Ogyris genoveva (Hewitson)
Form splendida (Tindale)
This is a large magnificent Lycaenid. It is the largest conventionally blue coloured Lycaenid to be found in Australia, and some females can reach 6 cm measured across the open wings. (The brown coloured Liphyra brassolis is the largest Lycaenid, which is found in the tropics.)
The butterfly belongs to the compact O. genoveva-O. idmo Species Group of interesting Lycaenid butterflies within the Ogyrini Tribe having very similar morphology and which are closely associated with the large Camponotus sugar-ants. O. genoveva, along with O. zosine form the isolated O. genoveva Species Subgroup within this group, as these two species have very similar adult morphology and early stages. The latter flies in tropical to subtropical areas, and takes over in distribution where O. genoveva finishes. Some of the more specialised species of the group have larvae which are believed to be either predatory on the immature stages of these ants, or perhaps are fed by the ants at least when the larvae are very immature, which has allowed these species to overcome the adverse effects of the periodic loss of the hostplant, particularly from bush-fires, from which Ogyris genoveva suffers.
Like all Lycaenids, the adults are sexually dimorphic in morphology on the wing uppersides, and in this species the difference is very obvious. The males are purple coloured above, which can vary from pale to dark purple to indigo-purple, whereas the females have bright metallic blue uppersides with a large yellow patch in the apex of the forewing. In the females the metallic 'blue' colour varies from blue to greenish blue to bluish green. The extent of the blue areas is variable. In form genua the blue area is always restricted. In form splendida the blue area is extensive as shown in the above image. In the females the intensity of metallic green colour can also be influenced by exposure to moisture.
The distribution of O. genoveva is essentially continuous from southeast South Australia, through Victoria and NSW, into southeast Qld. The morphology of the adults is variable, particularly within the females, which seems to be phenotypic (environmentally or geographically) controlled, (possibly even a thermoregulation feature.) The variation is most obvious in the females, in the areal extent of the forewing yellow patch, the areal extent of the metallic blue upperside areas especially in the hindwing, and the degree to which the blue areas are greenish. Females from hot, dry inland areas tend to have extensive upperside 'blue' areas that are blue, whereas females from moist or cool coastal areas have reduced 'blue' areas that are greenish blue or bluish green.
The two adult morphological forms splendida and genua found in South Australia represent the respective extreme end forms of the phenotypic or geographic cline. (This does not mean for example that eggs of form splendida obtained from the Flinders Ranges and reared through to adult stage in the Fleurieu Peninsula will produce form genua, or vice versa, but that the two colour forms are an adaptation to their present habitat niche, and that there are morphological adult form intergradations between the two extreme forms in the intervening geographic space. The two end-point forms are in the process of speciation into two separate species, as has already happened in the evolutionary past to produce O. genoveva and O. zosine. ) In South Australia the form genua predominates in the Mt Lofty Range between the Fleurieu Peninsula in the south and Clare in the north. Females from the southern Fleurieu Peninsula have extremely reduced bluish green areas, whereas in females from Clare the 'blue' areas are bluish green or greenish blue and are more extensive. Females from Waikerie in the Riverland to the east of Clare have even more extensive 'blue' areas that are blue or greenish blue. Females from the hot Northern Flinders Ranges and Danggali areas are similar to those from Waikerie, except most of the butterflies have extensive blue coloured areas with many having the extreme colour form morphology of splendida. Interestingly, both female colour forms can occasionally occur in each (north and south) population, but the dominant form for each population is as mentioned above.
Within known colonies, the butterflies are often seen in flight, particularly during peak periods of emergence. The male butterflies have a very rapid flight, and are usually active about the tops of the tall Eucalyptus mistletoe host trees some 5-20 m above the ground (mistletoe is the larva foodplant), but also spend a lot of their time settled with wings closed on a bare branch or twig near the top of the tree. There they will wait for newly emerged females to show up for mating. These butterflies often become 'invisible' when settled, as like all other Ogyris species, they have cryptically marked undersides that make the butterflies indistinguishable from the rough bark of trees and bushes when they are settled. Sometimes they imitate a blackened dead leaf still attached to the bare twigs. Periodically however, the males will fly off to patrol an area by circling a few different trees harbouring the mistletoe hostplant in a given area, then settle again for a while before repeating the patrol exercise. There are often territorial battles between rival males seeking a prime perching position.
