Field of Science

ID for Heather?

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I was recently contacted by Heather Adamson who wanted to know if I could identify the animal in the above picture. She photographed it on an old post in the region of West Coolup, south of Mandurah here in Western Australia. I can tell her that it is some form of Lepidoptera larva (in other words, a caterpillar) and it looks like it may be beginning to weave itself a cocoon. Beyond that, I couldn't say. Do any of my readers have a better idea of what it is than I do?


Update: I shared this post to the Western Australian Insects group on Facebook, and Daniel Heald has suggested that Heather's photo may show the pupa of a lymantriid moth Teia athlophora. This species constructs itself a loose, cage-like cocoon from its own irritant hairs. The male, when he emerges, is a fairly standard looking brown moth, but the female is fat and flightless with only tiny stubs of wings. She will continue to live in and around her pupal cocoon, awaiting visits from courting males.

The Brown Honeyeaters

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Brown honeyeater Lichmera indistincta, copyright JJ Harrison.


Honeyeaters are one of the first groups of birds likely to be noticed by newcomers to Australia (after the crows and magpies, of course). Though generally not large birds, they are active, noisy and often colourful. Individuals or small groups of them will almost invariably be seen around trees in flower, seeking out nectar and squabbling over access to the best blooms.

Here in Perth, one of the more common honeyeater species is the brown honeyeater Lichmera indistincta. This is one of the smaller honeyeaters and as such might be less commonly noted by the casual observer, but it is abundant nonetheless. The brown honeyeater is one of a genus of about ten species of small, slight honeyeaters with slender decurved bills found from the Lesser Sundas of Indonesia to New Caledonia and Vanuatu (Higgins et al. 2008). Lichmera indistincta is the only species found in continental Australia. Most of the species are locally more or less abundant though some have quite restricted ranges, being found only on specific islands. A few are considered near-threatened. Lichmera species are predominantly grey-brown or greenish in colour; perhaps the most strikingly coloured is the black-necklaced honeyeater L. notabilis of the island of Wetar in the Lesser Sundas, which is yellowish-olive above and yellow below, with a striking white throat patch outlined in black.

Indonesian honeyeater Lichmera limbata, copyright Lip Kee.


Lichmera honeyeaters occupy a wide range of habitats but often prefer to be in the vicinity of water, occupying river-side woodlands and stretches of mangroves. One subspecies of the silver-eared honeyeater L. alboauricularis olivacea has a distribution that closely follows river systems in northern New Guinea. Favoured food plants of the brown honeyeater in Australia include Myrtaceae such as Eucalyptus and Melaleuca, and Proteaceae such as Banksia and Grevillea. They will also take small insects and spiders; I suspect that the proportion of nectar to insects in the diet depends on the availability of the former. Nests are open cups constructed of plant matter such as grass and pieces of bark bound together with spider web and other fibres. Small clutches of one to three eggs are brooded by the female alone, taking about two weeks to hatch, though the chicks are fed by both parents. The call of the brown honeyeater, which can be heard year-round, has been rendered as 'sweet-sweet-quarty-quarty'.

Nectar, of course, is not a hugely nutritious food source per volume (being mostly water), and a small bird like a brown honeyeater has to feed fairly constantly to keep itself going. Even though its metabolism slows down when sleeping, a brown honeyeater will still lose about half a gram of body weight overnight (Collins 1981) which is pretty impressive when you consider that the entire bire only weighs about eight grams (imagine if the average lost five kilos every night...) To make up for this loss, the bird feeds most heavily in the early morning, as well as retaining water for the last half-hour or so before going to sleep. And so it is that the honeyeater gets through the night.

REFERENCES

Collins, B. G. 1981. Nectar intake and water balance for two species of Australian honeyeater, Lichmera indistincta and Acanthorhynchus superciliosis. Physiological Zoology 54 (1): 1–13.

Higgins, P. J., L. Christidis & H. A. Ford. 2008. Family Meliphagidae (honeyeaters). In: Hoyo, J. del, A. Elliott & D. Christie (eds) Handbook of Birds of the World vol. 13. Penduline-tits to shrikes pp. 498–691. Lynx Edicions: Barcelona.

