Onion (Allium cepa L.) Attracts Scoliid Wasps by Means of Generalist Floral Volatiles.

Onion flowers require pollinator-mediated cross-pollination. However, the cues that pollinators use to locate the flowers are not well understood. The floral scent, along with floral visual cues, might acts as important signal to pollinators in order to locate the floral resources. We used electrophysiological methods combined with behavioural assays to determine which compounds in a floral scent are more attractive and thus biologically important to foraging scollid wasps. The majority of the molecules identified as floral fragrances in onions are common compounds that are already known from other angiosperms, and onion floral scents were predominately composed of aromatic components. The antennae of scoliid wasps responded to a large number of compounds, among them o-cymene, cis-ß-ocimene, benzaldehyde and allo-ocimene were behaviourally active. In contrast to other wasp flowers investigated nectar analysis demonstrated the dominance of hexose sugars over sucrose. Our findings provide fresh insights into the floral volatile chemistry of a key vegetable crop grown around the world. We demonstrate here that onion is using generalist floral volatiles to attract floral visitors. This insight could be utilised to make onion blooms more attractive to minor pollinators as well as major pollinators in order to maximise seed set.

Electrophysiological and Behavioral Responses of Spotted Stem Borer, Chilo partellus, to Sex Pheromone Components and Their Blends.

The spotted stem borer, Chilo partellus (Lepidoptera: Crambidae) is the major insect pest of maize and sorghum crops during the rainy season. The pheromone released by adult virgin females has been reported to consist of (Z)-11-hexadecenal (Z11-16:Ald) as major component and (Z)-11-hexadecenol (Z11-16OH) as minor component. The latter has been reported to reduce the efficiency of major component to trap the male moths. We studied the electrophysiological and behavioral response of male C. partellus moths to Z11-16:Ald, Z11-16OH, their E-isomers (E)-11-hexadecenal and (E)-11-hexadecen-1-ol, and blends. Electroantennogram (EAG) studies revealed that male C. partellus antennae elicited significantly greater responses to both (Z)-11-hexadecenal and (Z)-11-hexadecenol compared to their respective E-isomers. Behavioral response studies through wind tunnel and cage bioassay showed that blends of Z11-16:Ald and Z11-16OH in the proportion of 100:100 and 100:95 elicited significantly higher responses from male moths. The attractiveness of these pheromone components and blends in field also revealed that traps baited with 100:100 proportion was most effective. Our studies clearly showed that the minor alcohol component Z11-16OH is important for enhancing attractiveness of the pheromone and provides a more effective blend for monitoring of this pest.

Odour Cues from Fruit Arils of Artocarpus heterophyllus Attract both Sexes of Oriental Fruit Flies.

The Oriental fruit fly, Bactrocera dorsalis (Hendel) is an economically devastating pest of fruit crops across the globe with stringent quarantine restrictions to limit its further spread. The current management programs increasingly depend on male annihilation but trapping female flies is equally important to reduce fruit damage. Considering the importance of kairomones in courtship and oviposition site selection behavior of B. dorsalis, the aim of this work was to isolate and identify potential cues from the volatiles of arils of jackfruit, Artocarpus heterophyllus. Using olfactometer assays and gas-chromatography linked to electroantennographic detection, attraction of both female and male B. dorsalis to specific jackfruit volatiles was demonstrated. Ethyl 3-methylbutanoate, ethyl hexanoate, pentyl butanote, 2-methylbutyl 3-methylbutanoate, 2-methylpropyl hexanoate, (Z)-3-hexenyl 3-methylbutanoate and dodecanal were found to attract female B. dorsalis specifically. Butyl acetate, 2 phenylethanol and pentyl 3-methylbutanoate elicited attraction in male B. dorsalis only. Synthetic blends of these compounds were found to attract female and male B. dorsalis in laboratory as well as field conditions. Using specific cues common to each set, a blend of methyl 3-methylbutanoate, butyl acetate, 3-methylbutyl acetate and hexyl acetate attracted both sexes of B dorsalis. This study demonstrates the use of kairomone-based lures for sex-specific as well as bisexual attraction for the first time.

Exploring the Transient Microbe Population on Citrus Butterfly Wings.

Microbes carve out dwelling niches in unusual environments. Insects, in general, have been hosts to microbes in different ways. Some insects incorporate microbes as endosymbionts that help with metabolic functions, while some vector pathogenic microbes that cause serious plant and animal diseases, including humans. Microbes isolated from insect sources have been beneficial and a huge information repository. The fascinating and evolutionarily successful insect community has survived mass extinctions as a result of their unique biological traits. Wings have been one of the most important factors contributing to the evolutionary success of insects. In the current study, wings of Papilio polytes, a citrus butterfly, were investigated for the presence of ecologically significant microbes within hours of eclosing under aseptic conditions. Scanning electron microscopy (SEM) revealed the presence of bacteria dwelling in crevices created by a specific arrangement of scales on the butterfly wing. A total of 38 bacterial isolates were obtained from the patched wings of the citrus butterfly, and Bacillus spp. were predominant among them. We probed the occurrence of these microbes to assess their significance to the insect. Many of the isolates displayed antibacterial, antifungal, and biosurfactant properties. Interestingly, one of the isolates displayed entomopathogenic potential toward the notorious agricultural pest mealybug. All the wing isolates were seen to cluster together consistently in a phylogenetic analysis, except for one isolate of Bacillus zhangzhouensis (Papilio polytes isolate [Pp] no. 28), suggesting they are distinct strains. IMPORTANCE This is a first study reporting the presence of culturable microbes on an unusual ecological niche such as butterfly wings. Our findings also establish that microbes inhabit these niches before the butterfly has contact with the environment. The findings in this report have opened up a new area of research which will not only help understand the microbiome of insect wings but might prove beneficial in other specialized studies.