The males will also patrol or congregate on hilltops near the hostplant. In the Mt Lofty Range the males often simply congregate on the hilltops using the available trees as they would where the hostplant grows. In the Flinders Ranges males tend to include hilltops in their patrols, arriving every 20-30 minutes to check for the presence of newly emerged females, which they do by briefly circling the hilltop once or twice, and if no females are present then they continue on their patrol of the area. (Butterflies of many species use hilltops for mating purposes, particularly when either sex is in short supply. If either adult cannot find a mate near where they emerged from the pupa then they will fly to the nearest hilltop and settle and wait for an opposite sex companion to arrive to complete their courtship.)
The females are slower in flight (unless disturbed), and when not feeding on the flowers of the mistletoe or other nearby flowering vegetation, they spend much of their time searching for places to lay eggs. They spend a lot of time on the mistletoes walking all over the plant testing the stems (presumably for traces of ants) with their ovipositor. In peak season within a major colony, many butterflies can be seen flying around a given host tree bearing mistletoe hostplant. They tend to favour mistletoe host trees in open woodland rather than those in a more constricted habitat, and like most Ogyris they prefer smooth-bark Eucalyptus rather than box or stringy-bark types.
A pair of binoculars is usually necessary to get a close look at this butterfly, unless you stumble upon a female laying eggs on the trunk of the mistletoe host tree. The butterflies are often seen to fly with Ogyris olane about the tops of the host trees, as the larvae of both butterflies use the same mistletoe larval hostplant. These two butterflies are usually easy to differentiate due to their difference in size, with O. genoveva being much larger, or if you have a pair of binoculars then they can be differentiated by the hindwing tornal extension in O. genoveva which looks like a short stubby tail. This extension is absent in O. olane and other Ogyris likely to fly with O. genoveva on hilltops, such as Ogyris amaryllis.
The metallic blue colour of the females and other blue coloured Ogyris butterflies is affected by moisture, and if the blue wing scaling somehow gets wet, it irreversibly changes to green.
In South Australia, larvae have only been found on the mistletoes Amyema miquelii (box mistletoe) and A. pendula pendula (drooping mistletoe) (Loranthaceae). The larvae eat the flower buds, flowers, leaves and soft stem parts of the mistletoe, but are particularly fond of the flower buds. The mistletoes usually associate with Eucalyptus, although A. pendula will also parasitise Acacia melanoxylon, particularly in the Lower Southeast Region of the state (where the butterfly has yet to be found).
In the eastern states other mistletoes are also utilised as hostplants, and those that can be found in SA comprise Amyema miraculosa (fleshy mistletoe) and A. quandang (grey mistletoe).
Larvae found along the Mt Lofty Ranges (that generally equates to the distribution of form genua) are attended by numerous large sugar-ants Camponotus consobrinus. Elsewhere in South Australia (that generally equates to the distribution of form splendida), larvae are attended by numerous, very large sugar-ants Camponotus nigriceps. Both these ants prefer heavy loam soils, although the latter also build nests in tree hollows above the ground if the soil is sandy. A similar ant attendance preference is also apparently found elsewhere in Australia, with butterflies that occur in coastal and moist areas being mostly attended by C. consobrinus, whereas butterflies found in inland areas being usually attended by C. nigriceps. The very large and aggressive C. intrepidus is also an attendant ant in the eastern states, but this ant is not known to occur in South Australia.
