Workbook

Gerrinae is one of four subfamilies in Gerridae - and the only subfamily represented south of Sydney (Insects of Australia, CSIRO, 1991, p484).

Superficially, these insects look like Tenagogerris euphrosyne - the most widely reported species …

Not Limnogonus:

• the medial stripe along the pronotal lobe is NOT pale (it is dark)

• also, the 1st (basal) antennal segment is NOT distinctly shorter than 2nd & 3rd, combined (it appears to be nearly the same length)

Not Aquarius:

• anterior pronotum does NOT have a pale medial stripe (it has a dark stripe, flanked by two pale patches)

• fore femora NOT uniformly dark (they are pale, with a longitudinal dark stripe)

• also, the 1st (basal) antennal segment is NOT distinctly longer than 2nd & 3rd, combined (it appears to be nearly the same length)

Not Limnometra:

• fore femora NOT uniformly pale (they have a dark, longitudinal stripe)

• also, the 1st (basal) antennal segment is NOT distinctly shorter than 2nd & 3rd, combined (it appears to be nearly the same length)

Not Tenagogonus:

• the 1st (basal) antennal segment is NOT distinctly shorter than 2nd & 3rd, combined (it appears to be nearly the same length)

  *NOTE: the single species that Anderson & Weir list for this genus - Tenagogonus australiensis - is now in the genus Tenagogerris.

Therefore it IS Tenagogerris. It matches the description of the genus, including:

• the 1st (basal) antennal segment is almost as long as the 2nd & 3rd, combined

• pronotum pale with dark median strip throughout. (note: some Tenagogerris species have a dark pronotum)

• pronotum of macropterous form is widened at humeral points, and then rounded posteriorly

There are 4* species in this genus:

It is T. euphrosyne. This species is distributed throughout the east coast, from north QLD to Vic

NOT T. femoratus, as this has a uniformly dark pronotum with 2 pale spots.

NOT T. pallidus, as the head and pronotum have only indistinct dark marks.

T. femoratus and T. pallidus have only been recorded in NT and WA.

*Note: it is not Tenagogerris australiensis, for the reasons stated above.

Aquarius antigone and Tenagogerris euphrosyne are the only two species of Gerrinae which we get in eastern NSW (see ref, page 291). The two species are very often found sharing the same water body, although A. antigone is not usually found on the coast.

Reference:

Anderson, N.M & Wier, T.A. 1997. The Gerrine water striders of Australia (Hemiptera: Gerridae): taxonomy, distribution and ecology. Invertebrate Taxonomy 11, 203-299

This is a workbook page … a part of our website where we record the observations and references used in making species identifications. The notes will not necessarily be complete. They are a record for our own use, but we are happy to share this information with others.