Lutz Thilo Wasserthal

The rôle of butterfly wings in regulation of body temperature

Abstract Free and unnarcotized butterflies in a vertical basking position were exposed to radiation from a halogen lamp. Warming rate and equilibrium excess temperatures were recorded by means of microthermistors on the cuticle. Living, dead, and dried specimens were irradiated partly and totally. If the wings are shaded, the excess body temperature is reduced by about 30 per cent. The major portion of the heat transferred from the wing to the body originates from 15 per cent of the wing surface nearest to the body. There is no significant difference in excess thoracic temperatures of living and freshly dead specimens. After drying, the body temperature level rises about 1·4 to 2·2°C, remaining almost constant between 15°C (not radiated) and 37°C (radiated). The influence of air convection was tested with dried specimens under varying spatial orientation, keeping incident radiation constant. In an approximately horizontal position the heat arising from the wing increases to about 40 per cent by accumulation of warm air under the wing base. The ecological implications of heat supply by the wings and adaptive significance of wing pattern are discussed with respect to different modes of heat transport

Oscillating haemolymph ‘circulation’ in the butterflyPapilio machaon L. revealed by contact thermography and photocell measurements

Summary1.Pulsing and streaming of haemolymph in the heart, aorta and perineural sinus of unrestrained, unnarcotizedPapilio machaon L. (Lepidoptera, Papilionidae) were studied. The interrelationships between heart activity, abdominal movements and activity of thoracic pulsatile organs in haemolymph transport were examined and the indirect effects of these activities on tracheal ventilation of the thorax evaluated.2.A thermistor technique was developed to record haemolymph movements by their convective and conductive cooling effects at the cuticular surface of insects. In addition, the direction of pulses and of haemolymph flow was determined from temperature measurements, utilizing the temperature gradient along the body axis of basking butterflies.3.The direction of heart peristalsis changes periodically and is coordinated with abdominal length changes which were recorded using a photocell. Abdominal expansion is accompanied first by a pause and subsequently by reverse beating of the heart. Abdominal expansion may play a leading role in backward haemolymph transport and cause periodic ventral haemolymph backflow through the perineural sinus. Such backflow is most vigorous during heart pauses. The rhythmic undulatory movements of the ventral diaphragm give rise to only slight thermal convective effects.4.The oscillation of haemolymph between thorax and abdomen is documented on the basis of changes in thermal conduction of the thorax. The significance of periodic haemolymph volume reduction in the thorax for tracheal ventilation is discussed with special regard to the role of heartbeat reversal.5.During the forward heart pulse periods the abdomen performs volleylike ventilatory movements. These do not cause streaming of haemolymph in the thoracic haemocoel, which at this time is shut off from the abdominal haemocoel by a valve mechanism. This valve, situated in the anterior abdomen, was examined histologically and by scanning electron microscopy.6.The activity of the lateral thoracic pulsatile organs is regularly interrupted by pauses which occur most frequently during the second half of the hearts forward pulse period. The function of the pulsatile organs is discussed in relation to changing thoracic haemolymph content.

Oscillating haemolymph ‘circulation’ and discontinuous tracheal ventilation in the giant silk mothAttacus atlas L.

Summary1.In the mothAttacus atlas (Saturniidae) an oscillating haemolymph ‘circulation’ and its coordination with tracheal ventilation are described. Periodic heartbeat reversal, intermittent backward haemolymph flow through the perineural sinus and two different superimposed modes of abdominal movements are analyzed by means of contact thermography and photocell measurements.2.Intraperiodic fluctuations and age dependent alterations in heartbeat frequency and duration of pulse periods are discussed with respect to changes in haemolymph volume and haemocoele capacity.3.The frontal aortal sac shows transport activity only during the forward pulse period of the heart; during the backward pulse period the amount of haemolymph in the head is reduced. The aorta continues to pulse in the freshly severed head.4.The expiratory air flow at the spiracles and spiracular valve closing were investigated. In the anterior part of the body expiration occurs slowly as a consequence of haemolymph accumulation during the forward pulse period of the heart, while inspiration takes place as a consequence of removal of haemolymph from the anterior body into the abdomen during a backward pulse period. When most haemolymph is accumulated in the abdomen, expiration of the abdominal tracheal system is accomplished by bouts of abdominal peristaltic movements. The latter are aided by coordinated closing of the abdominal spiracular valves.5.Transient haemolymph pressure increase by ventilatory movements is probably restricted to the abdomen by a septum and valve in the anterior abdomen. This compartmentation of the adult lepidopteran body combined with haemolymph oscillation is suggested to be a principle advantage in optimal utilization of a small haemolymph quantity with regard to tracheal ventilation in flight-adapted, light-weight construction.

