AQUATIC HYMENOPTERA IN AMERICA. 
RosBert MATHESON and C. R. Crossy. 
This article is intended primarily to call attention to an 
almost entirely neglected field of entomological research, at 
least in this country, namely—the study of the habits and life- 
histories of those minute hymenopterous insects that have 
assumed aquatic life. In Europe considerable work has been 
done along this line. As early as 1836, F. Walker observed 
Agriotypus armatus (an anomalous Ichneumon fly) descend 
some distance into the water. Von Siebold (1858), W. Muller 
(1888), and others have shown that it is parasitic on Trichop- 
terous larve. In 1863 Sir John Lubbock published his well 
known account of Polynema natans and Prestwichia aquatica, 
both with aquatic habits, the former swimming by means of its 
wings, the latter using its legs. Nothing was known by him 
regarding their earlier stages. Enock, Heymons and Willem 
have since reared Prestwichia aquatica from a variety of insect 
eggs, including Notonecta, Ranatra, Dytiscus and Pelobius. 
In 1908, Heymons reared from eggs of a dragon-fly a Myma- 
rid (Anagrus subfuscus) which although provided with wings 
kept them closed and swam with its legs. He also observed 
Gyrocampa stagnalis, a Braconid, swimming under water by 
means of its legs. Other European workers have made similar 
observations on the same or related species. 
Our notes refer to three species, all reared at Ithaca, N. Y. 
Hydrophylax aquivolans n. gen. and n. sp. 
In September, 1908, Dr. J. G. Needham observed a number 
of minute Trichogrammids swimming by means of their wings 
in an aquarium which contained eggs of Ischnura, probably 
verticalis. These were again observed by him in the summer of 
1911. Nothing is known regarding their earlier stages. 
This species is apparently undescribed and runs to the genus 
Asynacta Foerster in Ashmead’s tables (Chalcis Flies, p. 359, 
1904). Foerster used the name Asynacta in a table in his 
Hymenopteren Studien, II, p. 87, 1856, but no species has ever 
been placed in the genus, and it is therefore a nomen nudum. In 
any case, although the present species agrees with Asynacta 
Foerster in antennal characters it would be separated from that 
genus by the extremely narrow wings which are abnormal to 
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