Stick Insect

A rare inhabitant of South America, Metriophasma (Acanthometriotes) crassus is a remarkably colourful member of the Pseudophasmatidae family. First described by the renowned entomologist Morgan Hebard in 1924 in his paper headed 'Studies in the Dermaptera and Orthoptera of Ecuador, this particular species is still very much undescribed.

 

PHOTO CREDIT

Top photo courtesy of Tristan Bawn, bottom photo courtesy of www.flickr.com/andreaskay/albums. A special thank you to the world expert on Neotropical Phasmids, Oskar Conle and Phasmatodea.com for identifying our photograph.

 

HABITAT AND DISTRIBUTION

Metriophasma (Acanthometriotes) crassus has been described from rainforest habitat in Panama, Ecuador and Colombia. We also know of a specimen being recorded in the Manú National Park, Peru.

 

DESCRIPTION 

Metriophasma (Acanthometriotes) crassus is described as being very close to the Metriophasma species, but is thicker and more robust and also has 10 - 12 large spines on its mesonotum (part of its thorax). The body is also said to resemble a heavier species of the Pseudophasma genus. The legs are relatively short and robust, their colour a patchy mix of dark brown and light green (although the holotype was described as buckthorn brown and cinnamon-buff) with reddish joints and tarsi. The long tegmina (hardened forewings designed to hide the hindwings) on the back are a mid-brown colour with light green patches and heavy veination. The thorax and head are a yellow-brown colour, and the thorax spines bright red. The long antennae appear dark brown.

 

The male is quite similar in appearance, but the colour appears different. The thorax and head are a mid-green colour, as are the wing coverings which also have brownish patches. The spines appear orange in colour and the antennae a deep red. The legs are a uniform dark green with red joints and tarsi. The differences may be sexual dimorphism, or it may be that the male is an immature and not yet fully developed. Unfortunately no males have been described in detail yet.

 

The nymphs are a uniform dark green colour. 

 

Metriophasma (Acanthometriotes) crassus - female

 

DIET, BEHAVIOUR AND REPRODUCTION

This species is more active by night (nocturnal), preferring to spend its day camouflaged on leaves or stems in a cryptic posture. The diet consists of plants (especially Philodendron species). The prothorax contains special glands that are capable of emitting a spray as a chemical defense, this is only released if the threat comes into contact with an individual. Females will sometimes raise their wings coverings and wings when retreating from a threat, whereas the male would rather fly away. It is believed that the male is more likely to take flight as his defensive spray glands are half the size of the females.

 

Body length was described as being approximately 75mm and length of pronotum 6mm. It is not clear if the pronotum length is in addition to the body length or included in the measurement. The wings were measured at 39mm. These measurements were based on a female, and with the male having smaller defensive glands, it would suggest the male was smaller in size too as seen in other Metriophasma. For instance, in Metriophasma diocles the male is three-quarters the length of the female, 60mm compared to 80mm.

 

OTHER NOTABLE FACTS

Metriophasma (Acanthometriotes) crassus contains a subgenus. This way of naming places it in the genus Metriophasma, and the subgenus Acanthometriotes (due to its robust body, broad mesothorax and armature thorax). A subgenus is used to differentiate between species of the same genus that may share a common trait that not all the genus members share, but not enough to allow them their own genus.

 

The holotype (single specimen used to describe a new species) on which the species was fully described is a female from San Xavier in northwest Ecuador. A second specimen (known as a paratype) was collected from Paramba Rio Mira, Imbabura in Ecuador. 

 

The male on this page was spotted by Tristan Bawn on a trip to the Manú National Park in Peru. For many years it was left as a '90% possible new species', until it was formerly identified on 10th October 2016. To date no male has been described on paper, so although not a new species it is still an extremely special find.

 

Below is the original sketch of Metriophasma (Acanthometriotes) crassus as described by Hebard in 1924.

 

Hebard - 1924 - Holotype female