RECREATINGDEATH'S ACRE IN THE SCHOOLYARD: Using Pig Carcassesas Model Corpses z ToTeach Concepts of ForensicEntomology & EcologicalSuccession 0-

KENNETHG. SCHOENLY NEALH. HASKELL DAVIDK. MILLS CARINEBIEME-NDI KRISTIELARSEN YER LEE i-9

V) Downloaded from http://online.ucpress.edu/abt/article-pdf/68/7/402/53800/4452028.pdf by guest on 28 September 2021 t the "BodyFarm," nature takes its course, In homicides and other cases, time-since-death )-q with corpsesburied in shallowgraves, submerged in (called the interval or PMI) has special water,concealed beneath slabs of concrete,locked in relevance to crime scene investigators because such trunksof cars.As stand-insfor murdervictims, they knowledge narrows the field of possible suspects or the 0- servethe needsof science- and the causeof justice. passage of other events. Typically,the coroner or medical from W. Bass and J. Jefferson (2003) examiner takes legal chargeof a dead body and relies on the forensic z Death's Acre: Inside the Legendary pathologist to estimate the PMI. However, pathology-basedPMI indicators (e.g., body temperature, Forensic Lab-The -Where rigor mortis, livor mortis) appear early, usually within the Dead Do TellTales the first 72 hours (Henssge et al., 2002). On the other Each year hundreds of human bodies and skeletal hand, insect indicators interpreted by a forensic ento- remains are uncovered as the result of accidental discov- mologist have lengthier and more staggered timetables S, ery, archeological excavation, and reports of foul play. that can persist for weeks, months, or even years on The position and location of human remains in rela- a human body before discovery. When dating human tion to other artifacts;the degree and nature of insect remains, forensic entomologists primarily use thermal involvement; and the state of decomposition, preserva- development to backtrackegg laying of adult flies (called tion, and medical condition all provide important clues development-based PMI estimation) and, secondarily, about the cause, manner, and time of death that the arthropod replacement patterns of adults and larvae law requires to be ascertained. Application of scien- (called succession-based PMI estimation). Beyond PMI tific principles and methods from the fields of forensic estimation, forensic entomologists have been consulted pathology, anthropology, and entomology can yield on criminalcases involving child abuse, hospital neglect, significant clues from these scenes. Nowhere have such contrabandtrafficking, and wildlife poaching. clues been more forthcoming than at the 's Anthropology Research Facility or "Body Forensic entomology, now at least 150 years old, Farm,"where, in 1981, Dr. William Bass founded the has been accepted as scientific testimony in court- world's first outdoor laboratory devoted exclusively to rooms in at least 30 U.S. states and in many countries the scientific study of postmortem human decay (Bass around the world. Recent publications on the subject & Jefferson, 2003). include three textbooks (Smith, 1986; Byrd & Castner, 2001; Greenberg & Kunich, 2002), a handbook for law enforcement and crime scene investigators (Catts KENNETHG. SCHOENLY,Ph.D., is Associate Professor of & Haskell, 1990), three autobiographies by some of Biological Sciences at California State University,Stanislaus, its most noted practitioners (Erzinclioglu, 2000; Goff, Turlock,CA 95382; e-mail: [email protected]. 2000; Benecke, 2005), and four books for the lay public NEALH. HASKELL,Ph.D., is Associate Professorof Forensic on forensic science with chapters devoted to forensic Science and Biology at SaintJoseph's College, Rensselaer,IN entomology (Sachs, 2001; Bass &Jefferson,2003; Roach, 47978; e-mail: [email protected] K. MILLS, 2003; Innes, 2005). The National Institute of Justice Ph.D., is Associate Professor of Biological Sciences at the whose mission is to fund new technologies and training Institute for Micromanufacturing at Louisiana Technical programs in forensic science has, since 1994, funded University, Ruston, LA 71272; e-mail: [email protected]. forensic entomology research proposals. Case studies CARINEBIEME-NDI (e-mail: [email protected]), KRISTIE and researchresults in forensic entomology continue to LARSEN(e-mail: [email protected]), and YERLEE (e- draw national and international attention on network mail: [email protected])areformer undergraduatestudents and cable television programs,radio documentaries,and in the Department of Biological Sciences at California State national news magazines. University,Stanislaus, Turlock,CA 95382.