The ants are nocturnal, large, only moderately ferocious (but without a sting), although C. nigriceps can sometimes be aggressive. They have formed a symbiotic relationship with the butterfly, whereby the ants provide protection to the early stages of the butterfly from predators and parasitoids, and in return the ants receive sugary secretions from the median dorsal secretionary organ (honey gland or Newcomer's organ) situated at the posterior end of the larvae. Adult ants are able to live off these secretions. Unlike the situation with Ogyris subterrestris in which adult butterflies are often killed by the ants on contact, Ogyris genoveva is not attacked unless it remains within the ant chamber after emergence from the pupa (if deformed or blocked in by other pupae). However, the butterflies often become agitated in the presence of the ants and will distance themselves from any unnecessary attention. (It only requires a bight from these large ants to inflict a mortal injury. )
The ants essentially farm the larvae. They build separate chambers away from the ant nest to house the larvae. The ant chambers or galleries are specially constructed below ground around the base of the host tree by the attendant ants for sheltering the early stages of this butterfly. There can be multiple entrances, but they are always narrow and easily guarded by the large Camponotus ants. These chambers can be quite extensive, circling the base of the tree and extending along parts of the roots. The gallery space between the tree and the ground is usually not much wider than the mature larvae or pupae. Sometimes larvae will use hollowed out branches that are lying on the ground next to the base of the host tree. Camponotus nigriceps will more often use hollows within the host tree for use as a gallery. These ant chambers are usually widely separate from the actual ants' nests (or ant brood), but sometimes butterfly larvae will occur near the nest, but in this situation the ants construct a separate chamber adjacent to the nest to house these larvae which is separate from the ant brood.
The ants provide 24-hour protection, and when the larvae leave the chamber at night to feed on the mistletoe, they are guarded non-stop until they return to the chamber again before dawn. The ants also keep the chamber clean of larvae frass (excrement) and moult skins. Studies have shown the incidence of larvae parasitisation, probably the main way the larvae are predated, are about 30% with C. consobrinus, but can be reduced to as low as 5% by the extremely aggressive C. intrepidus (Eastwood 1997).
C. consobrinus is a common, large, orange and black coloured ant, that frequently enters houses at night in urban areas, where it is known as the sugar-ant. It is totally harmless to humans, unless one is allergic to formic acid. It should not be confused with the large stinging and dangerous bull-ants, inch-ants or jumping ants. The latter group have highly visible, very large and long jaws projecting down from the head. In C. consobrinus the jaws are not readily visible. C. nigriceps is common in pastoral areas, and is a large, yellow and black coloured ant. It is strictly nocturnal.
Large, hemispherical shape, strongly flattened top and bottom, the sides are very finely reticulated in a hexagonal pattern, with each reticulation intersection having a small raised blunt projection, the facets on the top of the egg are smaller and these continue to the small-depressed micropylar area at the apex of the egg. The basal half of the egg is greyish white, the top half is mostly dark brown with a greyish white ring near the outer dorsal edge, and the micropylar area is greyish white. The eggs are typical for the species-group. Some eggs may be a washed out grey or white colour, and near larval emergence the egg can sometimes turn pale grey. The larva emerges from the egg at night by eating out the dark brown coloured (central) dorsal area. (The parasitic wasps, one per egg, emerge from the egg by eating out a smaller circular area in the dorso-lateral region.) Eggs hatch after 6 days in summer. (The parasites emerge after about 20 days).
Using their sensory organs, the females actively seek out mistletoe hostplants that already support existing early stage colonies of the butterfly and their Camponotus attendant ants. Their antennae and palps probably locate the ants and mistletoe, but their ovipositor also seems to be involved in the process of locating the correct place to lay eggs. In the Adelaide Hills the females are often seen on the mistletoes within a known colony, walking all over them, testing the stems with their ovipositor without actually laying eggs. Using their sensory organs they eventually make their way down the trunk of the mistletoe host tree following the larva/ant trails (between the ant chambers at the base of the tree and the mistletoe high up in the tree), to locate the attendant ant chambers, and then they will start to lay eggs in batches. These batches can vary from just a few eggs up to large collections of eggs, and 46 eggs have been recorded in one large batch. The eggs are usually laid adjacent to each other to a depth of one egg, but in large batches they can be stacked upon each other two or three deep. The batches are laid beneath bark or within cracks of the tree trunk, usually within two metres of the ant chambers, which may be within a hollow in the tree or in the ground at the base of the tree. Older females will also sometimes lay one or two exposed eggs on the larvae/ant trails on the host tree. The females will only lay where there is a strong residual smell of the attendant ants, and also prefer hostplant which is already being utilised by the early stages of the butterfly. They prefer host trees in which the mistletoe is not too high off the ground, for obvious beneficial reasons for the larvae. The C. consobrinus ants prefer trees which have some loose vegetal debris about their bases.
