1912] Aquatic Hymenoptera in America. 67 
Antenne 8-jointed, consisting of scape, pedicel, 1 ring joint, 
2 funicle joints and a 3-jointed club. Scape compressed, 
elongate-oval; pedicel as long as the first joint of funicle and 
ring joint, elongate-obconic; first funicle joint cylindrical, 144 
times as long as the second; second slightly oval; club elongate- 
oval, 1-5 longer than the funicle. Anterior and middle femora . 
slightly enlarged medially, the posterior femora more distinctly 
enlarged. Anterior and middle tibiza of about same width 
throughout. Posterior tibia somewhat enlarged distally and 
slightly narrowed just before the tip. First and second posterior 
tarsal joints of equal length, the third somewhat shorter. 
Front wings very narrow, 20 times as long as broad. Mar- 
ginal cilia very long and evenly spaced, those on the posterior 
margin four times as long as the wing is wide. Marginal cilia 
are interspersed with a submarginal row of short sete. 
. & Length .6 mm. Similar to the female. Antenne 8-seg- 
mented, consisting of a scape, pedicel, a ring joint, 5 funicle 
joints, the last three more closely united. Scape compressed; 
pedicel obconic; ring joint distinct; first funicle joint about 1144 
times longer than second, thicker at base than apex. The 
remaining joints sub-equal in length, the last two thicker than 
the preceding. Apical joint pointed at tip. Antenne clothed 
with stiff setaze, which are longer than those of the female. 
Limnodytes gerriphagus Marchal. 
On June 16, 1911, we reared a species of Proctotrypide from 
the eggs of a water strider (Gerris remigis). Both males and 
females were observed swimming actively under water by means 
of their wings. They readily broke the surface film and made 
their escape flying in the air. They were observed to re-enter 
the water and examine carefully the surface of the leaf as if 
searching for the eggs of their host. The eggs of Gerris are laid 
in a single row in gelatine on the under side of the floating 
leaves of aquatic plants. The females were observed oviposit- 
ing in the eggs of Gerris. In the field several of these parasites 
were found on the under side of a floating leaf on the egg mass 
of Gerris. Only a single parasite emerged from each egg. 
We have determined this species as Limnodytes gerriphagus 
Marchal, described in 1900 from specimens reared from the eggs 
of Gerris collected in the vicinity of Paris. Although our 
specimens agree with his descriptions and figures, yet to be 
