(S (S (NP (NP (BASENP (DT A) (NN gathering) (NN area)) (PP (IN for) (BASENP (DT the) (NNS butterflies)))) (ADJP (JJ northwest) (PP (IN of) (BASENP (NNP Mexico) (NNP City))))) (VP (VBD was) (VP (VP (VBN affected) (ADVP (RB particularly) (RB hard))) (PP (IN by) (NP (NP (BASENP (JJ severe) (NN weather)) (BASENP (DT this) (NN winter))) (COMMA ,) (SBAR (WHNP (WDT which)) (S (VP (VP (VBD killed) (BASENP (NN 50) (NNS people))) (PP (IN in) (BASENP (DT the) (NN region))))))))))) (PERIOD .))