119.

LAND MOLLUSCS

MAYOR ISLAND

Ē.N. Milligan.

Collecting was from four localities on the island: 1) Leaf mould from valley immediately North of Opo Bay (= N. Opo). 2) Leaf mould and mossy stones in valley at North of Omapu Bay (= N.Omapu). 3) South-west rim of crater under pohutukawa (= S.W.crater) - high humidity as indicated by moss and fern flora. (1 and 3 collected by E. White and J. Fawcett. 4) Under Mingimingi (Leucopogon fasciculatum), East Crater (= E. crater). Collected by J. Edwards.

Sub-Class: STREPTQNEURA ORDER: SUB-ORDER: FAMILY: Aspidobranchia. Rhipidoglossa. Hydrocenidae.

Species: Hydrocena purchasi 494 - common crawling on moss. S.W. crater..

ORDER: SUB-ORDER: FAMILY: Pectinobranchia. Taenioglossa. Liareidae. Liarea egea 572 ~ common. S.W. crater.

FAMILY: Cyclophoridae. Murdochia pallidum 545 ~ 2 specimens. IT.Opo.

Sub-Class: EUTHYNEURA

ORDER: SUB-ORDER: TRIBE: FAMILY: Pulmonata Stylommatophora Holognatha Flammulinidae.

Allodisous dimorphus 1504 - N.Opo, 1 sp.; E.Crater, common. The latter specimens varied from the: type in having' more inflated whorls, lighter background colour and ... more conspicuously patterned, and were more closely ribbed. Serpho,kivi 1526 - Common, N.Opo, S.W.Crater, E. Crater. Therasia decidua 1532 - Common, S.W. Crater.

Therasiella . tamora 1534 - .Qnei specimen5r K. Omapu. Fiammulina n.sp. cf. Chiron - Not uncommon, S.W.Crater, "~ (riblets, where regular, 6 per mm.) 120.

Flammulina perdita 1557 - 1 sp., N.Omapu; Common, S.W.Crater.

FAMILY: Charopidae. Ptychodon tau 1564 - Common, N.Opo, N.Omapu, S.W.Crater.

Laomidae. Laoma poecilosticta 1635 -2 specimens, N.Opo. Phrixgnathus conella 1644 - 1 sp. , S.W.Crater. P. fulguratus 164'8 - 1 sp. , N. Omapu. P. glabriascuius 1660 - Common, N. Omapu.

FAMILY: F";-;^ i^atidae. Tornat.ellinops novoseelandica 1687 - Uncommon, S.Wr.Crater.

TRIBE: FAMILY: Agnatha. Paryphantidae. Delos coresia 1735 - fairly common, N. Opo. D. jeffreysiana 1736 - Common, N.Opo and N.Omapu,

Little collecting was dc,;..3 - 18 species were collected bnt from this collection one new specie, in the genus Flammulina. was found and also an atypical population of Allodiscus • dimorphus. This would indicate that speciation may be more exten• sive on the island and further collecting may be more fruitful. Moat of the molluscs found are of general distribution and some, I e.g. Therasia decidua. T^aoma poecilosticta and Phrixgnathus glabri- | as cuius, are well known' for their migratory abili tie's from studies on other islands. However, the recording of the somewhat localised ; Tornatellinops is of interest.

LAND MOLLUSCS

"OF HEN IS L A N D

E.N. Milligan.

Collecting was limited to a section from Old Woman's Cbve north to the central ridge of the Island. Apart from small areas along the coast' and on the broader parts of the dividing ridge, the ground was of loose, unstable andesitic rubble. The steep slopes, often covered with the fern Asplenium lamprophyllum, had a low water retention and were not suitable for "the high humidity requirements of most molluscs. On the less steep slopes this sub- 121.

stratum supported large numbers of one species (Suteria ide) which was found covering the ground in numbers of 4-6 per sq. metre. In small water courses with some accumulation of leaf mould a limited number of species were found.. • These were more frequent on the broader parts of the central ridge..., This area was covered by Leptospermum ericoides with abundant undergrowth. A constantly high ground humidity was indicated by the presence of Paryphanta busbyi which has little resistance to desiccation. In an area of not more than 2,000 sq. yds. 21 species of 14 genera and 5 families were found. Only one of the species (Tornatellinops novo- seelandica) found elsewhere on the island was not found here.. This was collected by the. stream at the camp site; and along with Rhytida tarangaensis and Ptychodon tau v/as the only record from the restricted area of coastal flat. Rhytida tarangaensis, a species autochthonous and indigenous to the island, was an item of interest. An extensive search was made among fallen nikau fronds in a large nikau grove on a flat area some hundred yards to the west of the camp site and in a smaller grove up the campstream valley. In three and a half hours? collecting 6 live specimens were found. As many again were found dead, the shells characteristically chewed by rats: the native rat was common, nesting in nikau debris. Amongst richly humus covered andesite stones on the dividing ridge this species was more common - 4 live specimens and a few dead ones taken in less than an hour. G. Hard found this species common in the same habitat along the ridge to the east.

