In situ: in its natural place or normal position.
Instar: the period or stage between molts in the larva, numbered to designate the various periods; e.g. the first instar is the stage between the egg and first molt, etc.: see stadium.
Institia: stria or furrows of equal width throughout.
Instrumenta cibaria: mouth parts of a mandibulate insect as a whole.
Instrumenta suctoria: mouth parts of a haustellate insect as a whole.
Integer: entire: applied to a margin without incisions.
Integument: the outer covering to the insect body.
Inter: between; among.
Inter-alar space: in Odonata; the terga of meson- and meta-thorax.
Interantennal: between the basal segments of antennae.