Schematic representation of the response of flies with different rearing histories towards γ-octalactone. <i>B. dorsalis</i> was reared on 3 different hosts.

<p>The final (third) generation gravid females were used in oviposition bioassays. A one-tailed <i>t</i> test revealed a significant difference (<i>P</i><0.0001) between Test (OL, γ-octalactone present) and Control (No OL, γ-octalactone not present). One-way ANOVA between the tests of group 1 (mango), 2 (banana) and 3 (guava) showed no significant difference in the mean no. of eggs laid.</p

γ-Octalactone is an oviposition stimulant and an oviposition site recognition cue.

<p>(a) The clear discrimination of the untreated (No OL, γ-octalactone not present) half (A) and γ-octalactone treated (OL, γ-octalactone present) half (B) by <i>B. dorsalis</i> in a single plate two-choice assay. (b) Number of eggs laid into treated and untreated pulp (one-tailed paired <i>t</i> test, <i>n</i> = 30, <i>t = </i>11.27, <i>df</i> = 19, <i>P</i><0.0001). Error bars = standard error of mean.</p

Behavior and egg-laying response of <i>B. dorsalis</i>.

<p>(a) Behaviour assay where <i>B. dorsalis</i> were presented with a filter paper disc containing γ-octalactone. Arrows show the hallmark oviposition behavior of extending the ovipositor and probing action (for better view watch <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0085764#pone.0085764.s003" target="_blank">video S1</a>). (b & c) Egg-laying response of <i>B. dorsalis</i> to a pulp disc with γ-octalactone (Test) or without (Control) in a 24-h oviposition bioassay. More eggs were laid on the test disc (<i>P</i><0.0001, one-tailed paired <i>t</i> test of non-transformed data). Error bars = Standard error of mean.</p

γ-Octalactone is a crucial cue that elicits oviposition in <i>B. dorsalis</i>.

<p>(a) Flies were allowed to oviposit into an empty agar disc. Area A contained all EAD active mango cues (cv. Alphonso) at natural ratios except γ-octalactone; Area B contained γ-octalactone alone. Flies could clearly distinguish between the untreated area (A) and the γ-octalactone treated area (B) (One-tailed <i>t</i> test, <i>t</i> = 6.610, <i>df</i> = 8, <i>P</i><0.0001). (b) The mean number of eggs laid into A or B. Oviposition in <i>B. dorsalis</i> was mediated by γ-octalactone. Error bars = Standard error of mean.</p

EAG and ovipositional response of <i>Bactrocera dorsalis</i> to varying concentrations of γ-octalactone.

<p>Control = Hexane; SEM: Standard error of mean; Means within a column followed by the same letters ^a or ^b are not significantly different at <i>P</i><0.001 (ANOVA); ppm: parts per million.</p