Threat Level: Low

Paratrechina bourbonica is a dark colored, small species with moderately long appendages, eyes that lie within the outline of the head, and rows of long thick and dark hairs. The petiole is upright and, like all formicines, the gaster is armed with an acidopore. There are no characters that can reliably identify P. bourbonica in the field, and an accurate identification is even difficult with the aid of a microscope.

Paratrechina vaga is the species most often confused with P. bourbonica. The most reliable character used to differentiate between them is the amount of appressed pilosity found on the mesopleuron. The mesopleuron of Paratrechina bourbonica is typically covered in a dense pelt of short appressed hairs while that of P. vaga is typically glassy smooth with at most a sparse scattering of short appressed hairs. While this character often works, there are some specimens in which the pilosity appears intermediate.

Wilson and Taylor (1967) offer the following discussion of P. bourbonica:

The workers are most readily separated from the similar P. vaga by their size; the head width of the great majority of individuals range between 0.65 and 0.72 mm...The workers of vaga are extremely variable in the characters just cited with reference to bourbonica; in the study series a few workers can be found that overlap bourbonica in individual characters. The great majority of vaga workers have head widths between 0.45 and 0.62 mm and slightly shorter scapes than bourbonica, and are light to medium reddish brown in body color. It is to be admitted, however, that a few individuals cannot be placed with certainty in either species.

Bourbonica apparently originated from tropical Asia and has been spread by commerce throughout the Indian and Pacific Oceans and to a few localities in the New World tropics.

In Fiji, it appears that P. bourbonica is significantly less common than P. vaga. Little is known about the effects P. bourbonica has on ecological or agricultural systems.

Paratrechina is a diverse genus with many taxonomically difficult species that occur in the Pacific region. If a specimen does not match the description or images of species included in PIAkey, it is very possible that it is either a native species or a different introduced species.

Waist with one segment (petiole) Petiole raised, not flattened Petiole sometimes obscured by gaster
Gaster armed with acidopore
Long, dark, thick hairs produced in pairs on body
Long, dark, thick hairs produced in pairs on head
Eyes inside outline of head
Antennal scape length less than 1.5 times head length
Mesopleuron with many hairs (usually > 20)

	P. bourbonica	P. vaga	P. longicornis
Head
Profile
Antennal scape length relative to head length	< 1.5x length of head	< 1.5x length of head	~ 1.5x length of head
Eyes break outline of face	no	no	yes
Hairs on mesopleuron	abundant (usually > 20)	sparse (usually < 20)	sparse (usually < 20)
Color of hairs	dark	dark	white
	P. bourbonica	P. vaga	P. longicornis

• Antweb: specimen images, data & maps
  
  
• Bolton, B. (1995) A new general catalogue of the ants of the world. Harvard University Press, Cambridge, Massachusetts, 504 pp.
  
  
• Wilson, E.O. & Taylor, R.W. (1967) The ants of Polynesia (Hymenoptera: Formicidae). Pacific Insects Monograph, 14, 1-109.