The following modifications in form and habits occur in B. luminosa: in the larva, the transformation of the distal ends of the malpighian tubes into light organs; the transformation of posterior tracheal lines into a hollow shell of tracheoles to form a reflector; elongation and further development of the gastric diverticula which, however, occur in other Mycetophilidae. The predaceous habit is known in several other members of this family. The vertical fishing lines appear to be unique to this species of Bolitophila (see back, Goldschimdt), the snares of other predaceous species resembling horizontal spider webs. In B. luminosa, the mucus droplets are placed on the vertical lines; in other species they are found where the web lines cross one another. Scolophore organs will probably be found in the other predaceous species with anal papillae (or gills) when they are examined more carefully. The pupal suspensory cord may be unique in B. luminosa.. The adult insect appears outwardly normal for the Mycetophilidae, lummosity being an extra modification of those malpighian tubules which possibly exist in the same position in other nearly related mycetophilid adults. The reduction of the bolitophilid larval antennae occurs in other forms such as Ceroplatus.. The mouthparts closely resemble those of the latter genus (see Edwards).

It is interesting to note that there are at least 100 species of Mycetophilidae already recorded in New Zealand, of which B. luminosa alone has been studied in detail.

Some fungivorous mycetophilids have a silken net on the pabulum. The predaceous habit thereby probably developed, and after that the ability to produce light to attract more food. Ceroplatus testaceous glows from its fat body, Bolitophila from its malpighian tubes. On any theory of Organic Evolution it is difficult to see how these different steps took place; but in any case no new organ has been developed for the production of lummescence, silk, or mucus in addition to what other Mycetophilidae are known already to possess.

The writer agrees with Goldschmidt that the Darwinian theory of small selected variations does not explain this or similar situations in animal life. The carnivorous habit, the snare building, lummosity, and the ability to cope instinctively with various situations are all remarkable developments in an insect whose ancestral types were all fungivorous, or spent their lives boring through and eating decayed vegetable matter. But it is equally difficult to understand how all the psychological and anatomical peculiarities of this animal came together at the right moment and at the right degree of development to make it what we know it to be today.

Probably the most remarkable anatomical development in B. luminosa is the tracheal boat which forms the reflector. This device could have been derived from fat bodies as it is supposed to be in coleopterous fireflies, but the New Zealand glow-worm combines in one modification both reflector and air supply. In the coleopterous fireflies there are separate modifications for this. The other noteworthy modification in the New Zealand insect is psychological. The capacity for instinctive reactions has developed in a remarkable way, yet anatomically it has a conventional hexapod nervous system. How far the size of its brain compares with that of a mycetophilid larva which spends its life boring in a mushroom is not known to the present writer. Psychologically, the coleopterous firefly's behaviour is uninteresting compared with the complicated nervous reactions found in B. luminosa. It is this combination of anatomical and psychological developments in the New Zealand glow-worm which are of importance to those interested in Organic Evolution. There is yet no satisfactory answer to the problem.

Regarding experiments on control of luminescence, the lighting up of the cut and separated last segment containing the light organs is interesting. The isolated segment will light up continually for two days and nights if kept damp. The individual tubes of the light organ continue luminescent when teased and separated

Not all cells luminesce, a patchwork of lighted and unlighted parts sometimes being noted.

There is a definite lag during the fade-out of the dousing light, likewise in the evening, the light comes on slowly. Glow-worms placed in the dark during the day light up after an hour or so. A flash lamp light turned on luminescent larvae at night causes slow dousing, the light starting again in the dark after about a-half hour or less according to how long the flash was on them.

The experiments reported earlier in this paper appear to show that the ganglion in the seventh segment controls the light, but not directly. It seems possible that nerves going to the tracheal reflector in some way cut off the supply of air, but neither such nerves nor valves in the reflector are known for certain. These larvae do not possess a biological clock, perception of light and darkness being usually the ultimate controlling factor. But the larvae do not always turn on their light, all larvae remaining doused on certain nights. There appear to be no careful observations on weather conditions and dousing, except for a few remarks by Hudson who did not go into this systematically. The experiments on the possibility of a “dousing hormone” failed; the lighted up pieces of the organ remaining luminescent when bathed in blood from a doused larva.

In the beetle Luciola, the flashing of the light at intervals ceases if the animal's head is cut off, but it can be induced to flash again if the cut end of the nerve cord is stimulated. This is the reverse of what happens in Bolitophora, where separation of the light organ from the body and therefore from the central nervous system, allows glowing to continue.

