The biology and ecology of roscious elongatus (shaum): (pyrrhocoridae: hemiptera).

Aspects of the biology and ecology of Roscius elongatus were studied under laboratory and field conditions within the environs of the University of Dar es Salaam campus between March 1993 and March 1994. The life history of R. elongatus includes egg, five nymphal instars and the adult stage. The total larval developmental period was 56.6 ± 6.9 days. The incubation period was 7.6 ± 0.1 days. The pre-aviposition, interoviposition and aviposition periods were 16.0 ± 0.22, 11.25 ± 0.15 and 37.11 ± 0.45 days respectively. The average egg size is 1.122 ± 0.113 mm3, while the average length and width are 1.764 ± 0.02 and 1.104 ± 0.01 mm respectively. The average clutch size is 140 ± 3.28 eggs per female. The maximum number of clutches per female is three. Egg size increases in subsequent clutches while clutch size decreases as the females' age increases. The mean clutch size for the first, second and third clutches are 140 ± 3.28, 71 ± 3.52 and 30 ± 2.07 respectively. Field observations on distribution and abundance of R. elongatus indicate that the species is widely distributed throughout the range of its host plant, Xylotheca tettensis. There is high build up in population during the rainy season. This is the time when there are many X. tettensis plants bearing mature and ripe fruits providing ample food supply. Two species of Roscius were found in the field during the study, R. elongatus and R. illustrius, the former being by far the commonest in all areas visited. Despite being a fruit/seed feeder, carnivorous behaviour was observed on two occasions. Its significance has not been determined. Under laboratory conditions investigations showed that developmental and reproduction processes were significantly influenced by the type of host food plant on which the nymphs are maintained. In this regard results showed that Gossypzum hirsutum and X. tettensis supported all stages of development to adult stage. Sterculia africana supported development up to fifth nymphal stage, while Cezba pentandra supported growth up to third nymphal stage only. The periods taken to complete larval stages were also variable when the nymphs were fed on the seeds of the various host plants.