BEHAVIOR Stridulation by Jadera haematoloma (Hemiptera: Rhopalidae): Production Mechanism and Associated Behaviors 1 2,3 1 2 ARIEL F. ZYCH, R. W. MANKIN, JAMES F. GILLOOLY, AND EVERETT FOREMAN Ann. Entomol. Soc. Am. 105(1): 118Ð127 (2012); DOI: http://dx.doi.org/10.1603/AN11048 ABSTRACT The Hemiptera displays a notable diversity of vibratory communication signals across its various families. Here we describe the substrate and airborne vibrations (sounds), the mechanism of production, and associated behaviors of Jadera haematoloma Herrich-Schaeffer, a member of the family Rhopalidae. Adult males and females both produce short, stereotyped sound bursts by anteriorÐ posterior movement of abdominal tergites I and II against a stridulitrum located on the ventral surface of the metathoracic wing. Sound bursts are produced by a single adult male or female when physically touched by another adult, and are strongly associated with being crawled on by the approaching individual, but are not produced in response to contact with other arthropods or when pinched with forceps. The propensity to produce sounds when crawled upon decreases during the mating season. These sound bursts by J. haematoloma likely are communication signals. Rhopalidae has been signiÞcantly absent from the vibratory communication literature until now. Although the sounds are produced using a mechanism common to vibratory communication systems in closely related Het- eropteran Hemiptera, the sounds in these other species function primarily in courtship or in motherÐ daughter interactions, which suggests that the functions of stridulation and the behavioral contexts have diversiÞed in the Heteroptera. KEY WORDS insect communication, mating, stridulation, Heteroptera Acoustic and vibratory communication is incredibly Rhopalidae (Hemiptera: Heteroptera), Jadera haema- diverse and has arisen multiple times during the evo- toloma Herrich-Schaefer, and describe for the Þrst lution of Hemiptera. The evidence in support of mul- time the mechanism and behavior associated with tiple evolutionary origins of vibratory communication vibrations in this family. in this group is quite extensive because of the char- Jadera haematoloma is an abundant rhopalid acteristic morphology of diverse vibration-producing throughout the continental United States that has structures in several families (Ashlock and Lattin 1963, been well-studied as an example of rapid evolution Schaefer 1980, Schaefer and Pupedis 1981, Polhemus associated with host plant shift (Carroll and Boyd 1994, Tishechkin 2006). Hemiptera occupy a wide 1992). Jadera sp. play a role in reducing the seed array of niches and communicate in many different productivity of a species of Sapindaceae (Koelreuteria ecological and behavioral arenas (Cocroft and Rodri- elegans Laxmann) classiÞed as a Class II Invasive by guez 2005). Comparisons of the structures used for the Florida Exotic Pest Plant Council (Carroll et al. vibratory communication among distantly related 2003, FLEPPC 2009). Rhopalids also are pests in coun- Hemipteran taxa may improve understanding of the tries where Sapindales such as Lychee and Longan are behavioral and ecological pressures that drive acoustic cultivated (Waite and Hwang 2002). convergence or diversiÞcation in insects. However, The opportunity to investigate rhopalid-produced elaborating Hemiptera as a clade for studying acoustic vibrations came from a chance discovery that groups evolution requires a good record of the diversity of of J. haematoloma placed into a bucket for transfer signals and signal-producing structures, a record that from a Þeld site to a laboratory produced audible is still incomplete. Here we investigate the vibrations sounds. A search of the literature revealed no infor- produced by a well-studied member of the family mation about sound production by this species, and only minimal information about substrate or airborne The use of trade, Þrm, or corporation names in this publication does communication in Rhopalidae. In spite of their eco- not constitute an ofÞcial endorsement or approval by the United logical and economic importance, a single recording of States Department of Agriculture, Agricultural Research Service of any product or service to the exclusion of others that may be suitable. a male Arhyssus hyoscyami L. is the only documenta- The USDA is an equal opportunity provider and employer. tion of sounds by species in this group (formerly Cori- 1 Department of Biology, University of Florida, Gainesville, FL zus hyoscyami L., Gogala 1990). Consequently, a study 32611-8525. was initiated to: 1) record and analyze the sounds in 2 USDAÐARS Center for Medical, Agricultural, and Veterinary En- tomology, Gainesville, FL 32608. a behavioral context, 2) describe the mechanism of 3 Corresponding author, e-mail: [email protected]. sound production, and 3) explore whether sounds January 2012 ZYCH ET AL.: VIBRATORY COMMUNICATION IN J. haematoloma 119 produced may be used for communication among aggregations by using a bag net beaten against members of the same species or as aposematic threats branches containing seasonal aggregations (Zych to potential predators. 