Diastole: that regular expansion of the heart that draws the blood inward: see systole.
Dichaetae: a group of brachycerous Diptera with a proboscis consisting of two parts: Muscids, etc.
Dichoptic: Diptera; eyes separated by front: not contiguous: see holoptic.
Dichotomous: forked: dividing by pairs.
Dichromatism: the possession of two color varieties.
Dictyoptera: an ordinal term applied to the roaches: also more generally to the Orthoptera. {Scanner's comment: Roaches are now classed as Dictyoptera, and Orthoptera are now distinct from Dictyoptera }
Didactyle -us: two-toed: with two tarsi of equal length.
Didymus: double: geminate.
Difformis: irregular in form or outline: not comparable; anomalous. Diffracted: bending in different directions.
Diffuse: spreading out; without distinct edge or margin.