The Mancos Saltbush: Life in the Badlands

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Mancos saltbush Proatriplex pleiantha, from here.


Proatriplex pleiantha, the Mancos saltbush, is arguably not much to look at. It never grows very large (only about half a foot in height) and though a single plant may produce a lot of flowers, they are not very showy. Nevertheless, this little fleshy-leaved annual is something of a survivor. It grows on badlands in only a few localities in northern New Mexico and southern Colorado, and may be the only vegetation to be found on the eroded clays that it calls home. It persists in this hostile environment by not persisting; instead, each individual plant will produce hundreds, if not thousands, of seeds during its short life that may lie dormant in the soil for several years, waiting for the flash of rain that will allow it to emerge.

The Mancos saltbush was first described in 1950; its vernacular name refers to the original collection locality near the Mancos River. It was originally described in the genus Atriplex, a diverse cosmopolitan assemblage of herbs and shrubs in the family Chenopodiaceae commonly known as saltbushes and oraches (the garden orache or mountain spinach A. hortensis has long been grown as a vegetable in Europe). However, right from the start it was considered distinctive enough to be placed in its own subgenus, later raised to the status of a distinct genus by Stutz et al. (1990). A molecular phylogenetic analysis by Kadereit et al. (2010) later confirmed that Proatriplex pleiantha is not a direct relative of Atriplex, instead being associated with other small North American Chenopodiaceae genera Grayia and Stutzia. Features distinguishing Proatriplex from true Atriplex include the succulent leaves, the flowers being borne in groups of three to seven in the axil of a single bract, and the presence of a five-segmented perianth around female flowers (Atriplex flowers are borne singly to a bract, and lack a perianth).

Because of its restricted range, the Mancos saltbush may be vulnerable to disturbances in its habitat; for instance, one of its main population centres in New Mexico is in close proximity to the Navajo coal mine. Nevertheless, this species is not currently listed by the US Fish & Wildlife service as being of concern, due to its being locally abundant in the areas where it does occur. Surveys of this species have been complicated by the dependence of its germination on suitable weather conditions: in years with little rainfall, it may appear to be almost absent, but the advent of a wetter year may prove otherwise. All it takes is a decent drop of rain, and you may see the badlands bloom.

REFERENCES

Kadereit, G., E. V. Mavrodiev, E. H. Zacharias & A. P. Sukhorukov. 2010. Molecular phylogeny of Atripliceae (Chenopodioideae, Chenopodiaceae): implications for systematics, biogeography, flower and fruit evolution, and the origin of C4 photosynthesis. American Journal of Botany 97 (10): 1664–1687.

Stutz, H. C., G.-L. Chu & S. C. Sanderson. 1990. Evolutionary studies of Atriplex: phylogenetic relationships of Atriplex pleiantha. American Journal of Botany 77 (3): 364–369.

Who Knows Which Way the Water Flows?

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Dorsal and lateral views of specimens of Trenella bifrons, from Parkhaev (2001).


There is no question that the molluscs are one of the most significant groups of animals in the marine environment. And thanks to the production by many species of mollusc of a hard shell, they are also one of the best-known groups in the fossil record. A rich and detailed picture of molluscan evolution is available to us as far back as the earliest Cambrian. But, of course, the further back in time we go the more questions we have about what the picture means. And it is in the earliest part of their history that the picture becomes the most opaque.

The Trenellidae are part of that early picture. This family of molluscs is known from the early Cambrian (Parkhaev 2002). They are part of the assemblage of early molluscs referred to as the helcionelloids, whose overall position in the molluscan family tree is very much open to question. Helcionelloids are simple, more or less cap-shaped or cone-shaped shells that are usually also tiny. The type species of the Trenellidae, Trenella bifrons, for instance, is only about 1 to 1.5 millimetres along the longest axis, and only one-half to one millimetre tall (Parkhaev 2001). This all adds up to a general shortage of morphological details that might help us pin down which, if any, modern molluscan groups helcionelloids are connected to. Possession of a undivided dorsal shell has lead many to compare them to gastropods. Others have pointed to the monoplacophorans like the modern Neopilina. In both cases, though, the resemblance is fairly superficial and confirming things one way or another would depend on identifying features of the soft anatomy, such as torsion, that are difficult if not impossible to infer from features of the shell alone.

