Eggs and nymphs of
Triatoma dimidiata
were described using both light and scanning electron microscopy. The
egg body and operculum have an exochorion formed by irregular juxtaposed polygonal cells; these cells are without
sculpture and the majority of them are hexagonal in shape. The five instars of
T. dimidiata can be distinguished
from each other by characteristics of the pre, meso and metanotum. The number of setiferous tubercles increases
progressively among instars. The sulcus stridulatorium of 1st instar nymphs is amorphous, showing median parallel
grooves; from the 2nd instar on the sulcus is, progressively, elongate, deep and posteriorly pointed with stretched
parallel grooves. All instars have a trichobothrium on the apical 1/3 of segment II of the antenna. The opening of the
Brindley’s gland is on the mesopleura. Fifth instar nymphs have an apical ctenidium on the ventral surface of the fore
tibia. Dorsal glabrous patches are found on the lateral 1/3 of abdomen. Bright oval patches are found on the ventral
median line of the abdomen, from segment IV-VI; 1st instar nymphs lack these patches. Abdominal dorsal plates are
present from the 1st-5th instars; the 1st instar also contains a rectangular plate in segment IX. From the 2nd instar
on, variably-shaped plates are present on segments VII to IX. Morphometric data were also obtained and proved to
be useful for distinguishing
T. dimidiata instars.
