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Blue shining fungus gnats (Diptera) had been long reported in the Waitomo caves of New Zealand (Arachnocampa luminosa Skuse), in stream banks of the American Appalachian Mountains (Orfelia fultoni Fisher) in 1939 and in true spore eating Eurasiatic Keroplatus Bosc species. This current report observes that similar blue light emitting gnat larvae also occur nearby the Betary river in the buffer zone of High Ribeira River State Park (PETAR) in the Atlantic Forest of Brazil, where the larvae were found when on fallen branches or trunks enveloped in their own secreted silk. The new species is named Neoceroplatus betaryiensis nov. sp. (Diptera: Keroplatidae: Keroplatinae: Keroplatini) based on a morphological analysis. Neoceroplatus betaryiensis nov. sp. larvae emit blue bioluminescence that can be seen from their last abdominal segment and from two photophores located laterally on the first thoracic segment. When touched, the larvae can actively stop its luminescence, which returns when it is no longer being agitated. The in vitro bioluminescence spectrum of N. betaryiensis nov. sp. peaks at 472 nm, and cross-reactivity of hot and cold extracts with the luciferin-luciferase from Orfelia fultoni indicate significant similarity in both enzyme and substrate of the two species, and that the bioluminescence system in the subfamily Keroplatinae is conserved.

Bioluminescence in Diptera is found in the family Keroplatidae, in the glowworms of the genera Arachnocampa, Orfelia and Keroplatus. Despite belonging to the same family, Arachnocampa spp. and Orfelia fultoni display morphologically and biochemically distinct bioluminescence systems: Arachnocampa spp. produce light by the terminal ends of Malpighian tubules using ATP, a luciferin and a luciferase, whereas Orfelia fultoni produces light by translucent areas associated with rows of black bodies in the anterior and posterior parts of the body, using a 140 kDa luciferase and a luciferin which do not cross-react with the Arachnocampa luciferin–luciferase system, and a substrate binding fraction (SBF) which apparently releases luciferin in the presence of reductants. While several other keroplatids are not luminescent, we recently discovered a non-luminescent web-constructing keroplatid larva living in the roofs of caves in the Atlantic rainforest in Brazil, which noteworthily has a compound with Orfelia luciferin-like activity and its associated binding protein (SBF). Both the Neoditomyia luciferin-like compound and SBF cross-react with purified Orfelia luciferase to produce light in the same blue region of the Orfelia luciferin–luciferase system (479 nm). We also checked for the presence of Orfelia-type luciferin in Arachnocampa luminosa and Aedes aegytpi larval bodies, but no traces were found. Molecular studies indicate that Neoditomyia sp. is phylogenetically closer to Keroplatus and Orfelia than to Arachnocampa species. The presence of luciferin and its associated binding protein in this non-bioluminescent keroplatid larva indicates that luciferin may display another important biochemical function in keroplatid larvae and suggests that bioluminescence could be a recently evolved trait in Keroplatidae.

Larvae of the weakly blue-luminescent fungus gnat Keroplatus nipponicus possess on either side of their heads a small black stemmatal eye with a plano-convex lens approximately 25 μm in diameter. In total, 12-14 retinula cells give rise to a centrally fused rhabdom of up to 8 μm in diameter. The rhabdom's constituent microvilli, approximately 70 nm in width, are roughly orthogonally oriented, a requirement for polarization sensitivity. Screening pigment granules are abundant in the retinula cells and measure at least 1 μm in diameter. In comparison with the stemmatal eye of the brightly luminescent Arachnocampa luminosa, that of K. nipponicus is considerably smaller with a poorer developed lens and a rhabdom that is less voluminous, but possesses wider microvilli. Although the larval eye of K. nipponicus can be expected to be functional, as the larvae react to light with a behavioural response, the eyes are probably mainly involved in the detection of ambient light levels and not, as in A. luminosa, also in responding to the luminescence of nearby conspecifics.

The hypothesis that bioluminescence produced by larvae of the New Zealand glow-worm, Arachnocampa luminosa, attracts prey was tested experimentally in Reserve Cave, Waitomo, New Zealand, and in its bush-clad entrance over a total of 200 days during winter, spring, and summer. We compared catches on transparent adhesive traps placed either over glowworms or over areas from which glowworms had been removed. Adhesive traps over glowworms caught significantly more invertebrates per trap per day than did control traps. Glowworms in bush attracted greater numbers and types of invertebrates than did glowworms in the cave. Diptera predominated in both bush (86% of the total catch) and cave (89%). Also caught were small numbers of Araneae, Coleoptera, Hymenoptera, Orthoptera, Trichoptera, Gastropoda, Acarina, and Neuroptera—listed in order of abundance—but no adults of A. luminosa were caught. Glowworms under adhesive traps survived with little or no food for up to 78 days.