Innervation of heart and alary muscles in Sphinx ligustri L. (Lepidoptera)

SummaryThe origin and orientation of the heart nerves in Sphinx ligustri and Ephestia kuehniella were investigated by scanning electron microscopy using a special technique which involved pinning the dissected specimens on a stabilizing metal pad. The heart and alary muscles in Sphinx particularly their caudal extremity were also examined by transmission electron microscopy. The alary muscles form an incomplete sheath around the heart with a mainly longitudinal fibre orientation, e.i. antagonistically to the fibres of the heart itself. The heart and alary muscles are multiterminally innervated by branches of the transverse segmental nerves. All branches contain a single electron lucent axon; the thickest branches also possess several neurosecretory axons. Swellings of the segmental nerves may indicate the position of nerve cell bodies. There are no lateral heart nerves. Only one type of neuromuscular junction is abundant in the alary muscles but less frequently found in the heart. The terminals originate from the central axon only. They are capped by glial cells, which interdigitate with the muscle cells. They penetrate into the T-system toward the Z-discs and form a complex intercellular space system. Exocytosis of dense-cored vesicles into this “perisynaptic reticulum” seems likely. Sites of neurohaemal release are distributed along the nerve branches and special nerve endings occur at the level of the ostia. The possible nervous influence upon heart activity is discussed.ZusammenfassungUrsprung und Verlauf der Herznerven bei Sphinx ligustri und Ephestia kuehniella wurden unter Verwendung von Präparationsunterlagen aus Bleiblech rasterelektronenmikroskopisch untersucht. Herz und Alarmuskeln von Sphinx ligustri wurden mit besonderer Berücksichtigung des caudalen Herzabschnitts im Transmissionselektronenmikroskop untersucht. Die Alarmuskeln bilden eine unvollständige Hülle um das Herz aus überwiegend längs orientierten Fasern, antagonistisch zum Faserverlauf im Herzmuskel. Herz und Alarmuskeln sind multiterminal über die transversalen Segmentalnerven innerviert, deren größte Zweige ein elektronentransparentes und mehrere neurosekretorische Axone enthalten. Verdickungen der Segmentalnerven enthalten möglicherweise Nervenzellen. Laterale Herznerven wurden nicht gefunden. Synaptische Axonendigungen nur eines Typs sind in den Alarmuskeln häufig, im Herzmuskel seltener. Sie werden nur von dem zentralen Axon aus gebildet. Die neuromuskulären Kontaktstellen sind von Gliazellen bedeckt, die über zahlreiche Ausläufer mit der Muskelzelle verzahnt sind und mit ihr ein “perisynaptisches Retikulum” bilden. Die Gliazellausläufer dringen in das T-System bis zu den Z-Banden vor. Exozytose von Neurosekret-Vesikeln in das perisynaptische Interzellularsystem wird angenommen. Neurohämale Abgabeorte finden sich entlang der Nervenäste und in speziellen Nervenendigungen auf der Höhe der Ostien. Der mögliche Einfluß der Innervierung auf die Herzaktivität wird diskutiert.

Ultrastructure of a scent scale organ with pressure discharge in male Caligo eurilochus brasiliensis (Fldr.) (Lepidoptera: Brassolidae)

SummaryThe abdominal scent apparatus of male Caligo eurilochus was examined at different ages by light, scanning and transmission electron microscopy. The glandular epithelium is covered with specialized scales and forms a pad on each side of the 4th to 6th abdominal segments. The pads are surrounded by smooth, elastic cuticle and can protrude toward the opposite hind wing hair pencil. The scales have a poreless cuticle with a fibrillar texture. They are impregnated by an oily, slowly volatile substance. The scales are elongated toward the base, forming hoods over the long coneshaped sockets. The scale pedicel is anchored tension-free by rootlets in the central socket base. The slightly asymmetric cuticular sockets are very elastic, due to their high water content. They are stabilized by internal epicuticular rods. The release of the secretions from the cell and a possibly active microvillar transport is discussed. Different secretions are found in the space between the microvillar surface of the gland cell and the socket floor. They are probably discharged from the supraglandular space into the scale lumen by means of pressure and bending of the sockets. A flowback might be prevented by capillary effect of a “ball” of vesicles, which lies exactly above the outlet of the scale pedicel.

