Pison argentatum (Shuckard)

Swezey, O. H., 1942, Wasps of Guam, Insects of Guam I, Honolulu, Hawaii: Bernice P. Bishop Museum, pp. 184-187 : 185

3. Pison argentatum (Shuckard) .

Pisonites argentatus Shuckard , Ent. Soc. London, Trans. 2: 79, 1837.

Pison argentatum (Shuckard) Bingham, Fauna Brit. India, Hymenopt. 1: 220, 1897.

Piti,April30, May 19, 24, 30; June 1, 3, 13; July5, 28 ; Aug.9; Sept.13; Oct. 29; Nov. 6, Swezey, Usinger; Merizo, June 11, Swezey .

Among the wasps collected by Fullaway in Guam in 1911 (in Bishop Museum) there are at least four species of Pison , all undetermined, and no P. argentatum among them. In 1936 we procured more specimens of P. argentatum than of all the others. We have 21 specimens of P. argentatum , all but one from Piti, where they were quite common in and about our residence. The little mud nests were common on walls and in corners of back rooms. These nests are made up of one to six cells in which the wasp stores up small spiders on which its larvae feed. There is considerable parasitism by Melittobia hawaiiensis , a tiny parasite whose larvae feed externally on the wasp larvae. There may be up to 100 parasite larvae on one wasp larva. On May 19, a nest containing 6 cells was collected on the scale shed at the Agricultural School, Piti, each cell containing a Pison cocoon in which were tiny exit holes where parasites had issued; hence, a parasitism of 100 percent. On September 24, several nests were collected and examined at the residence. These nests totalled 19 cells, the contents of which were: four with dead pisons; one with dead spiders, one with caterpillars stored by Pachodynerus nasidens ; two with roach egg case; ten had cocoons showing exit holes of MeZ,ittobia;one had living pupae of Melittobia . In this nest, the parasitism would have been at least 56 percent.

This wasp occurs in Madagascar, India, Philippines, and Hawaii. It has undoubtedly become introduced into Guam in somewhat recent years, from Hawaii or the Philippines.