292 



Hagen: Hymenoptera 



Fig. 12:1. Carapbractus cinctus Walker (Matheson 

 and Crosby, 1912). 



America. Prestivichia aquatica Lubbock 1863 of 

 Europe possibly occurs in the Nearctic region, for 

 Martin (1928) implies that it has been reported in New 

 York. It was placed in the above key in the event that 

 it is established in North America. There are said to 

 be three forms or races of P. aquatica (Henriksen, 

 1922), the typical one having females with well- 

 developed wings and males with rudimentary wings. 

 The second 'form has wings rudimentary in both sexes. 

 The third form has the wings of the females reduced. 

 This species has been recorded from the eggs of 

 Ranatra, Nepa, Aphelocheirus, Dytiscus, and Pelobius 

 (Ruschka and Thienemann, 1913). A maximum of fifty 

 individuals was secured from a single egg of the 

 larger species of Dytiscus (Clausen, 1940). Enock 

 (1889) claims that only the middle legs are used by 

 the adults for swimming, but Henriksen states that the 

 hind legs serve this purpose. Heymons (1908) states 

 that the adults remained under water for five days. 



Hydrophylita aquivolans (Matheson and Crosby) 1912 

 is known from the eastern United States, and has been 

 recorded by Matheson and Crosby (1912) as parasitiz- 

 ing the eggs of Ischnura sp. This species swims by 

 means of its wings. 



Hoffmann (1932) exposed eggs of several species 

 of aquatic insects and eggs of a water mite to Tricho- 

 gramma minutum Riley 1871, but obtained progeny only 

 from the mite eggs. There is no distinct indication 

 that T. minutum actually entered the water for ovi- 

 position, since the adult parasites were found webbed 

 in the scum covering the water mite egg mass. This 

 host record must be considered questionable until 

 supported by further experimentation. If the observa- 

 tion is valid, it would be the first record of any stage 

 of a spider mite to be attacked by an internal parasite. 

 Martin (1928) describes the immature stages of T. 

 minutum and its host range. 



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