Dinámica poblacional de Telenomus fariai (Hymenoptera: Scelionidae). I. Efecto de la carencia de huéspedes (Triatoma phyllosoma) (Hemiptera: Reduviidae) sobre la producción de progenie

JORGE RABINOVICH

Acta Biológica Venezuelica

Universidad Central de Venezuela

Año: 1970 p. 5 - 21

0001-5326

Four generations of the parasite Telenomus fariai COSTA LIMA, 1927, when reared in the laboratory at 26°C +- 1°C and 60-90 R. H., were subjected to different degrees of availability of their host (Triatoma phyllosoma eggs). The increasing ratio of number of parasites over the number of hosts (scarcity) was used as an independent variable, and a twofold measure of its effect was used: (a) the progeny produced per host egg, and (b) the progeny produced per parent. The number of offspring produced per host egg increased to a maximum of 9 wasps per egg at scarcity values of 1.5 and 2.0 (that is to say, when two host eggs were available for every three adult parasites, or when two host eggs were available for every four adult parasites) and then decreased to become stabilized at approximately seven wasps per egg. The only statistically significant differences between means were those corresponding to the following pairs of scarcity values: 0.25 and 1.0, 0.25 and 1.5, 0.5 and 1.5, 0.25 and 2.0 and 0.5 and 2.0. There was also a marked effect of scarcity of hosts upon the offspring number per parent (correlation coefficient r= -0,9715). The curve describing this effect was a monotonically decreasing one and was fitted to the equation y = 11.93 (0.642)^X, where 11.93 represents the maximum possible offspring number produced per parent even with an unlimited number of hosts available; 0.642 may be interpreted as an "interference" or density factor, that is, the factor by which every increase in scarcity of hosts decreases the progeny produced per parent. Also the elasticity was calculated as a density index, and the result given by the equation Ex (y) = -0.1927 x shows that the effect is not isoelastic, that is to say, for every unit increase in scarcity there is always a greater percentage or fraction in the decrease of the number of offspring per parent.