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XXIV. Descriptions of some minute Symenopterous Insects. 

 By J. O. Westwood, M.A., F.L.S., fyc. 



(Plate LXXIII.) 



Eead April 4th, 1878. 



JL HE fourth volume of the ' Transactions ' of the Linnean Society (1798) contains the 

 figure and description of an almost invisible Hymenopterous insect, referred by the 

 author, Mr. Shaw, to the Linnean genus Ichneumon, and .described under the name of 

 Ichn. punctum, with a doubtful reference to the Ichn. atomos of Linnaeus. The specimen 

 is stated to have been taken on the surface of a window ; and on various occasions I 

 have taken the same or a closely allied species creeping on windows, and of so minute 

 a size as to be only visible when seen against the light and in motion. The insect is 

 remarkable for its antennae terminating in an oval club (being a female), and the long 

 fringe of hairs with which the edges of the wings are furnished. It is at the present 

 day referred to the subfamily Mymarides among the Proctotrupidae, and to the genus 

 Anaphes of Haliday (Entomol. Mag. i. 269). 



The twenty- fourth volume of the ' Transactions ' of the Linnean Society (1863) adds 

 materially to our knowledge of these minute insects by the publication of a memoir, by 

 Sir John Lubbock, " On two Aquatic Hymenoptera, one of which uses its wings in swim- 

 ming." In this remarkable memoir the author describes two different species — one 

 belonging to the Mymarides, and the other, as it seems to me, to an aberrant group of 

 the Eulophideous Chalcididae. Of the first of these two species as many as twenty-one 

 individuals were observed by Sir John Lubbock, each swimming in a basin of pond-water 

 with the assistance of its wings, and using its legs apparently only for walking, so that 

 its motion under water might almost be called a flight. This insect was at first regarded 

 as identical with Polynema fuscipes of Haliday, but was subsequently considered to be a 

 distinct species, and described under the name of Polynema natans, although that genus 

 possesses 13-jointed antennae in the males, whereas P. natans has only twelve joints in 

 its male antennae. As Sir J. Lubbock did not give any representation of the male 

 antenna, I have represented it in Plate LXXIII. fig. 1, from a specimen of the insect 

 communicated to me by Sir J. Lubbock. "With regard to the genus to which this insect 

 belongs, it is to be observed that Dr. Arn. Eoerster (Hymenopt. Studien, ii. Heft, pp. 118, 

 121) objects to the name Polynema, because there was a fish genus so named previously, 

 and to the synonymous name Eutriche of Nees von Esenbeck (Monogr. Ichn. Min.), 

 because Stephens had given the name of Mitricha to a Lepidopterous genus. He con- 

 sequently proposed for it the name of Cosmocoma. Considering that it is unnecessary 

 and inexpedient to alter such generic names because they happen to have been previously 

 employed in different classes of animals, I should have retained the generic name given 



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