In major colonies, there is a large incidence of egg parasitisation, as the eggs are unprotected by the ants, and the parasitoid wasp is too small for the ants to regulate. In an ideal environment the egg parasitoid probably keeps the colony to reasonable size limits, as otherwise the larvae would likely build up to enormously large numbers that would quickly eat all its mistletoe hostplant and result in the demise of the colony. The downside is that if the colony is stressed, the wasps could actually cause the demise of the colony. During the 2003 flight season (a drought season), a single large colony tree in the Adelaide Hills was examined late in the season, and from 265 eggs examined and it was found that 147 eggs had hatched normally, while 100 eggs had been parasitised and 18 eggs had remained unhatched.
The first instar is long onisciform shaped, weakly scalloped laterally, initially purplish brown coloured with a greyish white perimeter, and a broad broken greyish white longitudinal dorsal line that terminates at abdominal segment 6. After eating the hostplant, the pale areas turn pale greyish yellow, and the pale broken dorsal line becomes a solid line. The anterior and posterior ends are dark brown. The posterior dorso-lateral organs are not developed. The head is large, smooth, yellowish brown, hidden beneath the body. There are long peripheral and dorsal setae (hairs), which are longer anteriorly and posteriorly. The dorsal setae terminate at abdominal segment 6. The peripheral setae are mostly white, with a few black setae at the posterior end. Dorsal setae occur in two pairs, one black pair being long and recurved, the other pair being white coloured, short, recumbent and directed to the rear, except on the sixth abdominal segment where both pairs of setae are black, long and recurved.
The newly hatched first instars are believed to make their way down the trunks from the egg batches to the base of the trees to the ant chambers where they are probably rounded up by the ants and herded in with the rest of the larvae. The young larvae are very mobile due to well-developed thoracic legs, and are quite capable of climbing the host tree with ease every evening. (The first instar is about 2 mm long when it hatches from the egg). However, as the first instars do not possess posterior dorso-lateral organs the ants do not show as much interest in them as they do with older larvae that possess these organs. First instar larvae eat by scouring the leaf or bud surface, but older larvae eat from the leaf edge or devour the entire bud.
Intermediate instars gradually lose the long setae, and they are also strongly scalloped laterally. From the second instar, the dorso-lateral organs are prominent at the posterior end. The second, third and fourth instars have a similar colour to the fifth instar, but are mostly purplish brown coloured with the pale yellow markings being less obvious.
The butterfly tends to occur in colonies, of variable size, with some old colonies that have not been interfered with, reaching half a hectare or more in areal extent, with most of the mistletoe bearing trees in the area having early stages of the butterfly. Due to past clearing and fragmentation of habitat, it can be many kilometres before another colony is encountered. However, females will disperse from the colonies and on occasions, solitary trees are found with early stages of the butterfly. Some large individual trees in a colony can harbour enormous groups of larvae and pupae, and there are eastern states records of 200 or more individuals. In South Australia the documented numbers are less than 100, usually much less. Colonies are prone to communal diseases like bacterial and virus infections, which are transmitted by all the chamber occupants, including the ants.
The final instar grows about 30-33 mm long, but larvae distended by parasites may reach 40 mm in length. They are mostly dull purplish brown coloured, with pale yellow dorsal chevron markings and other indistinct subdorsal markings, the chevrons on abdominal segment 6 are joined together to form a yellow triangular mark, the lateral and anterior extremities of the larvae are pale yellow, the prothoracic plate is dark grey with a yellow longitudinal dividing line, the anal plate is dark brown and yellow with a black longitudinal dividing line, and the spiracles are black. It is long onisciform shaped, with a thoracic dorsal furrow, the lateral edges are scalloped, the anterior and posterior areas are flattened, there are some short peripheral bristly hairs, and there are some short dorsal bristles on thoracic segment 3 and abdominal segments 1-6. The body is covered in dark coloured, minute secondary setae, which consist of a short simple pointed shaft set on a protuberant, angular and ridged base. The secondary setae impart a scabrous appearance to the larvae. The posterior dorso-lateral organs are well developed. The head is small, smooth, brown, hidden beneath the body.
