Studies on the Biology of Pentatomid Bugs of the Genus Rhopalimorpha Dallas (Heteroptera) By J. G. Pendergrast, Auckland [Read before the Auckland Institute, August 15, 1951; received by the Editor, August 29, 1951]] Summary Observations on the biology and life history of Rhopalimorpha obscura White and R. lineolaris Pendergrast (Heteroptera, Pentatomidae) have been carried out in the field and on captive material. The two species have a similar distribution and frequent the same limited number of host plants, mostly members of the Cyperaceae. Individuals of both species are sometimes found living together. Food plants and the process of feeding are described and the formation of small cones of hardened secretion around the points of insertion of the stylets is noted. When starved, a carnivorous habit may be assumed. Experiments indicate that rise in temperature is the chief factor in stimulating copulation. Copulation is not a prerequisite for oviposition, but appears to be necessary for the proper formation of the eggs and for the production of the normal number. The probable part played by the modified lobes of the small ovipositor in the transmission to the eggs of bacterial symbionts is discussed. During oviposition the female rapidly taps a pair of setose areas on the abdominal venter with the hind legs. There is some evidence from histological preparations that these areas have a sensory function. The eggs of the two species differ in size, shape, colour and in the number in each set. A single case of parasitism of the eggs by a Scelionid has been observed. With the exception of the valuable paper of Myers (1926) on the biology of the New Zealand Heteroptera, there appears to have been little published on the habits of the indigenous members of the Pentatomidae. The following account records observations on the relatively common grass- and sedge-haunting bugs of the genus Rhopalimorpha Dallas (Pentatomidae; Acanthosomatinae) which is represented in New Zealand by two species, R. obscura White and R. lineolaris Pendergrast. The presence of the latter was unknown to Myers, and under the name of R. obscura he has included, in part, notes on the biology and nymphal stages of what is fairly certainly R. lineolaris. Distribution A list of localities has been compiled from published records, museum collections and personal observations. This shows that the two species are found over the two main islands of New Zealand from North Auckland to Otago. They are recorded also from Cuvier, Motutapu, Waiheke, Kapiti and D'Urville Islands. R. obscura alone has been noted from Stewart Island (Howes, 1914), but as the presence of R. lineolaris was unsuspected at that time, there is the possibility that this species was collected but not recognized. The only specimen from the Chatham Islands examined by the writer is the type of R. ignota Hutton and, as noted in a previous paper (1950), this is clearly R. obscura White. In view of their similar distribution on the main islands of New Zealand it would be of interest to discover whether both species are present in the Chathams. Although the two species have a similar general distribution, one or the other may attain local dominance. For example, at St. Heliers, Auckland, over a period of eighteen months, 159 specimens of R. lineolaris were collected and only 5 R. obscura, all these latter from a single plant. In contrast to this, at Paiaka,