Waveform Library for Chinch Bugs (Hemiptera: Heteroptera: Blissidae): Characterization of Electrical Penetration Graph Waveforms at Multiple Input Impedances

Authors

Elaine A. Backus, USDA-ARSFollow
Murugesan Rangasamy, University of Florida
Mitchell Stamm, University of Nebraska-LincolnFollow
Heather J. McAuslane, University of FloridaFollow
Ron Cherry, University of FloridaFollow

Document Type

Article

Date of this Version

7-2013

Citation

Annals of the Entomological Society of America 106:4 (July 2013), pp. 524-539.

doi: 10.1603/AN13-15

Comments

U.S. Government Work

Abstract

Electrical penetration graph (EPG) monitoring has been used extensively to elucidate mechanisms of resistance in plants to insect herbivores with piercing-sucking mouthparts. Characterization of waveforms produced by insects during stylet probing is essential to the application of this technology. In the studies described herein, a four-channel Backus and Bennett AC-DC monitor was used to characterize EPG waveforms produced by adults of two economically important chinch bug species: southern chinch bug, Blissus insularis Barber, feeding on St. Augustinegrass, and western chinch bug, Blissus occiduus Barber, feeding on buffalograss. This is only the third time a heteropterans species has been recorded by using EPG; it is also the first recording of adult heteropterans, and the first of Blissidae. Probing of chinch bugs was recorded with either AC or DC applied voltage, no applied voltage, or voltage switched between AC and DC mid-recording, at input impedances ranging from 10⁶ to 10¹⁰Ω, plus 10¹³ Ω, to develop a waveform library. Waveforms exhibited by western and southern chinch bugs were similar, and both showed long periods of putative pathway and ingestion phases (typical of salivary sheath feeders) interspersed with shorter phases, termed transitional J wave and interruption. The J wave is suspected to be an X wave, that is, in EPG parlance, a stereotypical transition waveform that marks contact with a preferred ingestion tissue. The flexibility of using multiple input impedances with the AC-DC monitor was valuable for determining the electrical origin (resistance vs. electromotive force components) of the chinch bug waveforms. It was concluded that an input impedance of 10⁷Ω, with either DC or AC applied voltage, is optimal to detect all resistance- and electromotive force–component waveforms produced during chinch bug probing. Knowledge of electrical origins suggested hypothesized biological meanings of the waveforms, before time-intensive future correlation experiments by using histology, microscopy, and other techniques.