THE NEW ZEALAND GLOWWORM by Rosalie Frederikson Waitomo Caves Museum Society Inc. P.O. Box 12 Waitomo Caves New Zealand Cover Photo is of Glowworm Lava and Threads Photo: Malcolm Wood @ l983 Reprinted 1984 TABLE OF CONTENTS INTRODUCTIOJ Page A feature of anyone's trip to Waitorco Caves is a visit to the Glowworm Caves, and in the Glowworm Grotto we feast Introduction i our eyes on a wondrous sight. The cavern roof is dotted Early Records of the New Zealand Glowworm 1 with thousands of tiny lights, each being produced by our Habitat 2 New Zealand glowworm. Life Cycle Our New Zealand glowworm is quite different to so-called 'glowworms' from other parts of the world. These others Egg are mainly luminous beetles which use their lights only Larva to attract the opposite sex. The New Zealand globworm by Pupa > coEtrast is the larval stage of a fly, X-d will use its Adult 6 light in different stages of the life cycle as a lure for focd as well as to attract a mate. Mating 8 The scientific name of the New Zealand gloxworm is Oviposition 9 Arachnocampa luminosa. It be1or.g~to the family MYCETO- The Nest and Fishing Lines I0 PHILIDAE or 'fungus gnats', most of which, as the name Feeding Behaviour 13 suggests, feed on fungus. 'Aracho' refers to the web it spins, 'campa' to its gnb-like qualities and 'lminosa' Bioluminescence 16 to the light it emits. This species is found only in Population Regulation 19 New Zealand, but it has three relatives within the genus Evolution 22 Arachnocampa from Australia. Of these, Arachnocampa tasmaniensis, from Tasmania, is the closest relative. Man and the New Zealand Glowworm 23 Two cther smaller species are known from the Australian (by Mr. D. Williams, Manager of iriaitomo Tourist mainlmd, Arachnocampa flava and Arachnocam~arichardsae. Caves) This booklet attempts to presert to the Waitomo Caves Glossary 27 visitor a gereral knowledge cf the New Zealand glowworm - including details of habitat, life cycle, snare, Bibliography 29 feeding behaviour and light. Acknowledgements 32 ISBN 0-908683-03-0 First EdLtion 1983 EARLY RECORDS OF THE NEW ZEALAND GLOWWORM The first record of the New Zealand glowworm was by Rev. A.G. Purchas in 1871. He had collected the female fly and larvae of "one or two1' species of luminous insect from mines on the Thames Goldfields. In 1886, E. Meyrick ot,served that this luminous larva I "h..... Arachnocarnpa flava appeared to be a predatory beetle larva. He stated that the light came from the back of its neck, and thought it would be carnivorous, feeding on minute insects caught in the slimy network of its 'web1. Meyrick postulated that this beetle larva might use its light to attract its l New 1 food. South Later in 1886, G.V. Hudson refuted the writings of Wales ,.... ,z Meyrick stating that the light came from a large sticky ...;g: . Arachnocam .... knob at its posterior end. Furthermore he thought there >/ richariEe was little doubt that its food consisted of decaying vegetable matter as he had never observed flies or gnats captured in the webs. Hudson also disagreed with Meyrick's assumed function of the light. As the light was not shown regularly, he thought the larva used it to escape from enemies, for "when disturbed they nearly al- ways gleamed very briliiar.tly for a few seconds, suddecly shutting off the light adretreating into the earth". He was also quite confident this larva bore no relation- Distribution of the genus Arachnocampa [after Kermode ) ship to any beetle fmilies, and was in fact a small 'gnat1 or fly. These early observations of the glowworm are very in- teresting when compared to what is now known about this creature. Meyrick was quite wrong about the positioning of the light and about the larva being from a beetle family. However his observatiors were correct on the feeding behaviour (carnivorous) and function of the light (prey attraction). Hudson, on the other hand, was ac- curate in describing the glowworm as the larva of a %all fly and stating the posterior position of its light. He was incorrect however, on his other statements - the glowworm is not vegetariar, and nor is its light a means -3- of escape. LIFE CYCLE In 1886, Osten-Sacken from Germany, assigned this insect Like that of most insects, the glowwon life cycle has to the family MYCETOPHILIDAE, but he was unsure about to four stages - egg, larva, pupa and fly - with the entire which genus it belonged. F.A.A. Skuse (sydney) in l890 cycle taking approximately ten to eleven months. In the named it as Bolitophila lucinosa. The Englishman, Glowworm Cave there is an underlying annual cycle with a F.W. Edwards, 1924, noted that some of its characters new generation starting in late winter/spring (August - were unlike those of the European Bolitophila which feed October) each year. However there is considerable over- on the interior of fungi, form no web, and pupate in the lap between each stage of development, with most stages ground. He considered that there were sufficient dis- being present throughout the year. tinctive characters to establish a new genus, Arachno- -cmDa. Sdwards chose this name because of the spider like nabit of the larva forming webs adusing them to catch insects (spiders are scientifically referred to as Jrumer autumn / winter spring kuj -;:-3;:;::ies) . 