Within the helcionelloids, trenellids are characterised by having the lower rim of one end of the shell's long axis drawn out into a siphonal groove. It seems likely that this groove was somehow involved in the passage of water around the gill(s), but whether its position indicates the front end or the back end of the shell, and whether it was used to draw water in or expel water out, depends again on what each author expects its original soft anatomy to have been. Unfortunately, evidence for the latter in trenellids is almost completely non-existent; while muscle scars have been identified in some helcionelloids, they remain unknown for this family.

The Trenellidae are closely related to, and probably include the ancestors of, the Yochelcionellidae in which the siphonal groove become raised and closed ventrally, turning it into a snorkel-like structure (one yochelcionellid, Yochelcionella daleki, has been featured on this site before). However, comparing trenellids to yochelcionellids raises something of a question in my mind. In general, mollusc shells grow through secretion from the mantle around the shell's rim only, meaning that once shell growth has passed a certain section the mollusc usually cannot go back and rearrange it. Assuming that helcionelloids grew in the usual molluscan manner, surely yochelcionellids would have gone through a stage in their development before the lower part of the 'snorkel' was closed off where they looked a heck of a lot like a trenellid? Is it even possible to distinguish a mature trenellid from a juvenile yochelcionellid?

REFERENCES

Parkhaev, P. Yu. 2001. Trenella bifrons: a new helcionelloid mollusk from the Lower Cambrian of South Australia. Paleontological Journal 35 (6): 585–588.

Parkhaev, P. Yu. 2002. Phylogenesis and the system of the Cambrian univalved mollusks. Paleontological Journal 36 (1): 25–36.

Lasiobelba: the Oppiid Way

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Lateral view (minus legs) of Lasiobelba pontica, from Vasiliu & Ivan (2011).


The animal illustrated above is a typical representative of Lasiobelba, a cosmopolitan genus of oribatid mites. Lasiobelba includes over thirty species of the family Oppiidae (Ermilov et al. 2014), commonly recognised as the most diverse family of oribatids. Oppiids are inhabitants of soils, where they primarily feed on fungi. Distinctive features of Lasiobelba within the Oppiidae include the absence of costulae (thickened ridges) on the prodorsum, and the presence of nine to ten pairs of setae on the notogaster that are inserted in two or four subparallel rows. The bothridial setae (the large sensory setae near the corners of the prodorsum) may be spindle-shaped at the ends or linearly hair-like; the two bothridial morphologies are used to distinguish two subgenera Lasiobelba and Antennoppia, respectively.

As is common for oribatids, there doesn't seem to be much information available for this genus beyond taxonomic studies. Lasiobelba species are most diverse in tropical and subtropical regions, with few reaching colder parts of the world. When they described the species L. pontica from the Movile Cave in Romania, Vasiliu & Ivan (2011) noted that this genus was otherwise unknown from the country. They suggested that this species might represent a relict of a warmer era that had managed to survive in the stable environment of the cave system after inclement conditions had driven it from the surface.

REFERENCES

Ermilov, S. G., U. Ya. Shtanchaeva, L. S. Subías & J. Martens. 2014. Two new species of oribatid mites of Lasiobelba (Acari, Oribatida, Oppiidae) from Nepal, including a key to all species of the genus. ZooKeys 424: 1–17.

Vasiliu, N. A., & O. Ivan. 2011. New oppiid species (Acari, Oribatida, Oppiidae) from Romanian caves. Trav. Inst. Spéol. "Émile Racovitza" 50: 3–14.

Crabs in Rivers, Crabs in Trees

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Freshwater crab Potamon ibericum, copyright Philipp Weigell.