Larvae feed only during the night, accompanied by large numbers of attendant ants. The ants usually become active before the larvae and numbers of them head towards the mistletoe to make sure the path is clear of any obvious larva predators, like spiders. The larvae begin to emerge from the ant chamber shortly after dusk. The early instar larvae are often the first to emerge from the chambers, and quickly head off for the mistletoe, which can be up to 20 m away, high up in the tree canopy (although it is usually much less). Older instars are often more timid and slower to get moving, as the least disturbance can disorientate them. Eventually, a large procession of larvae and protective ants head off for the mistletoe. Larvae leave a silken trial as they climb the host tree to the mistletoe, which is discernible under certain lighting conditions. They always follow the same trail every night. Larvae in attendance by ants continually extrude their white coloured, extendable posterior lateral (tentacular) organs, which emit pheromone chemicals that convey an attentive warning signal to the attendant ants (i.e. "make sure you are looking out for me" ). The ants are often seen to ride on the backs of the large larvae as they move about on the host tree. Presence of larvae on a hostplant is readily discernible by larval eat marks on the mistletoe leaves, and they feed independently on the mistletoe (not gregariously). Larvae usually feed on warm nights, and return to the ant chamber before dawn.
During the day the larvae hide from predators by remaining in the ant chambers. The ants actively guard the entrances to the chambers. Larval excrement (frass) and the discarded skins from the moulting larvae within the chambers are removed by the ants. In South Australia, larvae attended by the less aggressive C. consobrinus have a high incidence of larval parasitisation by small braconid wasps (Apanteles sp). Some 30 or more wasp larvae will parasitise within a single large O. genoveva larva, and all will exit at the same time then collect beneath the butterfly larva to pupate, creating a white silken mass of tiny wasp pupa-cases. The exiting of the wasp larvae paralyses the butterfly larva, but ants continue to attend the stricken larva, which will take a few days to eventually die. Interestingly, the ants do not attack either the exiting wasp larvae or the adult parasitoid wasps, so it is likely the latter two have pheromones that mimic those of the butterfly larvae and attendant ants.
Larvae seem to require six instars to fully develop, and records of seven instars are known. The larva period is variable, depending on the location, time of the year, and the condition of the hostplant. During winter, larval development is very slow, and essentially ceases once the average temperature drops below 15 C. Over the warmer months the colonies usually contain larvae at all stages of development although mature larvae occurring outside of the main flight period are likely to be parasitised.
Long cylindrical, rounded anteriorly and posteriorly, about 18-22 mm long, dark brown to blackish brown, with a few very short lateral hairs on the abdomen. The surface of the pupa bears a very fine reticulated pattern (similar to the eggs) that produces a scabrous appearance. The larvae are strongly attached to the silked substrate by anal hooks and a central girdle, usually to any non-earthen object or surface below ground level within the ant chamber, such as the bark of the host tree or rock or stick or vegetation caught up within the construction of the chamber, or if the colony is large, to the roots of the host tree. Sometimes the larvae will pupate within white ant hollowed stumps or fallen boughs next to the base of the host tree, or in the case of Camponotus nigriceps in hollowed boughs or cavities higher up in the tree trunk. Occasionally the larvae will pupate beneath loose bark near the entrance to the chamber either on the host tree or on the ground, but often these larvae are parasitised. The larvae pupate gregariously together, and sometimes very large numbers of pupae can occur.
The butterflies usually emerge during the morning, and expand and harden their wings either within the chamber entrance if it is large enough, or on the mistletoe host tree up to 2 m above the chamber entrance.The ants do not normally attack the butterflies during this stage, although the ants will eventually destroy butterflies that emerge deformed or are unable to exit the chamber for any reason. The empty pupa shells are also destroyed by the ants, or if they do not do it quickly enough then another pupating larva may remove it to make room for its own pupation.
Butterflies emerging from the pupae are not covered in large quantities of fluffy grey 'down', which is known to occur in many other Ogyris. (This down helps protect the butterfly from being attacked by over-zealous attendant ants, or even other small predators, while the butterfly is expanding and hardening its wings in readiness for first flight.) Since O. genoveva often expands its wings within the presence of the protective attendant ants (which will not bother the butterfly unless either become very agitated), there is apparently no need for the predator-repellent down.
The pupae are not known to audibly stridulate, although interestingly, the prepupae can stridulate, making a series of audible clicks, which are believed used as a means of communicating with the attendant ants.
The pupa period is highly variable, depending on the location and time of year. In the South Mt Lofty Range the pupa period is about 34-35 days in late spring, reducing to about 14-24 days in mid-summer and early autumn. In the Olary Ranges the pupa period is about 33-38 days in early spring.
