Spiders can be recognized by counting their legs
  Spiders are arthropods that can be distinguished from their closest relatives, the insects, by counting their legs. Spiders have 8, insects just 6. Spider graphs are a very restricted class of graphs that naturally appear in the context of cograph editing. The vertex set of a spider (or its complement) is naturally partitioned into a clique (the body), an independent set (the legs), and a rest (serving as the head). Here we show that spiders can be recognized directly from their degree sequences through the number of their legs (vertices with degree 1). Furthermore, we completely characterize the degree sequences of spiders. 
Sarah Berkemer, Ricardo Chaves, Adrian Fritz, Marc Hellmuth, Maribel   Hernandez-Rosales and Peter F. Stadler
cs.DM