Crabs are among the most recognisable animals one can find at the sea shore; any child who spends time at the beach will soon come to recognise their brandished pincers and sideways walk. But, as has been discussed by this site before, crabs are not only a coastal phenomenon. In warmer parts of the world, it may be possible to find crabs some distance inland.

Interestingly enough, there is at least circumstantial evidence that crabs made their way into fresh water relatively recently. The Old and New Worlds are each inhabited by a completely independent lineage of freshwater crabs that presumably originated after these continents went their separate ways. In the tropical Americas, rivers and streams are home to the Trichodactylidae, close relatives of the marine swimming crabs of the Portunidae. In the Old World, comparable habitats shelter a distinctly freshwater lineage comprising the superfamilies Gecarcinucoidea and Potamoidea.

Freshwater purple crab Insulamon palawanense, copyright Jolly Ibanez.


The classification of Old World freshwater crabs has (as with almost every other taxonomic group on this planet) shifted around a bit over the years. Many older references will combine all the Old World freshwater crab families into the Potamoidea but some more recent authors have tended to restrict this latter group to a single family, the Potamidae. There are other families, such as the African Potamonautidae and Deckeniidae, whose position superfamily-wise appears to be debated. The differences between the superfamilies Potamoidea and Gecarcinucoidea are primarily expressed in the structure of the males' second gonopods, the modified legs that the crabs use in transferring sperm during mating (Brandis & Sharma 2005). In the Gecarcinucoidea, a basal projection of the second gonopod surrounds the main body like a funnel for much of its length, while the tendril-like distal projection past this funnel is grooved and open on one side. In the Potamidae, the covering projection is restricted to the dorsal side only, and the distal part of the gonopod forms a closed tube.

Socotra limestone crab Socotra pseudocardisoma, copyright Gaëtan Rochez.


The Potamidae are most diverse in the Oriental bioregion with over seventy of the nearly eighty recognised genera being found there (Yeo et al. 2008). A couple of genera are found in the Afrotropical region. Only one genus, Potamon, makes it to Europe with modern species found in Italy and the Baltic peninsula, though the fossil record indicates a broader distribution on this continent in the past (Klaus & Gross 2009). Potamids are found in all types of water bodies, from fast-flowing streams and rivers to calm lakes and ponds, though they are inhabitants of the littoral zone rather than deep waters. The distinctive species Socotra pseudocardisoma is found on semi-arid limestone uplands of (surprisingly enough) the island of Socotra. Crabs of this species spend most of their time sheltered within cracks and crevices in the rocks that remain reasonably cool and damp year-round; they only emerge to the surface to forage during the rainy season while the surface briefly holds pools of standing water (Cumberlidge & Wranik 2002).

Another unusual lifestyle is found in a recently discovered species of the family Potamonautidae. This species from the Usambara Mountains of Tanzania specialises in living in phytotelmata, pools of water that accumulate in hollows in trees (Bayliss 2002). Though phytotelmata allow the crabs to inhabit regions of the rainforest that might otherwise be off limits, they are not the most forgiving of habitats. The combination of their small size together with an accumulation of organic matter means that the water in them tends to be quite acidic, a definite problem for a crab that relies on its calcitic exoskeleton for protection. The crabs feed on snails found in litter of the rainforest floor, and emerge from their home hollows to hunt at night or on cloudy, wet days. After eating a snail, they carry its shell back with them to their phytotelma and drop it in. The lime from the snail shell helps to neutralise the acidity of the water in the phytotelma, as well as supplying much-needed calcium that the crab will itself absorb when the time comes for it to moult to a new exoskeleton.

REFERENCES

Bayliss, J. 2002. The East Usambara tree-hole crab (Brachyura: Potamoidea: Potamonautidae)—a striking example of crustacean adaptation in closed canopy forest, Tanzania. African Journal of Ecology 40: 26–34.