Sub-class: STREPTQNEURA ORDER: SUB-ORDER: FAMILY: Pectinobranchia. T a enlog1o ssa. Liareidae.

hla.EEB.^S.E^L 5^2 ~ not uncommon.

Sub-class: EUTHYNEURA. ORDER: SUB-ORDER: TRIBE:- FAMILY: Pulmonata Stylcmmatophora Holognatha Fi^mmulinidae

Serphq kivl 1526 - common. Therasia decidua 1532 - common. T. tamora 1534 - common- Flammulina perdita 1557 - common, F. feredayi? 1553 - common in rotting logs.

F AMTT.V.

Ptychodon tau 1564 ~ commo' P. pseudoleioda 1574 - un' Egestula egesta 1594 - u~ 122.

FAMILY: Laomidae. Laoma poecilosticta 1635 - uncommon. Phrixgnathus mariae 1639 - 1 juvenile spec. P. ariel 1642 - 1 spec. P. fulguratus 1648 - uncommon. Phrixgnathus glabriuscuius 1660 - common. P. phrynia? 1667 - 1 specimen. Paralaoma lateumbilicata 1 680 - uncommon.

FAMILY: Elasmatinidae. Tornatellinops novoseelandica 1687 - 2 specimens.

TRIBE: FAMILY: Agnatha Paryphantidae Rhytida tarangaensis 1693. Paryphanta busbyi 1701 - 2 dead specimens. Delos coresia 1735 - common. D. Jeffreysiana 1736 - common.

Most of the species listed are widespread in distribution but some of more limited range are useful records in distribution studies. Some records extend the range given in Suter?s Manual of New Zealand Mollusca considerably but as this was compiled before 1913 this is not surprising. Unfortunately no later distribution data has been collated, although mainland records are fairly good. The following list may have some interest: Flammulina feredayi - northern limit Hunua Ranges. ' Phrixgnathus phrynia - Chicken Is. - Hokianga to Sth Is. Paralaoma lateumbilicata - Chicken Is., Little Barrier etc. Tornatellinops novoseelandica - Whangarei Heads to Thames. The most interesting and valuable records are those of Rhytida jbarangaensis and Paryphanta busbyi. These snails are extremely poorly adapted to low humidity and the lime coated: eggs have no resistance to desiccation so that chances of migration other than by land are very unlikely. As R. tarangaensis is an autochthonous species it cannot have been introduced by human agency. This would appear to supply good evidence that Hen Is. has in some past time been attached to the mainland. The mainland species R. dunniae and R. forsythi have a lower spire in proportion to the • ~ " ^>nd the Poor Knights species R. , •-ies appear to have evolved from ntly have first become isolated / d from each other. 123.

MOLLUSC SPECIES LIST

OF LITTLE BARRIER IS.

E.N. Milligan and J.J. Sumich.

Sub-class: STREPTQNEURA.

RHIPIDOGLOSSA: „ n . , Hydrocenidae. .

•:'Hydrocena purchasi 494 - Common on ferns, Hingaia (Coll. J.Edwards)

PECTINOBRANCHIA: „ . , Cyc1ophoridae. ^Murdochia cytora 540 - one spec., Nikau debris, head ofWaipawa. *"!"M. pallid-a:, 545 - 1 spec. Awaroa Stream. Abundant in leaf mould. Karaka, Macropiper etc., Hingaia, Whekau, Awaroa etc. Li.reidae. "'^TJiarea carl.ne11 a 571 - Leaf mould, Hingaia and Awaroa - uncommon. Liarea turricuj_ata 574 - common in leaf mould. Haowhenua, Te Wairere and Hingaia.

