Using Insect Electroantennogram Sensors on Autonomous Robots for Olfactory Searches

Robots designed to track chemical leaks in hazardous industrial facilities¹ or explosive traces in landmine fields² face the same problem as insects foraging for food or searching for mates³: the olfactory search is constrained by the physics of turbulent transport⁴. The concentration landscape of wind borne odors is discontinuous and consists of sporadically located patches. A pre-requisite to olfactory search is that intermittent odor patches are detected. Because of its high speed and sensitivity^5-6, the olfactory organ of insects provides a unique opportunity for detection. Insect antennae have been used in the past to detect not only sex pheromones⁷ but also chemicals that are relevant to humans, e.g., volatile compounds emanating from cancer cells⁸ or toxic and illicit substances^9-11. We describe here a protocol for using insect antennae on autonomous robots and present a proof of concept for tracking odor plumes to their source. The global response of olfactory neurons is recorded in situ in the form of electroantennograms (EAGs). Our experimental design, based on a whole insect preparation, allows stable recordings within a working day. In comparison, EAGs on excised antennae have a lifetime of 2 hr. A custom hardware/software interface was developed between the EAG electrodes and a robot. The measurement system resolves individual odor patches up to 10 Hz, which exceeds the time scale of artificial chemical sensors¹². The efficiency of EAG sensors for olfactory searches is further demonstrated in driving the robot toward a source of pheromone. By using identical olfactory stimuli and sensors as in real animals, our robotic platform provides a direct means for testing biological hypotheses about olfactory coding and search strategies¹³. It may also prove beneficial for detecting other odorants of interests by combining EAGs from different insect species in a bioelectronic nose configuration¹⁴ or using nanostructured gas sensors that mimic insect antennae¹⁵.     

Group-Specific Multiplex PCR Detection Systems for the Identification of Flying Insect Prey

The applicability of species-specific primers to study feeding interactions is restricted to those ecosystems where the targeted prey species occur. Therefore, group-specific primer pairs, targeting higher taxonomic levels, are often desired to investigate interactions in a range of habitats that do not share the same species but the same groups of prey. Such primers are also valuable to study the diet of generalist predators when next generation sequencing approaches cannot be applied beneficially. Moreover, due to the large range of prey consumed by generalists, it is impossible to investigate the breadth of their diet with species-specific primers, even if multiplexing them. However, only few group-specific primers are available to date and important groups of prey such as flying insects have rarely been targeted. Our aim was to fill this gap and develop group-specific primers suitable to detect and identify the DNA of common taxa of flying insects. The primers were combined in two multiplex PCR systems, which allow a time- and cost-effective screening of samples for DNA of the dipteran subsection Calyptratae (including Anthomyiidae, Calliphoridae, Muscidae), other common dipteran families (Phoridae, Syrphidae, Bibionidae, Chironomidae, Sciaridae, Tipulidae), three orders of flying insects (Hymenoptera, Lepidoptera, Plecoptera) and coniferous aphids within the genus Cinara. The two PCR assays were highly specific and sensitive and their suitability to detect prey was confirmed by testing field-collected dietary samples from arthropods and vertebrates. The PCR assays presented here allow targeting prey at higher taxonomic levels such as family or order and therefore improve our ability to assess (trophic) interactions with flying insects in terrestrial and aquatic habitats.     

Inexpensive Laboratory-Constructed Nephelometer

An inexpensive, simple-to-construct nephelometer which was used to monitor the lysis of spheroplasts is described. The nephelometer is a flow-through device with a linear response to cell concentration from the lower detection limit to 8 × 10⁸ cells per ml.     

Inexpensive low-oxygen incubators

Although the evidence is overwhelming that ambient oxygen is at least somewhat damaging to most normal cells in culture, the expense and effort involved has resulted in few laboratories growing their cells under physiological oxygen conditions. We here describe how to produce, from commercially available plastic wide-mouth jars, very simple gas-tight containers that can be flushed with prepared gas mixtures to produce low-oxygen environments for standard cell culture. This permits any laboratory to easily try the effects of physiological oxygen on their system without the need for dedicated incubators and substantial monetary investments.     

Spiders Use Airborne Cues to Respond to Flying Insect Predators by Building Orb-Web with Fewer Silk Thread and Larger Silk Decorations

Orb-web spiders are an important group of trap-building animals that feed upon an array of insect prey and are themselves the prey of wasps and parasitoid flies. The purpose of this study was to examine whether spiders use airborne vibration cues to respond to these flying insect predators by changing their web-building behavior. While on its web waiting for prey, the orb-web spider Eriophora sagana was exposed to a vibrating tuning fork that emitted an airborne vibration signal. The signal mimicked the approach of flying insect predators and its effect on the subsequent web building was examined. No stimulus was provided during web building. A significant treatment effect was observed with respect to the total thread length (TTL) and area of the silk decoration (conspicuous white structure attached to the orb-webs of diurnal spiders) of their webs. While control spiders increased the TTL in their second web, the stimulus group spiders did not, providing the first evidence that orb-web spiders use airborne vibration cues to assess the predation risk and change their foraging activity. It also indicates that spiders remember an encounter with a predator on their webs and use this information later to adjust their web building. My findings imply that spiders devote less effort to foraging (i.e. web building) in response to the presence of their predators, which is considered to reduce their foraging efficiency. In contrast, the stimulus group spiders increased the area of their silk decoration significantly more in their second webs than did the control spiders. This is considered an experimental support for the hypothesis that silk decorations have an anti-predator function.     

Studies on Insect Growth Regulating Substances with Insect Cell Cultures

The sensitivity of cultured insect cells to a moulting hormone depended on their origin. Cell proliferation of cell-line C6/36, which originated from an Aedes albopictus larva, was suppressed by high concentrations of 20-hydroxyecdysone but was greatly promoted by low concentrations. Similar phenomena were observed with extracts of cedar and pine pollen. By employing the C6/36 cell-line for the screening of insect growth regulating substances, a highly active cell-growth promoting substance was found in a bovine pancreas extract. When 1 ppt of the partially purified substance was added to 2.5% fetal calf serum, the growth of cells was so greatly promoted that it was more than equal to that in the standard medium containing 10% of the serum.     

An Inexpensive Inverted Microscope System

An inexpensive and easily constructable inverted microscope system is described in detail. Its multiple experimental usefulness in many branches of biology is mentioned.     

植物的虫瘿与成瘿昆虫

虫瘿是植物组织遭受昆虫取食或产卵的刺激后,细胞加速分裂和异常分化而长成的畸形瘤状物或突起,它们是昆虫生活的"房子".介绍了虫瘿的形态多样性和形成过程,成瘿昆虫的多样性、生活史、寄生、食性和寄食现象,成瘿昆虫与寄主植物的关系以及人类对虫瘿的利用.     

Inexpensive precision temperature control for microculture

The design and construction of an inexpensive precision temperature control system used successfully for microculture applications is described. It is easily assembled from a homemade, precise, solid-state, proportional thermoregulator, resistive heating element, and insulated enclosure. The basic system easily adapts and can be customized for a variety of microculture applications with changes in enclosure dimensions or design. Control temperature accuracy, range and span can be varied by changing the components and design of the thermoregulator and enclosure. A series of such systems placed in a refrigerated or air-conditioned area accomodates multiple, parallel temperature treatments for experiments.Illinois Agricultural Experiment Station Projects No. 65-353 and 65-363. Supported in part by the Fred Gloeckner Foundation.