') {
    $form['#pre_render'][] = 'feedbackForm_pre_render';
  }
}