  We report here on terahertz (THz) digital holography on a biological
specimen. A continuous-wave (CW) THz in-line holographic setup was built based
on a 2.52 THz CO2 pumped THz laser and a pyroelectric array detector. We
introduced novel statistical method of obtaining true intensity values for the
pyroelectric array detector's pixels. Absorption and phase-shifting images of a
dragonfly's hind wing were reconstructed simultaneously from single in-line
hologram. Furthermore, we applied phase retrieval routines to eliminate twin
image and enhanced the resolution of the reconstructions by hologram
extrapolation beyond the detector area. The finest observed features are 35
{\mu}m width cross veins.