The butterfly flies throughout the warmer months with records from September to early June. In hot northern areas there seems to be 3 flights starting in September-October, where the butterfly tends to start flying earlier and finish later in the season compared to southern areas. The main flight in cool, southern areas occurs in January and February to usually coincide with the flowering of the mistletoe hostplants, which are used for nectaring purposes by the adults. In captivity, a brood can be completed in 12 weeks over summer-early autumn in the South Mt Lofty Range, and this could theoretically account for a much smaller secondary autumn flight that is sometimes witnessed in certain populations, but as with most colonistic Lycaenids there is staggered larva development which could also lead to an autumn flight. In the South Mt Lofty Range most of the larvae resulting from eggs laid during summer continue to develop over winter to form next seasons flight. The butterfly over-winters as larvae.
The butterfly is presently known from the Mt Lofty, Flinders and Olary Ranges, and the Riverland areas of the state. Its hostplants are common in the Southeast Region, but the soil type is mostly white sand or ephemeral wetland in which the likely attendant C. consobrinus ants are unable to live. The butterfly also occurs in Vic, NSW and southeast Qld.
The habitat between the Flinders Ranges and Broken Hill/Mildura where the butterfly occurs is similar to the habitat between the Flinders Range and the Nullarbor Plain but the butterfly has yet to be seen west of the Flinders Ranges, even though many concerted efforts have been made to try and find it. The presumed absence of O. genoveva from that area is puzzling suggesting that either this species is a recent immigrant to SA from the eastern states and has yet to breach this western area of SA or that the region west of the Flinders Ranges has suffered a previous relatively recent climatic event (global warming) that has eliminated the species from the area.
The butterfly can occur in a variety of habitats, from moist cool temperate to hot and dry semi-arid conditions. It is not found in arid or alpine areas. Limiting factors to its range appear to be a requirement for an average annual minimum temperature between about 6 and 12 C. It is most frequently found in open (Eucalyptus) woodland, and will sometimes briefly venture into the outer urban environment. The obligate attendant ants are widespread.
The butterfly is usually rare in its occurrence, but widely distributed. It can sometimes be locally common where it is well established in undisturbed colonies.
The habitat along the Mt Lofty Range and in the Riverland has been extensively fragmented and destroyed by past clearing efforts. This habitat continues to be destroyed for small acre farms and urban expansion. Remaining habitat in the Mt Lofty Ranges is also subject to frequent bush fires. In urban areas its mistletoe hostplants are usually considered pests and often removed from their hosts. Elsewhere, the butterfly is not generally under threat except where the habitat is adjacent to farming communities and affected by poison spray drift during crop spraying activities, especially when the poison is applied by aerial means. Parts of its range within the Southern Flinders and Olary Ranges are within the prime breeding grounds for the plague locust and the butterfly would be decimated by any toxic spray programs adopted by the Locust Control Board (as happened in year 2000). Burrowing animals such as rabbits and echidnas have the potential to destroy larva colonies at the base of the host trees. Stressed colonies may also be terminally weakened by the collective actions of parasitoid wasps that attack both eggs and larvae, such that adult butterfly numbers become too low to effectively maintain the continuance of the colony.
Spraying activity should be carried out judiciously. In urban areas a public education process is required for the Amyema mistletoe. Healthy trees are able to support this mistletoe, and there is usually a self-induced balance between the tree host and the mistletoe. If there appears to be an imbalance then it should not be a problem to thin out some of the mistletoe. An active Ogyris colony will help keep the mistletoe pruned. Ideally, every landowner should carry out their own property survey for this magnificent butterfly, by checking for larvae on mistletoe bearing host trees during a warm evening. If the larvae are present, then measures can be put in place by the landowner to not disturb the colony. Actions that can destroy the larvae colony include, digging around the base of the host tree, removing the host tree or mistletoe, removing debris from around the base of the host tree, insecticide spraying and burning off. Digging into the colony exposes the early stage larvae and pupae to predators, particularly parasitoids and other ants such as Iridomyrmex spp, which will quickly destroy the colony. The attendant Camponotus ants cannot fully protect the early stages once the colony chamber has been opened.