470 MODERN CLASSIFICATION OF INSECTS. 
great development of the thorax and the rudimental state of the ab- 
domen* (De Geer, tom. ili. t. 16. f.16.). In the full-grown larva of 
Velia, the abdomen is greatly enlarged in size, being still broader in 
proportion than in the imago ; the thoracic segments are still separate 
and visible (Schummel, Ploteres, t. 2. f.2.b, c, d.). In the pupa of 
Gerris, the prothorax is short, the mesothorax large, with a large 
scutellum, partially grooved down the middle, and two separatet+, 
large, and very shining black wing-cases, half covering the abdomen 
(fig. 120. 3.); and the tarsi have only one joint. The wingless ima- 
gines of Velia and Gerris have the prothorax large, but truncate be- 
hind, exposing the other thoracic segments; but, in the winged ones, 
the prothorax is produced behind into a scutellum-like process. 
A remarkable and minute species of this family, found in France, 
was first described, under the name of Velia pygmeza, by Dufour, who 
observed only two or three with wings out of some hundreds of speci- 
mens. The Rev. L. Guilding discovered another species, most closely 
allied to this, in St. Vincent's, which I described under the name of 
Microvelia pulchella, as it differed generically in some respects from 
Velia. This species must also have been most abundant, as Mr. 
Hope (who possesses Mr. Guilding’s specimens) has very great num- 
bers ; but almost all are winged. Subsequently Dr. Burmeister hyper- 
critically changed my generic name to Hydreessa, altered L, Dufour’s 
specific name, and inconsiderately gave my West Indian species, and 
Dufour’s French one, as synonymous. Mr. Curtis, in 1838, figured L. 
Dufour’s species (which I first discovered in England, fifteen years 
ago, amongst aquatic plants on Wandsworth Common, and at the 
roots of grass in Battersea Fields), under the name of Hydreessa pyg- 
mea, from specimens then recently found by Mr. Haliday in Ireland. 
The wingless specimens of this little group have much the appearance 
of minute larvae of Velize; but the abdomen is fully developed. 
Hebrus pusillus W7k.{, another minute species, found amongst 
aquatic plants, and which I have also illustrated in the same me- 
moir, appears to form a connecting link between these insects and 
* Jtis on this account that I am inclined to consider the oceanic species, figured 
by Eschscholtz, as forming his genus Halobates, as not arrived at the imago state 
One species of this genus is described by Templeton ( Trans. Ent. Soc, vol. i.), cap- 
tured midway between Africa and America. 
+ Schummel’s tab. 3. fig. $. is incorrect in this respect. 
$ Dr. Burmeister has misapplied this specific name, giving it to a North Ame- 
rican species, and another name to our species which he had found near Berlin, 
+ 