The swollen distal tips of the Malpighian tubules of the glow-worm Arachnocampa luminosa constitute the light organ. The ventral and lateral surfaces are covered by a tracheal ‘reflector’ and the nervous supply to the light organ comes from the ganglion in the penultimate segment. Fine nerve terminals, axons, and glial cells can be seen in close proximity to the basal surface of the cells of the light organ. The epithelial cells of the light organ are large, the cytoplasm dense, homogeneous and acidophilic. The cytoplasm gives a strong positive reaction for protein. The cytoplasm contains a high density of free ribosomes, patches of dense material, smooth endoplasmic reticulum, glycogen and scattered microtubules. Mitochondria are numerous; they are large, randomly distributed and packed with fine cristae. These cells lack the features characteristic of Malpighian tubule epithelial cells; infolding of the apical and basal cell surfaces is reduced and the cytoplasm contains few organelles. These cells do not contain secretory or photocyte granules and the grainy cell matrix is thought to be the luciferin substrate. Oxygen is supplied via the tracheal layer (which may have secondary reflecting properties) and light production controlled by neurosecretory excitation either directly via synapses, or by hormones. There are no other reports of Malpighian tubules of insects producing light and the fine structure of these cells is distinct. Thus, the swollen distal tips of the Malpighian tubules of the glow-worm undoubtedly constitute a unique luminescent organ.

Two entomopathogenic species of the hyphomycete genus Tolypocladium are described in detail. Tolypocladium extinguens sp. nov. was found on larvae of Arachnocampa luminosa (Diptera; Mycetophilidae) in caves in New Zealand. Tolypocladium cylindrosporum W. Gams is shown to be pathogenic to Aedes sierrensis and A. australis and is reported from Plecia nearctica (Diptera; Bibionidae). The occurrence of entomopathogenic species in this normally soil-borne genus is discussed.

The Malpighian tubules of the glow-worm are divided into four morphologically distinct regions, each composed of a different cell type. Part 3 of the Malpighian tubules of A. luminosa is intimately bound to the rectum by a layer of fat body. This association of the tubules with the hindgut is referred to as a cryptonephric system. This type of arrangement has been described in some Coleoptera and the larvae of most Lepidoptera but has never before been reported in the Diptera. In the glow-worm the cryptonephric tubules themselves are small, and adjacent to the fat body the epithelial cells are modified to form very thin windows or ‘leptophragmata’ (Lison, 1937). The main epithelial cells exhibit features characteristic of highly active, secretory Malpighian tubule cells. The high density of mitochondria and their association with all the microvilli is indicative of a highly active secretory cell. The high concentration of glycogen in these cells and their intimate association with the hindgut suggest that they may, in addition, have a nutrient absorptive function. The role of the cryptonephric rectal complex in the glow-worm is discussed in the light of present knowledge gained from previous studies of coleopteran and larval lepidopteran cryptonephric systems. On structural grounds a model is proposed for the regulation of the ionic environment of the rectum, and the uptake and metabolism of organic material from the rectal lumen by this cryptonephric complex.

Both larval and adult New Zealand cave glowworms exhibit reactions to light; their photoreceptors must, therefore, be regarded as functional. The two principal stemmata of the larva possess large biconvex lenses and voluminous rhabdoms. Approximately 12 retinula cells are present. In light-adapted larvae the diameter of the rhabdom is 8 μm and that of an individual microvillus is 49.5 nm. Dark-adapted eyes have rhabdoms that measure 14 μm in cross section and microvilli with an average diameter of 54 nm. The compound eye of the adult comprises approximately 750 ommatidia, each with a facet diameter of 27–28 μm. A facet is surrounded by 1–6 interommatidial hairs which are up to 30 μm long. The interommatidial angle is 5.5°. Cones, consisting of 4 crystalline cone cells, are of the ‘acone’ type. Pigment granules in the primary pigment cells are twice as large as those of the retinula cells which measure 0.6–0.75 μm in diameter. The rhabdom is basically of the dipteran type, i.e. six open peripheral rhabdomeres surround 2 central rhabdomers arranged in a tandem position. The microvilli of cells 1–6 and cell 8 have diameters ranging from 68 to 73 nm, but those of the distally-located central rhabdomere 7 are 20% larger. This is irrespective of whether the eye is dark or light-adapted. In the latter the cones are long and narrow, the screening pigment granules closely surround the rhabdomeres, and the rhabdom is less voluminous than that of the dark-adapted eye.

Isoenzyme analysis of 11 isolates of Tolypocladium cylindrosporum and T. extinguens revealed considerable variability between strains of the same species and confirmed great differences between the two species. An exception was the striking similarities in isoenzyme patterns observed for the California isolates of T. cylindrosporum isolated from Aedes sierrensis larvae from 1972 to 1979. This considerable homogeneity suggests a rather stable genotypic equilibrium in the fungal population which was maintained with little alteration even after repeated subculturing in the laboratory.