Larrini (CRABRONINAE) — Life in a Southern Forest

Workbook

In my ongoing crabronid project, I have left this tribe to last … perhaps because we rarely see them here in the forest. It is also a rather tricky group. The genera can be difficult to distinguish in all but the clearest set of field photos. Even the features that distinguish the two subtribes – the ridges and depressions of the frons – can be a challenge to visualise. Indeed Bohart & Menke (1976) emphasise the problem of differentiating Larra from Liris on morphological grounds, commenting “…(one could)… unite Liris and Larra, because the characters which separate the two are rather weak, expecially in the male” (p. 240).

So that’s my justification for considering it a tricky group. Below is my first reconciliation attempt.

Back to Crabronid Hub

The following table and images are an aid to genus-level identification of Australian Larrini.

click image to open/download latest version as pdf (<100kb)

What to look for

The summary table above emphasises the importance of the hind ocelli and the shape of the frons, as well as tarsomere shape and the hairiness (or otherwise) of the pygidial plate. All well and good, but it’s instructive to see what these features actually look like in a photo.

I’ve taken advantage of the sightings shared on iNaturalist. Thank you to every person out there, with a camera, recording and sharing what they see in nature :)

Featured

Tachysphex - ocelli and surrounding area

Hind ocelli ovoid, without long tails.

Note too the circular swelling between the mid and hind ocelli (dotted line), plus the mid ocellus NOT in a broad depression.…. both are features diagnostic for the tribe Gastrosericina

https://inaturalist.ala.org.au/observations/106967174

Tachysphex – ocelli

Hind ocelli oval, their long axes forming a wide angle (dotted lines) and without a long tail.

Mid ocellus NOT in a deep, transverse depression.

https://inaturalist.ala.org.au/observations/197284468

Tachytes - ocelli & adjacent head shape

Elongate hind ocellar scar, ‘golf-club shaped’, with tails nearly parallel. Note that the space between the mid-ocellus and the end of the tail is less than the length of the tail.

Also note the circular swelling between the mid and hind ocelli (dotted line). This is a feature of the subtribe Gastrosericina.

https://inaturalist.ala.org.au/observations/219086289

Tachytes - ocelli

The characteristic, long-tailed hind ocellar scar.

https://inaturalist.ala.org.au/observations/199091283

Tachytes - ocelli

The angle and lighting in this image really highlight the shape of the hind ocellar scars.

https://inaturalist.ala.org.au/observations/150637362

subfamily Larrina - ocellar depression & frons

The deep, broad depression housing the mid ocellus distinguishes the subfamily Larrina, as does the transverse swelling below the mid ocellus (dotted line).

https://inaturalist.ala.org.au/observations/212562147

Liris - hind tarsomeres

As this is a female, the hind tarsi and pygidial plate can be used to distinguish between Larra and Liris. The last tarsomere is strongly angled (‘bent’), and bears long claws.

The pygidial plate of Liris is described as “usually extensively setose”. I find this difficult to be confident from a field photo.

https://inaturalist.ala.org.au/observations/212562147

subtribe Larrina – mid ocellus

Mid ocellus in a broad, deep depression … subtribe Larrina.

https://inaturalist.ala.org.au/observations/83608262

Liris – last tarsomere of hind leg

This is a female in the subtribe Larrina, so the shape of the last tarsomere can be useful. In this image the sharp bend and long claws are particularly obvious. Note, however, that not all Liris have this feature … but apparently no Larra do.

https://inaturalist.ala.org.au/observations/83608262

subfamily Larrina - ocellar depression & frons

The deep, broad depression housing the mid ocellus distinguishes the subfamily Larrina, as does the transverse swelling below the mid ocellus (dotted line).

Note also the very shiny frons & vertex, suggestive of Larra rather than Liris (but see details of tarsomeres for confirmation of genus).

https://inaturalist.ala.org.au/observations/200081220

Larra - hind tarsomeres

As this is a female, the last tarsal segments of the mid and hind legs can be used to distinguish Larra from Liris. Here the segment is evenly arched, NOT sharply bent as in Liris, and the claws are short.

Note also the hairless, shiny pygidial plate is consistent with Larra.

https://inaturalist.ala.org.au/observations/200081220

Larra – orbital sulcus, antennal texture

In Larra, the upper inner angle of the eye is often bordered by a deep groove (‘sulcus’) … this is absent in Liris.

The scape and pedicel in many Larra species is conspicuously shining, in contrast to the remaining antennal segments. Again, this is not the case in Liris.

https://inaturalist.ala.org.au/observations/252847348

Note: many photos taken in the field cannot be confidently identified to genus, or even sub-tribe. With this group of wasps, the angle of the photo is every bit as important as the resolution (i.e. quality) of the image.

Liris vs spider wasp

It is not uncommon for Liris to be mistaken for spider wasps, particularly Turneromyia or Ctenostegus. The black-&-silver patterning, relatively long legs, and behaviour can appear quite similar. The key differences are in the eye shape, ocelli, and the shape of the pronotum.

Bits & Pieces

A mixed collection of original descriptions and published illustrations.

Larra alecto (Smith 1858)

Larra psilocera (Kohl 1884)

Larra melanocnemis (Turner 1916)

Larra femorata (Turner 1908)

Dicranorhina intaminata (Turner 1910)

Dicranorhina (Bohart & Menke 1976)

Tachytes formosissimus (Turner 1908)

Tachytes & Tachysphex - ocelli (Bohart & Menke 1976)

Larra & Liris - pygidium (Bohart & Menke 1976)

Tachytes & Tachysphex - pygidium (Bohart & Menke 1976)

Larra – hind tarsomere (Bohart & Menke 1976)

Liris – hind tarsomere (Bohart & Menke 1976)

Tachysphex - fore tarsomeres (Bohart & Menke 1976)

Tachytes - hind femur (Bohart & Menke 1976)

Bohart, R.M. & Menke, A.S. 1976. Sphecid Wasps of the World: a Generic Revision. Berkeley: Univ. California Press

Kohl, F.F. 1884. Neue Hymenopteren in den Sammlungen des zoologischen Hof-Cabinetes zu Wien. ii. Verhandlungen der Zoologisch-Botanischen Gesellschaft in Wien 33: 331-386

Smith, F. 1858. Catalogue of the hymenopterous insects collected at Sarawak, Borneo; Mount Ophir, Malacca; and at Singapore, by A.R. Wallace. Journal of the Proceedings of the Linnean Society of London 2: 42-130

Turner, R.E. 1908. Notes on the Australian fossorial wasps of the family Sphegidae, with descriptions of new species. Proceedings of the Zoological Society of London 1908: 457-535 pl. xxvi

Turner, R.E. 1910. New fossorial Hymenoptera from Australia. Transactions of the Entomological Society of London 1910: 407-429 pl. 50

Turner, R.E. 1916. Notes on fossorial Hymenoptera. XX. On some Larrinae in the British Museum. Annals and Magazine of Natural History 8 17: 248-259

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.