Haemolymph flows in the wings of Pierid butterflies visualized by vital staining (Insecta, Lepidoptera)

SummaryThe flow of stained haemolymph was photographed in the wings of resting Pieris rapae, Pieris brassicae, and Gonepteryx rhamni under UV-radiation at definite intervals after abdominal application of fluorescent tetracycline. There is no circular route in the wing. All wing veins are supplied with stained haemolymph from their own bases without preference to single veins. In freely resting Pieris with intact wings, most veins are completely stained after 20 min. The staining pattern supports the existence of an oscillating haemolymph supply mechanism in the wing veins and shows that the cross vein and encircling sinus are not essential in the supply of the longitudinal veins. Inflow of stained haemolymph into the wing membrane begins about 1 h after application and is generally completed within 12 h in Pieris. The wing membrane is supplied with fluid by diffusion and — especially under low relative humidity — additionally by haemolymph substitution of evaporated water.This mechanism is associated with the disadvantages of water loss and probably salt withdrawal from the body. The puddling behaviour of butterflies might help in restoring these postulated deficits. It is hypothesized that haemolymph substitution of water evaporated from the wing membrane is a preadaptation for accumulation of defensive toxins and pheromones in the wing membranes, especially in diurnal and basking Lepidoptera.The veinal system of 5-day-old young summer specimens of Gonepteryx stains more intensely than that of 4–5-month-old specimens just before entering hibernation. The transition of stained haemolymph from vein to membrane is reduced in this species, probably as an adaptation for water retention during diapauses.

Multinucleate neurons with neurohaemal and synapsing axons at the heart and alary muscles of the butterfly Caligo beltrao Illiger (Lepidoptera)

SummaryThe segmental heart nerves of Caligo beltrao Illiger (Brassolidae) were examined by transmission and scanning electron microscopy. Heart and alary muscles are innervated by branching processes of single multinucleate neurons (MNNs). There is one MNN situated at each segmental fan-shaped group of alary muscles. The main nerve of the MNN consists of a bundle of processes. This nerve extends centripetally toward the CNS and corresponds to the dorsal portion of the transverse nerve. However, neither axo-somatic nor axo-axonic synapses were found, the presence of which might suggest that this nerve contains axons of different neuronal origin. The synaptic contacts of the MNN with axons originating from the CNS are therefore assumed to be established beyond the spiracular region.In addition to the neuro-muscular junctions of the smaller centrifugal axon branches there are neurohaemal release sites along the entire length of all MNN axon bundles. Axon terminals are packed with either dense-cored or multigranular vesicles. Both morphological types of vesicles are, however, found side by side in the large axons and in the perikaryon, often at the same Golgi element. These morphological findings may support the concept that more than one transmitter is produced in a single neuron. Questions that arise in reference to dual or polyfunctional neurons and to the control of cardiac activity are discussed.

Funktion und entwicklung der flügel der federmotten (Lepidoptera, Pterophoridae)

