Life tables were constructed for six cohorts of immature stages of the floodwater
mosquito
Ochlerotatus albifasciatus
(Macquart) in a park in Buenos Aires, highlighting the mortality attributable
to the parasitic nematode,
Strelkovimermis spiculatus
Poinar
&
Camino. Two cohorts were selected to compare parasite incidence in all mosquito
stages when low and high parasitism occurred. Development time of
Oc. albifasciatus
from first instar to adult was 7.7-10 days in the spring, 6 days in the summer,
and 10.9-21.9 days in the fall. Survival was estimated as 0-1.4% in the spring,
2% in the summer and 0.2-4.4% in the fall. The highest
"
K
"
value (Killing power) occurred during a fall cohort when prevalence of the
parasite was 86.9%, and the lowest in a spring cohort. Parasitism occurred
during all seasons, but
S. spiculatus
persisted to adult only in the summer and fall, when adult mosquitoes developed
from parasitized third and fourth instars larvae. The abundance of
S. spiculatus
differed between old and young larvae only when parasite prevalence was the
highest. Although pupae and adults of
Oc. albifasciatus
were parasitized, no pupal mortality attributable to parasitism was recorded.
The proportion of parasitized adults ranged from 14.2% and 5.7% in the two
cohorts compared. Pupal wet weight and adult wing lengths did not differ between
parasitized and unparasitized individuals.
