Table 1 Differences observed by optical microscopy between three species of Rhodnius in the five nymphal instars
Instars | Species | Characters | ||
|---|---|---|---|---|
Head | Thorax | Abdomen | ||
R. marabaensis | – | – | Segments IV and V are the broadest. Segment I same length as the metanotum | |
First | R. prolixus | – | – | Larger, particularly between segments III and VI. Segment I same length as the metanotum |
R. robustus | – | – | Widens gradually from segment I to IV. Segment I longer than the metanotum | |
R. marabaensis | – | Pronotum form of a trapezium. Mesonotum-metanotum dividing line straight | Straight external limits between segments III and VI | |
Second | R. prolixus | – | Longest pronotum. Mesonotum-metanotum dividing line concave | Maximum width in segment V |
R. robustus | – | Shortest pronotum. Mesonotum-metanotum dividing line straight | Widens gradually from segment I to IV | |
R. marabaensis | Prominent white stripe from the antennal tubercle to the neck | Concavity is not seen | Stripe that has straw-colored marks elongated in each segment | |
Third | R. prolixus | The stripe is not so evident | Concavity near the metanotum | Such marks are neither so elongated nor clear |
R. robustus | Between the clypeus and the antennal tubercles; between the posterior region of the eye and the neck | Concavity is not seen | The marks are not elongated, yet clear | |
R. marabaensis | White stripe is very clear | Pronotum-mesonotum line has a slight sinuosity overlapping a tiny part of the mesonotum | – | |
Fourth | R. prolixus | Stripe present, but narrower | Same as R. marabaensis | – |
R. robustus | Less clear in the intermediate portion | Pronotum-mesonotum line has a concave aspect, the same for the metanotum-abdomen line | – | |
R. marabaensis | Maxillary plate reaches the clypeus (straight), the anteclypeus is curved | Side limit of the anterior wing pads is diffuse and broad | – | |
Fifth | R. prolixus | Maxillary plate surpasses the clypeus (curve), anteclypeus has a trapezoidal shape | Side limit of the anterior wing pads is a clear line | – |
R. robustus | Maxillary plate reaches the clypeus (concave), anteclypeus has a semicircular shape | Side limit of the anterior wing pads is a clear line | – | |