Sub-class: EUTHYNEURA. FULMONATA: ..- . • F xammulinida e. * Thai as s ohel iir. zelaridiae 1500 - Soil, under rocks, nikau fronds. Hingaia, Whekau, and Awaroa - common.. »Allodisous planulatus 1 51j2 - 1 spec. Awaroa (Coll. E.N.M.) (gaia. »'!~A. urquharti 1517 -• Uncommon, leaf mould,' head of Waipawa Stm & Hin- i: + * Serpho kivi 1526 - Nikau fronds, Te Wairere, Te Waikohare, Awaroa 9 Whekau and Hingaia, uncommon. *:+ Therasie 11 a ce1incle 15,31 - Not uncommon, beech humus,. Thumb Track, Waipawa and above Hingaia. *+3i-J_ān^P-ā ^ 534 - Uncommon, Waipawa and Hingaia. * &ecidua 1.532 - Common in mould or crawling on forest floor, coastal and Thumb Track. '• ^+Phenacohelix ponsonbyi 1538 - Abundant, coastal nikau groves'& Thumb-,-' * Sut.eria...icle...1545 - Common in fallen nikau fronds and forest debris. •* Fl ammul ina chi r on 1547 - 1 spec, nikau, Whekau; 1 spec,-flax 1800' Thumb Track. feredayi 1553 - Uncommon, Summit Track & Hingaia.. * F« perdita 1557 ~ Coastal leaf mould, Hingaia., uncommon. * I?-pi I sbr 1559 - 1 spec, flax, 2100 ft.. Thumb Track. Otoconchidae. "'"Qtoconcha dimidiata 1489 - 1 spec. Cyathea debris, Waipawa. 124.

Charopidae. •fPtychodon tau? 1564 - 4 riblets/mm. on all but last whorl which has 8. Bifid lamella on body whorl, 1 spec. Thumb Track. +P. hectori 1569 - 1 spec..., moss, Summit Track; 1 spec, nikau debris, Haowhenua. hCharopa coma 1588 - Common,leaf mould & soil under rocks. (Fectola colensoi 1603 - Recorded by Adams, not found on trip.) * F. roseveari 1610 - 1 spec., soil under rocks, Hingaia.(J.Edwards) fcF. sp.cf. sterkiana 1611 - approx. 22 riblets/mm., v. low spiral, 2 spec, on moss, Summit Track. (J. Fawcett) '* F. (Subfectola) caputspinulae 1615 - Uncommon, leaf mould, Hingaia,

Laomidae. {4~Laoma jbeimonias 1630 - Not uncommon, leaf mould, Waipawa. +L. pirongiaensis 1634 - Abundant, esp. in beech leaf mould, Thumb Track and Waipawa Valley. L. poecilosticta 1635 - 3 spec, leaf mould under rocks, Hingaia. -+Phrixgnathus roariae 1-639 - 2 epee. Nikau debris, 1200 ft., Thumb Track soil under rock, Hingaia. > "P. allachroidus? 1640 - Beech debris, Thumb Track. Not uncommon. *+P. ariel 1642~~ 1 spec, leaf mould in kauri, 480', Thumb Track. +P. cheesemani 1643 - 1 spec. Haowhenua, 1 spec. Waipawa. P. conella 1644 - Uncommon, nikau leaves, Hingaia; ferns, Hingaia under rock; Muehlenbeckia, Westlanding. +P. sublucidus? 1649 - Beech debris, Thumb Track, not uncommon. +P. erigone 16)58 - Not uncommon, nikau debris, Waipawa. +3=P. glabriascuius 1660 - Common, nikau; .uncommon in leaf mould. North Titoki Pt., Waipawa, Hingaia. ^P. microreticulatus 1665 - 1 spec, on moss, Summit Track (J.Fawcett) +Paralaoma lateumbilicata 1680 - Coastal bush between Waipawa and Haowhenua.

Paryphantidae. 58 Delos coresia 1735 - Coastal leaf mould, 2 spec. (J.Edwards). * D. Jeffreysiana 1736 - Damp leaf mould above Hingaia, near Kauri Knoll and in Kauri Gulley, 3 spec.

Athoracophoridae. *+Athoracophorus bitentaculatus rufovenosus 1739 - 1 spec, Astelia; base of n**kau sheaths, Hingaia, Whekau and Te Waikohare,Common. *Vomanus marmorQus 1740 - Common in nikau bases.

Coll. by J. Sumich et al - May 1952. + Coll. by E.N. Milligan - August 1954. Coll. by J. Fawcett and E. White - July 1953 125. Dis>cussion

E.N. Milligan.