The nature of the pink granules in the longest region of the malpighian tubes is not known. They are probably urates, not lime. B. luminosa is the only insect known in which the malpighian tubes produce light, but in various other insects, silk has been described as arising from modified parts of these tubes. It is true to say, however, that the malpighian tubes throughout the orders of Insecta remain remarkably unmodified physiologically.

It has been noted that the light flashes brilliantly when larvae are dropped into Carnoy's fluid (absolute alcohol, chloroform and glacial acetic acid). This has not been followed up.

The snare presents some interesting problems. The vertical fishing lines depicted in Text-fig. 1 could obviously be made by the larva fastening one end to the side threads (S) and pulling out a silk thread covered with mucus. But the vertical lines in cave glow-worms' snares are up to two feet in length, and it is not known if these are let down from the runway and subsequently fixed at one time. Regarding the question of the manner of spinning of the vertical threads of the snare, various larvae have been observed holding the thread in their mouth as it is spun and lowered. Later, the thread, when long enough, was fixed in position by the larva.

The following are the known facts about the life cycle of B. luminosa: Pupae have been found on banks in late September and early March. Many larvae from November to March have imaginal discs. Larvae of all sizes were found from September to March, small ones predominating at Arapuni from February to March. At Waitomo, a pupa was found in February; it contained a number of ripe eggs. From these observations it appears that adults can emerge at any time during the summer.

A larva has been kept for six weeks, and fed on houseflies. It has recently pupated and the suspensory thread was not the original runway of the snare, but was specially spun after the runway and neighbouring sticky vertical lines had been cleared away by the larva. This silken thread began to darken within two days of pupation. It is possible that existent shorter lines are cut and a new piece added and the new end fixed to the runway. How the larva recovers prey from such long

fishing lines is not known, but recently a captive glow-worm was seen to climb down the vertical lines to suck out the contents of a fly put out of reach of its runway. The larva seems such a master in the manipulation of silk and mucus that it might be able to climb down and pull up the prey. It has been suggested that the larva pulls up the relevant fishing lines and so recovers the prey.

It has been mentioned by past observers, and it has been noted by the writer, that in many cases the larvae living in holes in banks have their snares almost completely screened by spider webs. It seems that in such cases the glow-worms must live on crawling prey which can get under the spider webs.

The success of the larva in living in different situations, especially in and banks, is due to its ability for water conservation. The cuticle is extremely tough and impermeable, and the mouth and anal openings small. The animal needs to conserve water to produce the mucus droplets. There must be few other insects which chop up their prey and swallow it entirely. Nothing is wasted. In many situations the capture of prey must be a longed-for event, upon which the growth and life of the larva depends.

On January 23, a new visit was made to Arapuni. The glow-worms tended to be in groups up to fifty in number, twenty being common, all of the same stage of development, as if the eggs had been laid by one female. Many of the groups were formed of very small larvae, their bodies being difficult to see, but the light they showed was bright. None of these young specimens had vertical fishing lines; all had an elongate runway like a narrow silk and mucus smear in the bank. In cases where this could be tested, these small larvae had a hiding place. Judging from the Arapum larvae, the elaborate curtam of fishing lines is only produced by larger larvae, and the newly hatched larvae must begin life by either finding or boring a suitable hiding place, then secreting a runway ending in the hole.

Once again observations were made on the possibility of noises affecting the larvae. These experiments showed that ordinary noises did not alarm the larvae. But the Arapuni larvae appeared more sensitive to the light from the flash-lamp than those in Wellington. When one approached a group, the light of the lamp caused many of them soon to fade out their lights. Some of the larvae also began to move towards their hiding places. However, return to the spot in about a quarter of an hour showed that confidence had been restored, and the lights were on again.

Some of the larvae were very small, and care had to be taken in removing them. If they became broken at their end, the light continued, and if gently crushed on the back of the hand, the luminescent organs appeared as a glowing smear. Mr. K. Carey, who had often visited this locality, informed the writer that on some nights no glow-worms showed their lights. No explanation of this was forthcoming. In the Wellington Botanical Gardens some larvae turn on their light sooner than others.

Since we now know that the female can lay up to about 80 eggs, the potential increase in population of the caves could be tremendous, unless kept down by predators or cannibalism—probably by the latter and starvation. But it is well to mention that of many larvae examined, not one was found with an empty mesenteron. They may, however, retain chitinous fragments in their gut till the next meal comes along and so give a false idea of prosperity. The beginning of life of the newly hatched larvae must be a difficult period. At this time they do not seem to exist in a non-predaceous manner. In any case, the eggs are large and yolky, and this must give them a start.

The impression gained is that according to food supply, the larvae may or may not grow slowly, that they can survive during winter, that they often wander from their territory as a result of which cannibalism takes place, and that they have no