402 THEAMERICAN BIOLOGY TEACHER, VOLUME 68,NO. 7, SEPTEMBER2006 e1.Environmental andbiological variables that are known to influencecarcass decay rates, successional processes, and/or arthropod species composition.

VARIABLE(S) [ COMPARISON SUGGESTEDREFERENCE Sunlightand Heat Sun-Exposedvs.Shaded Carcasses Shean,B.S.et al. 1993.J. Forensic Sciences 38:938-949. Season Springvs. Summer Tabor,K.L. et al.2004.J. Medical Entomology 41:785-795 Dwellingsand Shade Indoorsvs. Outdoors Goff,M.L. 1991.J. Forensic Sciences 36:748-753. DielActivity Diurnalvs. Nocturnal Schoenly,K.G. 1983.J. N. Y Entomological Soc.91: 342-347. Concealmentand Burial Surface-Exposedvs.Buried Carcasses VanLaerhoven,S.L.and G.S. Anderson. 1999.1. Forensk Sciences 44:31-41. Clothingand Vertebrate Clothed/Scavengedvs.Clothed/ Komar,D.and 0. Beattie.1998.J. Forensk Siences 43: 792-796. Scavenging UnscavengedCarcasses Fire Burntvs. Unburnt Carcasses Avila,F.W. and M.L. Goff. 1998.J. Forensic Sciences 43: 581 -586. Water Submersedvs.Unsubmersed Carcasses Payne,J.A. and E.W. King.1972.J. Georgia Entomological Society 73:153-162. InsectAccessibility Insect-OpenCages vs. Insect-Proof Cages Payne,J.A. 1965. Ecology 46:592-602.

InsectPredators Fire-AntPresence vs. Fire-Ant Absence Wells,J.D.andB.Greenberg. 1994.1. Medical Entomology 31:171-174. Downloaded from http://online.ucpress.edu/abt/article-pdf/68/7/402/53800/4452028.pdf by guest on 28 September 2021

In this article, we describe how to construct a mock beetles (Scarabaeidae), clothes moths (Tineidae), crime scene, acquire a pig carcass, sample its arthropod and perhaps several others. fauna, integrate photographic, climatic and arthropod suc- * In unembalmed carcasses lying on the ground, the cessional data, and estimate the PMI from insect succes- carrion-arthropodcommunity proceeds as a con- sional timetables. (For a complementary classroom activity tinuum of gradual changes, not as a series of neatly on development-basedPMI estimation, see Carloye,2003.) defined decay stages with distinct arthropod faunas The experimental layout we describe below represents in each. the untreated control or background condition (i.e., sur- * characterizephysical face-exposed, unclothed, and unscavenged by vertebrates) Decay stages are often used to in a carcass, however, they against which other treatmentscan be compared (e.g., bur- and chemical changes or disappearanceof ied, burned, submerged, clothed, or vertebratescavenged; rarely delineate the appearance in successional process. see Table 1 for other examples). Exposing pairs of carcasses entire arthropodgroups the to contrasting environmental and biological conditions * Carcass decay rates and carrion-arthropodsucces- invites students to explore factors that affect carcass decay sion are affected by season, temperature,exposure rates, order and timing of arthropod succession, and spe- mode, accessibility to insect and vertebratescaven- cies composition. This activity can be incorporated into a gers, degree of concealment, and countless other high school or college-levelforensic science, entomology, or factors. ecology course to illustrate working principles of forensic * Succession aboveground continues with succession entomology or ecological succession or both. Outputs of belowground as the products of carcass decay this activitycan be stored in electronic (Excel) spreadsheets alter the underlying soil structure and biota while (or tabulated on graph paper) and/or digitized images and introducing nutrients for subsequent and enhanced then discussed in relation to actual cases published in the plant growth. forensic science literature.Some of the outcomes students are likely to experience (i.e., see, smell, touch, and even Carcass Acquisition & Handling hear) are listed here and below: Forensicentomologists view the 50-lb domestic pig (Sus * Blow Ries (Family Calliphoridae),typically the most scrofaLinnaeus) as the most promising "model corpse" for reliableand most abundant PMIindicators for devel- both teaching and research due to its similarityto humans opment-based estimation, can lay up to 300 eggs in internal anatomy, fat distribution, size of chest cavity, at a time, typically 3 times in their lifetime, and are and lack of heavy fur (Catts, 1992; Byrd & Castner,2001). generally(with ants) the first insects to discover and Pigs also share with humans an omnivorous diet, indicat- colonize a human body. ing that they may have a similar gut fauna (Anderson & * The insects that hold promise as succession-based VanLaerhoven,1996). Beforeplanning this activity,contact PMI indicators, whose abundances vary sever- your superintendent or supervisor to determine what regu- al thousand-fold on a carcass, are the blow flies lations exist for registering,obtaining and using vertebrate (Calliphoridae),flesh flies(Sarcophagidae), house and animals (living or dead) for teaching. At the college level, latrine flies (Muscidae), skipper flies (Piophilidae), animal welfare committees must approve all teaching and soldier flies (Stratiomyidae),coffin flies (Phoridae), research projects that involve vertebrate animals; at the small dung flies (Sphaeroceridae), hide beetles middle and senior high levels, similarapprovals may involve (Dermestidae), rove beetles (Staphylinidae), clown both administrator and parent groups. When contacting beetles (Histeridae), ham beetles (Cleridae), dung potential sources (e.g., pig farms, slaughterhouses,livestock

