John L. Eaton

Nervous system of the head and thorax of the adult tobacco hornworm, Manduca sexta (Lepidoptera: Sphingidae)

Abstract The nervous system of M. sexta is described and compared to that of A. polyphemus and other insects. The nervous system of M. sexta has not undergone the same degree of fusion as that of A. polyphemus and therefore more peripheral nerves arise from the ganglia of M. sexta than from the ganglia of A. polyphemus . The fields of innervation of the nerves in the 2 moths are, however, very similar. In addition, several fine nerves, not previously described in Lepidoptera, have also been found. These include the ocellar pedicels and associated nerves and several nerve branches in the thorax.

The evolving genre of electronic theses and dissertations

Electronic theses and dissertations (ETDs) are a unique genre that is emerging in part as a result of the work to build the Networked Digital Library of Theses and Dissertations (NDLTD). Virginia Tech began requiring ETDs January 1, 1997 and has since received over 1350. Quality has already improved and what one has learned is more broadly shared now due to the intense interest in ETDs. This is a flexible genre that will enhance digital libraries in part because over half contain color images or other multimedia, including audio, video, or VRML files. Due to free access, many have been downloaded thousands of times. As the NDLTD expands, tens of thousands of these will be created each year all over the globe and in the near future the NDLTD will broadly support multilingual and federated searching. This paper presents findings at Virginia Tech as a case study of shifting book-length works to electronic documents for the global digital library.

Spectral sensitivity of the ocelli of the adult cabbage looper moth,Trichoplusia ni

SummaryThe spectral sensitivity of the ocellus ofT. ni was studied by electrophysiological techniques. ERG waveform, amplitude-energy functions, spectral sensitivity obtained by criterion response methods and light adaptation experiments were used to study spectral mechanisms. Results indicate two spectral mechanisms with peak sensitivities at 360 and 530 nm. The data supporting two spectral mechanisms are differences in ERG waveform at short and long wavelengths, different slopes in amplitude-response functions at short and long wavelengths, the presence of two peaks in spectral sensitivity curves and the differential effects of UV and green adapting lights on the ocellar ERG response to UV and green stimuli.

Fine structure of the ocellus of the cabbage looper moth (Trichoplusia ni).

SummaryThe dorsal ocelli of adult cabbage looper moths were studied by light microscopy, and scanning and transmission electron microscopy. Each ocellus has a cuticular lens located on the distal end of a cuticular cone which encapsulates the receptor cells. There are two distinct types of receptor cells in the ocellus. Seventy large receptor cells form plate-like rhabdoms with several adjacent cells to produce a rhabdom network in the ocellus. Proximally ninety small receptor cells which have a disorganized microvillar rhabdomere are located at the base of the rhabdoms formed by the large cells. Extensive areas of gap junctions which occur between the rhabdoms and the membranes of large and small cells suggest that the cells may be electrically coupled to one another. Axons from both large and small receptor cells leave the base of the ocellus and extend to the protocerebrum to synapse with second order neurons.

Insect photoreceptor: an internal ocellus is present in sphinx moths.

Adult sphinx moths lack external ocelli. In Manduca sexta and other anocellate moths structures homologous to ocelli have been observed. Histological examination of such a structure in Manduca sexta has shown structural similarities to ocelli of other insects. Electrophysiological studies revealed a response to light stimuli stimilar to the electroretinogram of external ocelli. The evidence strongly suggests that the structures are internal ocelli.

Role of moth ocelli in timing flight initiation at dusk

ABSTRACT. The role of ocelli in timing flight initiation of cabbage looper moths, Trichoplusia ni (Hübner) (Noctuidae), at dusk was studied under simulated sunset conditions using a multichannel actograph. The mean time of flight initiation was determined for control, sham (sham/occluded, sham ablated, unilateral ablated) and experimental (ocellus occluded, ocellus ablated moths). Ocellus occlusion delayed flight initiation on the first day following treatment but was less effective on the subsequent days. Ocellus ablation also delayed flight initiation on the first day, and also produced pronounced delays on subsequent days. In studies where the sunset was advanced 1 h, control sham ocellus occluded and unilaterally ocellus ablated moths responded to the advance, but bilaterally ocellus ablated moths did not. These results indicate that moths make use of input from the ocelli in determining the threshold light intensity for flight and in making adjustments to small light‐phase changes.

Large ocellar interneurons in the brain of the cabbage looper mothTrichoplusia ni (Lepidoptera)

SummaryThe topography of ocellar interneurons in the brain of the cabbage looper moth,Trichoplusia ni, was examined with the use of the cobalt infiltration and Timms silver-sulfide intensification techniques. Two interneuron tracts are found in each half of the brain. One nerve tract is composed of 6–7 first order interneurons whose axons run to the ipsilateral side of the brain and terminate in the ventral protocerebrum. The other nerve tract is composed of 3 interneurons. Two of these are first order interneurons which project to the contralateral side of the brain where they terminate in the posterior protocerebrum. A third interneuron has processes connecting the two lateral ocelli and projects to both the ipsilateral and contralateral protocerebrum. Several small fibers are also present. Some of these extend to the lobula and the optic tubercule. A classification of ocellar interneurons for comparative study is proposed.

The Networked Digital Library of Theses and Dissertations: Changes in the University Community

DIGITAL LIBRARIES are one of the most effective vehicles for change in higher education. They facilitate collaboration involving universities in an international cooperative venture, unlocking scholarly resources, and carrying out functions previously limited to publishers. They allow faculty and students to improve learning by drawing on rapidly growing collections of valuable content—heretofore largely hidden behind the doors of the library—that include an increasing proportion of multimedia elements or interactive software.The Networked Digital Library of Theses and Dissertations (NDLTD), launched in 1996 and building upon work started in 1987, is a federated effort involving well over 120 universities scattered around the globe. Rapidly growing as a result of local, state, regional, national, and international efforts, it aims to enhance the skills of all graduate students preparing theses or dissertations, so they are empowered to create an electronic thesis or dissertation (ETD) and to effectively use digital libraries. As universities move to require submission of ETDs, they build the local infrastructure to support their own students in this regard and to dramatically enhance access to this important genre of scholarly publication. NDLTD supports these changes and helps ensure that the move to ETDs remains a sustainable initiative that will continue to enhance university libraries and publishing.

The internal ocellus of Manduca sexta: Electroretinogram and spectral sensitivity

Abstract The electroretinogram and spectral sensitivity of the internal ocelli of tobacco hornworm moths ( Manduca sexta ) were examined using extracellular electrophysiological techniques. The internal ocelli produce a cornea negative waveform when stimulated by light. Two spectral mechanisms (360 nm and 520 nm) were discerned on the basis of (1) different waveform characteristics at u.v. and visible wavelengths, (2) presence of two peaks in spectral sensitivity curves, and (3) selective adaptation by u.v. and visible wavelength stimuli. The ocelli are more sensitive to 520 nm than that to 360 nm light stimuli.

Synaptic organization of the cabbage looper moth ocellus

SummaryChemical and electronic synapses are present in the ocellar synaptic region of the moth, Trichoplusia ni. The chemical synapses all appear to be of the “conventional” type. Four different chemical synaptic contacts were observed: Receptor cell axons presynaptic to receptor cell axons, receptor cell axons presynaptic to 1st order interneurons, 1st order interneurons presynaptic to receptor cell axons, and 1st order interneurons presynaptic to 1st order interneurons. Two different types of contact made by electronic synapes were observed: Contacts between receptor cell axons and 1st order interneurons, and contacts between 1st order interneurons. The significance of this synaptic arrangement for the generation of “on” and “off” responses in the 1st order interneurons is discussed.