SummaryWing structure in Pterophorids with normal and lobed wings is analyzed with reference to resting and flight behaviour evoked by predator induced stimuli and related to the resting position of the wings, the modes of wing folding, wing marking and typical biotopes.The resting position and folding of the wings in Pterophorids are basically different from those in other moths, as is shown by comparison with Ephestia (Pyralidae) and a noctuid moth. Folding of the wings is a precondition for the development of the family-specific scent scales on the veins on the underside of the hind wings.On the basis of comparative morphology it seems likely that the structure of lobed wings derives from wing folding. The different venation of the plumate lobes indicates that folding has led to cleft wings on two independent occasions.Wing folding is more pronounced in species that live in sparsely vegetated areas. In species indigeneous to areas of abundant vegetation, forewings are generally no longer foldable. Folding of the hind wings, however, is always at least partly realized in these species, as a protection against volatility for the scent scale area. The absence of folding in the forewings is generally associated with conspicuous disruptive pattern. Adaptive coloration is strictly confined to parts that are exposed while the insect is in the resting position.The trend towards wing lobation has continued independently of signs of folding. Economy of material and energy is suggested as the main reason, as the investigation by Norberg (1972) has shown no special flight characteristics. There is no correlation between phyletic time of origin of lobes and depth of fissures.The Pterophorids are able to give different responses to mechanical stimuli according to mode and intensity; slight tactile stimuli evoke immediate flight, while agitation induces apparently passive immobility characterized in fact by active clinging and balancing.Outstretched wings and hindlegs combined with constant readiness to react to tactile stimuli characterize the Pterophorids as quick starters, while rolled or folded wings, concealment coloration and stubborn maintenance of the resting position characterize them as phytomimetic creatures. Thus their appearance can be interpreted as a compromise of protective adaptation evolved to avoid two different groups of predators - arthropods and birds. The development of lobed wings in the pterophorid plume moths can be assumed to be the result of a process influenced by several interacting selective factors.ZusammenfassungDer Flügelbau der spreiten- aund federflügeligen Pterophoriden wird dargestellt und im Hinblick auf das Ruhe- und Fluchtverhalten gegenüber typischen Feindreizen in Zusammenhang mit der Flügelhaltung, Flügel-Faltungstypen, Tracht und typischen Biotopen untersucht.Flügelruhehaltung und -faltung der Pterophoriden weichen grundsätzlich von der der übrigen Nachtfalter ab, wie ein Vergleich mit Ephestia (Pyralidae) und einer Noctuide darlegt. Die Flügelfaltung wird als Voraussetzung für die Herausbildung der familienspezifischen Duftschuppen auf den Adern der Hinterflügel-Unterseite angesehen.Die Struktur der Federflügel lät sich vergleichend morphologisch auf die Faltung zurückführen, die nach der unterschiedlichen Anordnung des Geäders zweimal unabhängig voneinander zur Aufspaltung der Flügel geführt hat.Die Flügelfaltung ist starker ausgeprägt bei Arten, die in schütterer Vegetation leben. Bei Arten aus dichterer Vegetation sind zumeist die Vorderflngel nicht mehr faltbar. Die Hinterflügel-Faltung wird dagegen nie ganz aufgegeben, wahrscheinlich wegen ihrer zusätzlichen Funktion als Verdunstungsschutz für den Drüsen-schuppenbereich. Fehlende Vorderflngel-Faltung ist in der Regel korreliert mit deutlicher optisch zergliedernder Zeichnung. Das Vorkommen einer “Sichtzeichnung” ist stets streng gebunden an die in der Ruhe exponierten Flächen.Unabhängig von Anzeichen einer Faltung hat sich der Trend der Federbildung weiterentwickelt. Die Ursache kann in Material- und Energieersparnis gesehen werden, nachdem die Untersuchung von Norberg (1972) keinerlei flugtechnische Anhaltspunkte ergeben hat. Spalttiefen and phylogenetisches Alter der Federbildung sind nicht korreliert.Die Pterophoriden sind in der Lage, mechanische Reize nach Art and Stärke unterschiedlich zu beantworten; sie reagieren auf leichte Beriihrungsreize mit sofortiger Flucht, auf Erschütterungen mit scheinbar passivem Sitzenbleiben, das durch Balancier- und Festhalteaktivitäten gekennzeichnet ist.Abstehende Flügel und Hinterbeine, gepaart mit stets vorhandener Fluchtbereitschaft bei Berührungsreizen, charakterisieren die Pterophoriden als Schnellstarter, eingerollte bzw. gefaltete Flügel, Tarnfärbung und “stures” Ruheverhalten bei Erschütterungen als phytomimetisch. Ihre Gestalt lät sich somit als Kompromi aus Schutzanpassungen gegenüber zweierlei Räubergruppen — Arthropoden bzw. Singvögeln — erklären. Die Entstehung der Federflügligkeit kann als Ergebnis eines Prozesses erklärt werden, der von mehreren ineinandergreifenden Selektionsfaktoren beeinflut wurde.

Generalisierende und metrische Analyse des primären Borstenmusters der Pterophoriden-Raupen (Lepidoptera)

The setal pattern of Pterophorid first larval stages is homologized to the hypothetical pattern of the Ditrysia ancestor; it is utilized to reconstruct the ancestral pattern of the three European subfamilies and to classify them genealogically. For infra- and interspecific analysis, the setal characters of Pterophorinae are discussed in combination with the morphologic characters of the genitalia, which for this purpose are presented in detail.