You are looking at the HTML representation of the XML format.
HTML is good for debugging, but is unsuitable for application use.
Specify the format parameter to change the output format.
To see the non HTML representation of the XML format, set format=xml.
See the complete documentation, or API help for more information. 
<?xml version="1.0"?>
<api>
  <query-continue>
    <allfileusages afcontinue="Bactris_setosa_seedling_HU.jpg|5443" />
  </query-continue>
  <query>
    <allfileusages>
      <f ns="6" title="File:BAsselinia gracilis solitary.jpg" />
      <f ns="6" title="File:BAsselinia pancheri.JPG" />
      <f ns="6" title="File:BECCARIOPHOENIX NN.jpg" />
      <f ns="6" title="File:BEntinckia condapanna Matt.jpg" />
      <f ns="6" title="File:BISMARCKIA SBG.JPG" />
      <f ns="6" title="File:BRahea calcarea petioles UCB.jpg" />
      <f ns="6" title="File:Bactris setosa JM.jpg" />
      <f ns="6" title="File:Bactris setosa Leu Gardens young plant.jpg" />
      <f ns="6" title="File:Bactris setosa Ralph.JPG" />
      <f ns="6" title="File:Bactris setosa Ralph again.JPG" />
    </allfileusages>
  </query>
</api>