A fairly full list has been prepared for half of the periphery of the island, on the limited coastal flat and up some of the valleys. Limited collecting was done towards the In• terior of the island; J. Sumich found snails rare on the kauri knoll and Thumb track and the writer found them Inconspicuous on the Thumb track. This is possibly due to the drier conditions existing on the ridges especially under kauri (Messrs. "White and Fawce.tt found snails not uncommon in the moss and lichens of the Summit track). Only by collecting Beech humus for later sorting were large numbers of small species found, Fhrixgnathus pirongiaensis being particularly abundant. However a conspicuous mollusc creeping over the forest floor in kauri forest was Therasia decidua- one of our most hardy native species. The most striking fact about the list is its size - 42 species and subspecies. It seems likely that the collect- Ion was fairly complete. This figure presents an interesting con• trast with 33 for the larger and more intensively collected Stewart Is. (Dell, 1954). A comparison can be made with the list of 22 r species and subspecies from Hen Is., considering that the latter has probably been connected to the mainland. Unfortunately no numerical comparison can be made with the incomplete total of 18 from Mayor Is. The large land molluscan fauna of Little Barrier might suggest a land connection with the mainland, but until a comprehensive species list has been compiled from Great Barrier it is futile to make further comment along this line. One exception to this is the absence of the larger Paryphantic . , notably Rhytida and Schizoglossa. Rhytida occurs on the mainland surrounding the gulf; and on Hen, Waiheke" Great Barrier, Cuvier and East Islands. Schizo- glosjsa occurs less commonly around the gulf and on Great Barrier. These genera are well known for their intolerance to low humidity as they have lost the function of secreting a mucous plug. Their eggs are also extremely sensitive to dry conditions and these factors plus their large size makes them unlikely passengers on birds- or acciden•

tally in Maori canoes. Thi"s3 larger Paryphantid genera have consider• able value in indicating the possible presence of land connections and have been used for this purpose as supporting evidence for land bridges between the North and South Islands (Powell), It would appear then, that the absence of Rhytida and Schizoglossa may be a significant one, as one of the criteria for postulation of land connections is tha-.. all species ad• aptable to the land connected will migrate there readily (G.G.Simpson). On examining the list of land molluscs from these offshore islands one may consider the following points: 1) Does the fauna owe its origin to a land connection? If not, 2) Are the species common, hardy, and widespread in their distrib• ution so that they are likely to be colonisers of such islands purely by chance. 3) Have the species been carried by human agency? With respect to 126.

this point it is worth considering that Maoris commonly trans• planted plants, e.g. karaka and flax, to their various pas. (Graham), It Is believed that it is by this method that Placo- stlyus has been distributed to offshore islands (Powell). 4)Is there some mechanism (probably passive) by which land snails are readily carried to offshore islands? It has been suggested with respect to the sub-antarctic islands, e.g. Solander Is., Antipodes Is., that birds may be responsible for this (Dell,1954) On considering the three Islands, Mayor, Hen and Little Barrier, it can be seen that probably each island has re• ceived its population by several different means. As Paryphantids have proved reliable indicators of land connections it is a reasonable assumption that Hen Is. has been connected with the mainland sub- recently. As speciation has occurred on Mayor Is., it has probably been populated to some extent before human habitation. All contingencies are possible in studying Little Barrier. The verification of the absence of Rhytida and Schizoglossa may provide some concrete evidence. There is as yet no evidence of speciation on Little Barrier so that colonisation by human means cannot be ruled out. The occurrence of species with dis• junct distributions, e.g. Phrixgnathus pirongiaensis- is even more difficult to explain. This applies also, to a lesser extent, to Mayor Is. Little Barrier is well populated with sea birds, e.g. petrels, and perhaps this may be an important factor. The many small leaf mould specimens are the most likely species to be transported by this means. Apart from this type there occurs on the island the

operculate Liarea, the hardy Therasia decidua9 the arboreal Serpho ki'vi and the two slugs Qtoconcha and Athoracophorus. The first three specimens are among the most likely to survive a trip on a drifting log but the migration of the two slugs by this means or by birds de• fies imagination. This leaves for them Maoris or land connection. It seems then, for this island, it is as yet impossible to come to any decision, but .some facts have come out as pointers in a determination of the origin of the.local land molluscan fauna;. .

References:

Powell, A.W.B. 1932-53. The Paryphantidae of New Zealand. Var• ious papers. Rec. Auckl. Inst. & Mus. 1938. The Genera Placostylus in New Zealand. Vol. 2. Ibid. Simpson, G-. G-. 1953. Evolution and Geography; an essay on historical biology.

Suter, H, 1913. Manual of the New Zealand M0llusca Vtf'ith (1915) Atlas of Plates.