The soldiers of C formosanus resemble those of C gestroi. Both species have a large fontanelle, when viewed from above, both also have a tear drop-shaped head;
The soldiers of two species may be separated as:
- Coptotermes gestroi soldiers have one pair of hairs near the rim of the fontanelle and the lateral profile of the top of the head just behind the fontanelle shows a weak bulge
- C. formosanus has two pairs of hairs that originate around the fontanelle and the lateral profile of the top of the head just behind the fontanelle do not show a weak bulge,
The alates of these two species may be separated as:
- C. gestroi combined body and wing length 13-14mm, maximum head width 1.4mm; colour on head, pronotum, and dorsal abdomen dark brown.
- C. formosanus combined body and wing length 14-15 mm, and maximum head width 1.5mm; colour on head, pronotum, and dorsal abdomen entirely a lighter yellow-brown or orange-brown.
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