PEMPHIGUS-OBESINYMPHAE, A NEW AMERICAN APHID SPECIES WITH DEFENDERS AND SWOLLEN NYMPHS (HOMOPTERA, APHIDOIDEA, PEMPHIGIDAE)

Pemphigus obesinymphae, n. sp., which is closely allied to P. populitr ansversus Riley, was discovered in Arizona and Utah and is described h ere. The new species forms galls on leaf petioles of Populus fremontii Watson, and produces 1st instar nymphs that possess heavy sclerotizat ion and stout legs. The 2nd and 3rd instar nymphs are swollen and look superficially like wingless adults. The fundatrix, the 1st instar, 2n d instar and adult (alate) fundatrigeniae, the 1st instar exule deposi ted by the alate, the sexupara, and the gall are described. The differ ences found between the new species and the most similar previously de scribed species, P. populitransversus and P. knowltoni Stroyan, are gi ven.