1 1 Adults (eggs) The preferred habitat of the glowworm must include the following five major factors: 1) A hunid atriosphere to prevent the glowworm from drying Pupae out. 2) A suitable hanging surface, such as the ceiling of a cave, from which the larva can suspend its fishing lines. j) A relatively still (windless) environment to prevent the long sticky threads from targling. 4) h adequate supply of small flying insects for food. 1 ! 3) Darkness, in order that the glowworm's light shows. JFMAMJ JASOND The combination of these factors means that the glowworm Seasonal frequency of stages in the glowworm g as a very specialised environmental requirement. Suit- life- cycle. able places exist in forests, tunnels and of course zaves, habitats in which the glowworm may be found a: throughout New Zealand. The glowworm egg is spherical, 0.75 millimetres in dia- meter. When first deposited the egg is crem in colour, but will change to either light brown or orange-re6 with- in a few hours. The eggs are sticky and adhere to the substrate - in caves they are deposited directly onto the walls. The 'incubation' period is 20 to 24 days. weight or size and this de2ends on the availability of Luminescence does not occur in the glowworm egg. At food; an extreme exanple being a glowworm in Ruakuri near hatching the larva splits the skin of the egg and crawls the rockfall which is about 18 months old. The 'annual' out. cycle starts in late winter/spring, so a plentiful supply of food for the larvae during this period may cause early pupation and adult emergence before the following spring. The larva is the only stage of the life cycle that feeds. The pupa is a transitory stage, and the adult has no mouth. This is why the larval stage is so long relative to the others. The larva has to store enough food re- serve to 'feed' the pupa, the adult, and if a female, the Larva emerging from the egg. (after Richards) eggs of the next generation. Larva: When newly hatched the larva or worn is very small - three to five millimetres long and 0.33 millimetres a- cross. The larva immed5ately commences the building of a nest and by letting down sticky threads and 'switching on' its light, is able to attract its first meal. It is hy2othesised that cmnibalism is quite inportant for the newly hatched glowworm, as very few insects are small Glowworm larva removed f mm its nest (after Richards enough for the tiny larva to handle. Other young larvae would be one of the few food sources of similar size. PUDa : Before pupation the larva shrinks and becomes opaque. It The larva grows over a period of several months, to reach removes some of its fishing lines leaving an encircling a length of 30 to 40 millimetres. It is not necessarily barrier of shorter condensed lines. This may act as a confined to its nest being able to move 20 to 30 centi- protective shield to the pupa with the clear space pre- metres, and if greatly disturbed may move several metres. venting the fly becoming entanglsd after it merges. The Movement is by waves of muscle contractions passing along larva suspends itself vertically by a long thread, in its body - like the movement of an earthworm. this circle of lines, to pupate. The suspensory cord, The only part of the larva that is hard is the head cap- formed from the larval nest and its supports, enends sule, much like a 'crash helmet'. As the larva grows its from the ceiling to a region of the thorax. 'helmet' becomes too small and has to be replaced by Sexual differentiation first becomes evident in the pupal moulting. During total larval development there are four stage. The female is larger and stouter than the male, moults, with each larva stage being referred to as an and it possesses txo prominent papillae at the end of its 'instar' - first instar (newly hatched) to fifth instar abdomen, which although present in the male, are smaller. (last stage before pupation). Larval development in The female pupae range from 15 to 18 millimetres in total takes eight to nine months, but with considerable length and the males from 12 to 14 millimetres.