SYNOPTICAL KEY. TO THE APHIDIDAE OF MINNESOTA I5I 
(144) PEMPHIGUS POPULIVENAE Fitch, 1859 
Found in a compressed gall on the midvein of balsam poplar. 
(Pachypappa Koch.) 
(145) PEMPHIGUS PSEUDOBYRSA (Walsh) Thomas, 1879 
Found in a widely open, somewhat compressed gall on the midvein of 
Cottonwood leaves; eventually the whole leaf folds ventrally from 
the sides. (Pachypappa Koch.) 
135. Genus MORDWILKOJA Del Guercio, 1909. Type: Byrso- 
crypta vagabunda Walsh, 1862. Spur of the terminal antennal segment 
very long for a Pemphiginae; much longer than the basal part; the 
marginal sensoria are distributed on the spur. 
(146) MORDWILKOJA VAGABUNDUS (Walsh) Del Guercio, 1909 
The spring generation forms a very large and irregular gall et the 
tip of the branches of cottonwood. 
136. Tribe HORMAPHIDINI. Antennae of the migrant 3- to 
5-jointed; sensoria annulate; cornicles usually wanting; cauda distinct 
and globate, and anal plate emarginated; media of the fore wings 
simple, and the cubitus appearing as a branch of the anal; hind wings 
with one or two oblique veins. The Hormaphidini represent an ex- 
treme development of the Pemphiginae line, and should, probably, 
be included with the Vacunini in the Phyllaphidea group. Two genera 
are recognized in the tribe: 
a. Antennae have three segments in the migrant...... Genus HORMAPHIS 137 
b. Antennae have five segments in the migrant..Genus HAMAMELISTES 138 
137. Genus HORMAPHIS Osten-Sacken, 1861. Type: Byrso- 
crypta hamamelidis Fitch, 1851. Fundatrix and migrant with only 
three segments to the antennae. Galls are found on witch-hazel. The 
genus is not known from Minnesota. 
138. Genus HAMAMELISTES Shimer, 1867. Type: Hamame- 
listes spinosus Shimer, 1867. The fundatrix with four segments to 
the antennae and the migrant with five. Forms a spinous gall on 
witch-hazel. 
(148) HAMAMELISTES PAPYRACEAE (Oestlund) 
Pergande considered this the seme as spinosus, but this may be 
considered an open question. The above form is rather common 
here as well as in the northern parts of the state, one or two hun- 
dred miles from the nearest witch-hazel brush, which enters the 
state only in the extreme southeastern corner. 