Brandis, D., & S. Sharma. 2005. Taxonomic revision of the freshwater crab fauna of Nepal with description of a new species (Crustacea, Decapoda, Brachyura, Potamoidea and Gecarcinucoidea. Senckenbergiana Biologica 85 (1): 1–30.

Cumberlidge, N., & W. Wranik. 2002. A new genus and new species of freshwater crab (Potamoidea, Potamidae) from Socotra Island, Yemen. Journal of Natural History 36: 51–64.

Klaus, S., & M. Gross. 2009. Synopsis of the fossil freshwater crabs of Europe (Brachyura: Potamoidea: Potamidae). N. Jb. Geol. Paläont. Abh.

Yeo, D. C. J., P. K. L. Ng, N. Cumberlidge, C. Magalhães, S. R. Daniels & M. R. Campos. 2008. Global diversity of crabs (Crustacea: Decapoda: Brachyura) in freshwater. Hydrobiologia 595: 275–286.

Delta Wasp

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Two views of the potter wasp Delta unguiculata, copyright Entomart.


Not so long ago, I found myself struggling with the challenge of identifying potter wasps. Potter wasps are close relatives of the social wasps, close enough that they are usually classified in the same family Vespidae, but they belong to a distinct lineage (the subfamily Eumeninae) of a more solitary bent, each female constructing its own individual nests in which to lay its eggs. The 'potter' part of their name refers to their preferred material for said nests which are sculpted from mud. Though they do not form the vexatious swarms that social wasps can, potter wasps still tend to be relatively large and impressive wasps, and like social wasps they are usually strikingly patterned in bold colours to give fair warning of their potentially painful stings.

Nevertheless, despite being the sort of thing that would be likely to attract interest, identifying potter wasps can be a definite challenge. For a large part of the twentieth century, eumenine genera were mostly divided very finely, with the features separating related genera often difficult to distinguish. Here in Australia, I found an approachable identification guide for most eumenines to be nigh on nonexistent. One potter wasp genus that I did successfully pull out, however, was Delta.

Female Delta campaniforme constructing a nest, from Brisbane Insects.


Delta is a genus of about fifty species of potter wasp found in warm regions of the Old World. At least one member of the genus, D. campaniforme rendalli, has become established in Florida after being introduced there from southern Africa (Menke & Stange 1986). Delta belongs to the Eumenes group of genera, in which the first segment of the metasoma (the petiole) is very long and slender. Distinctive features of Delta within this group include the second segment of the metasoma being relatively short with the associated tergum bell-shaped, and the males having the last segment of the antenna bent backwards to form a hook (Nguyen 2015). Females build their mud nests, which they stock with moth caterpillars, cemented to flattened surfaces such as the sides of buildings or along branches. The species introduced to North America possibly arrived in the form of a nest glued to some easily transportable substrate such as a shipment of lumber.

The names of Delta and many other Eumenes-group genera derive from the work of Henri de Saussure, who recognised a single genus Eumenes corresponding to this group but divided it into a number of sections that he labelled Alpha, Beta and so forth. Later authors raised these sections to the status of separate genera though some expressed the objection that Saussure may have never intended these alphabetical designations to be formal names at all. The validity of Saussure's 'genus-group names' was eventually settled by a decision of the International Commission on Zoological Nomenclature but authors such as Menke & Stange (1986) have continued to criticise the recognition of these difficult segregate genera, especially as, whereas the Eumenes group as a whole is probably monophyletic, many of its component genera may not be. Future classifications may yet see Eumenes gathering its prodigals back into the fold.

REFERENCES

Menke, A. S., & L. A. Stange. 1986. Delta campaniforme rendalli (Bingham) and Zeta argillaceum (Linnaeus) established in southern Florida, and comments on generic discretion in Eumenes s. l. (Hymenoptera: Vespidae: Eumeninae). Florida Entomologist 69 (4): 697–702.

Nguyen, L. T. P. 2015. Taxonomic notes on the genus Delta de Saussure (Hymenoptera: Vespidae: Eumeninae) from Vietnam. Animal Systematics, Evolution and Diversity 31 (2): 95–100.