Comparative anatomy of the digestive tract between three species of scale insects (Homoptera: Coccoidea)

This research attempted to examine and compare various areas of the internal anatomy in scale insects for relationship studies. Three major aspects of internal anatomy were examined: the digestive tract in three species of female scale insects, the cephalic region of males in two species of scale insects and the blood cell types in the female of a mealybug, Phenacoccus gossypii Townsend and Cockerell.

Species were collected and processed for histological microtechnique, examined with a brightfield light microscope and characters measured. Some of the specimens were examined with a computerized image analysis system coupled to a microscope. Comparative analysis of measurements was subjected to a non-pooled Students T-test for significance.

Comparisons between the females revealed significant differences in 5 of the 18 areas studied. Comparisons between the two male species revealed no significant differences, even though there was morphological contrast. Examination of the blood in the Mexican mealybug produced four blood cell types.

Results of this study revealed evidence that there is a gradient of characters, generalized in the Mexican mealybug through the Tuliptree scale and specialized by the Euonymous scale, based on anatomy of the digestive tract in the females. The study in the males produced similar results. Hemolymph in the Mexican mealybug revealed a generalized cell type pattern similar to other members of the same order.