2010). IdentiÞcation was veriÞed with the help of The body parts used by other closely-related members of the Florida State Collection of Arthropods Hemiptera to produce vibrations provide clues to the in Gainesville, FL (Slater and Baranowski 1978, Schuh mechanism that may be used by J. haematoloma. Rho- and Slater 1995). Groups of up to 100 adults and palidae lies within the infra-order Pentatomomorpha, nymphs were housed in 2-liter plastic buckets with a diverse group that includes Lygaeidae, Pentatomi- screen lids and given fresh host leaves and water from dae, Coreidae and other families with species known soaked wicks. Host seeds were omitted from enclo- to communicate through vibrations (Henry 1997). In sures to accurately reßect seed availability in the Þeld the Pentatomomorpha, a tergal plate formed by the at the time of collection (no intact seeds were present fusion of abdominal tergites I and II commonly is at the collection site). The buckets were held in a associated with vibratory communication that may be growth chamber maintained at 26ЊC with a photope- used in Rhopalidae (reviewed by Virant-Doberlet and riod of 14:10 (L:D) h to simulate summer temperature Cˇ okl 2004, Gogala 2006). Two mechanisms of the ter- and photoperiod. Individuals were housed for up to 2 gal plate have been proposed as the vibrational mech- wk before being returned to the Þeld and replaced by anism. The Þrst is as a plectrum used in conjunction new Þeld collections. Acoustic vibratory, and video with a wing stridulitrum (Leston et al. 1954, Ashlock recordings of groups of individuals were conducted at and Lattin 1963, Schuh and Slater 1995). The second 26ЊC and 60% RH in a vibration-shielded anechoic is as a “tymbal”; a bi-stable plate that pops in and out chamber (Mankin et al. 1996) at the Center for of two stable conÞgurations, similar to that used by Medical, Agricultural, and Veterinary Entomology, cicadas and planthoppers (Gogala et al. 1974, Gogala Gainesville, FL. 2006). The tymbal mechanism was Þrst hypothesized Sound Recording and Analysis. To fully character- for Cydnidae, where Gogala 2006 and colleagues ize the vibrations produced by J. haematoloma, it was (showed that wax application between tergites I and important to record and describe both substrate and II silenced low-frequency signals. Subsequent repli- airborne (acoustic) vibrations, as well as identify vari- cations of this technique have turned up conßicting ation among individuals. To capture both acoustic and results [Lawson and Chu 1971, Numata et al. 1989]). vibratory recordings, nine tests were conducted with Other vibrations in Pentatomomorpha have been at- 10Ð12 individuals placed in a cylindrical cage (6 cm tributed to a tymbal mechanism without direct obser- diameter by 10 cm height) made of 1-mm metal screen vation or manipulation of the tergum (Schaefer 1980, mesh for 30 min. An accelerometer (Bru¨el and Kjaer Virant-Doberlet and Cˇ okl 2004). Using J. haema- [B&K], Naerum Denmark) for recording substrate- toloma, it is possible to address not only the persis- borne vibrations (Wenninger et al. 2009) was clipped to tence of tergal plate involvement in sound production the top edge of the screen lid. These accelerometer in Pentatomomorpha, but also determine whether it recordings were coupled with acoustic recordings by functions as a tymbal or a plectrum. using a B&K microphone (Mankin et al. 2000) horizon- Before the sounds and sound-associated morphol- tally positioned atop a foam block 1 cm from the cage. ogy described in this report could be contributed to Both acoustic and substrate-borne vibrations were re- the body of literature on the diversity of insect signals, corded at the same time to determine whether they were it was important to distinguish between random or produced synchronously and to determine how each incidental sounds and those that may serve a role in differed from the other. All recordings were digitized communication. To disprove that sounds are pro- and saved on a computer using a commercially available duced randomly, we Þlmed interactions and then speech analysis system (Wenninger et al. 2009). asked whether sounds were associated with speciÞc To determine whether sex or body length inßu- behaviors and participants. We then identiÞed intra- enced variation in the sounds produced, a separate set and inter-speciÞc interactions that may play a role in of recordings were made of adults of known sex and communication, such as a defensive response to pred- body length. Body length was measured as the tip of ator threats (Masters 1979) or as an attractive signal to the clypeus to the posterior edge of the last abdominal conspeciÞcs (Wenninger et al. 2009). This behavioral segment. Nineteen adults whose sex and body length context will play an important role in our future un- were determined (Carroll and Loye 1987) were indi- derstanding of how vibrations are used for communi- vidually placed in the anechoic chamber setup with an cation in the Rhopalidae and other related families.