140 MR. LUBBOCK ON TWO AQUATIC HYMENOPTERA. 
According to the characters which have been regarded by Mr. Walker as of generic 
value in this group, P. natans would form the type of a new genus. I am, however, un- 
willing to multiply divisions which perhaps have already been carried too far. 
For my second species, however, it seems quite necessary to found a new genus, which 
I propose to call Prestwichia, after my friend Mr. Prestwich, one of our most eminent 
geologists. When this paper was read, I proposed for this species the name 011 
Mr. Busk, however, has pointed out to me that the name was already applied to a genus 
of Polyzoa*. The generic description, for which I am indebted to Mr. Walker, will 
stand as follows :— 
Genus PRESTWICHIA, n. g. 
Fem. Corpus angustum. Caput transversum. Antenne graciles, subclavate, inar- 
ticulate ; clava longi-fusiformis. Thorax brevis. Abdomen sessile, longi-conicum, 
subeompressum, thorace plus duplo longius. Oviductus vagina lanceolata, abdo- 
minis dimidio longior. Pedes longi, graciles; tarsi 4-articulati; ale longs, fim- 
bria longissima ; anticee anguste, postiese setiformes. 
Female. Body narrow; head transverse, as broad as the thorax.  Antenn:e slender, 
subclavate, 10-jointed, as long as the head and the thorax; 1st joint or scape nearly 
. as long as the flagellum; 2nd, 3rd, 4th, 5th, and 6th joints equal in thickness, succes- . 
sively decreasing in length; 7th fusiform; 8th, 9th, and 10th forming an elongate- 
fusiform club. Thorax short. Abdomen sessile, elongate-conical, slightly compressed, 
more than twice longer than the thorax. Sheaths of the oviduct lanceolate, more than 
half the length of the abdomen, proceeding from the tip of the latter. Legs long, 
slender; tarsi 4-jointed, joints successively decreasing in length; middle legs longer 
than the fore legs; hind legs stouter and much longer than the middle legs. Fore wings 
long, narrow, without veins, fringed with hairs which are more than twice longer than 
the breadth of the wing. Hind wings represented by a filament whose hairs are nearly 
as long as those of the fore wings. 
PRESTWICHIA AQUATICA, n. Sp. 
Fem. Nigra; antennis, thorace postico, oviductu pedibusque pallide testaceis; alis 
anticis cinereis. 
Female. Black. Antenne, hind part of the thorax, sheaths of the oviduct, and legs 
pale testaceous. Fore wings cinereous, hairs black. Length of the body ‘05 of an inch; 
the wings a little longer. 
The antennz are short, being only 45th of an inch in length. They consist of six or 
seven segments; the first is long, and near the apex shows a trace of a division. 
Assuming, from the analogy of Trichogramma evanescens, that this is a true joint, the 
second segment is short and round. The third is longer, and increases somewhat in 
size towards the apex; the fourth is similar in shape, but smaller. The rest of the organ 
* While this would have been some slight acknowledgment of the numerous ways in which Mr. Walker has put his 
great knowledge at my disposal, it was certainly no more than a just compliment to one who has so much increased 
our acquaintance with this department of entomology. 