PIGCARCASSES ASMODEL CORPSES 403 dealers, agriculturaluniversities) explain the nature of your day, each jar is filled 3-cm deep with alcohol, placed into the inquiry and ask about cost and pickup arrangements.Pigs PVCpipe, then covered with the funnel. A day markerwith free of disease that have died of accidentalor naturalcauses changeable 38-mm high, reflectivemetal digits, constructed are preferableto those that requireeuthanasia because they from plastic wood and a mailbox address frame (Figure may be obtained at no cost. In cases when euthanasia is 1, Table 2), is attached to a stake and hammered into the unavoidable, enlist the help of a USDA-licensedlivestock groundjust left of the carcass.A weather station, in the form dealer.During transport,carcasses should be handled using of a "4 by 4" by 2-m long verticalpost, is installed 1 m from heavy leather, latex, or polyethylene gloves and double bagged or covered in other ways to prevent prematureinsect colonization.Acquiring and laying Tabe 2. Materialslist and vendor sources for constructing the mock crime scene and out carcassesafter sunset also minimizes premature forsampling and processing carcass-frequenting arthropods. colonization because blow flies rarelyfly at night. ITEM,QUANTITY, SIZE AND CATALOGUE NUMBER VENDOR Constructing the Mock Crime A.Mock Crime Scene (about $250) Scene * 1"xl" meshwelded wire (3' highx 30' long) Localhardware stores To reduce construction costs, instructors * hogrings(#H1),ringerpliers(#RR-HM) | SeymourManufacturing should solicit donations from local hardwarestores * 4 rubbertie downs(79 cm long), 8 S-hooks OzarkTrail Downloaded from http://online.ucpress.edu/abt/article-pdf/68/7/402/53800/4452028.pdf by guest on 28 September 2021 and ask for assistance from parent and student * 4 sections(152 cm long) of 13mm diam. I volunteers. The best possible sites for this project reinforcementbaror"rebar" | Localhardware stores are those on level ground with good drainageaway from buildings and normal foot traffic.To reduce * 4 plastictent stakes Localhardware stores the effects of two- and four-leggedscavengers, the * 4 sectionsof PVCpipe (10 cm diam. x 20cm long) | Localhardware stores carcass is placed inside two welded-wirecages of a * 4 canningjars and metal lids (1 pintsize) Localsupermarkets double-nested design (both with 1 in x 1 in mesh), * 4 plasticfunnels (10cm max. diam.) Localsupermarkets such that the smaller cage (60 x 60 x 90 cm) fits * mailboxaddress frame cm 2 setsof inside the larger (90 x 90 x 120 cm) (Figure 1, (17 long), ColeConsumer Products Table 2). Cages are held together using hog rings metaldigits, letters 'd-a-y'(see Figure 1) and ringer pliers. The outer cage slides up and * Raingauge (#88991), maximum/minimum I down on four reinforcementbars or "rebar"ham- thermometer(#89024) | ForestrySuppliers mered into the ground at each corner at a depth * 4" x 4" verticalpost (2 m long),signboards, of 30 cm. Rubbertie downs and S-hooks, with one plasticwood for day marker (see Figure 1) Localhardware stores end looped around each rebarand the other end to a tent stake, secure the outer cage to the ground at B.Field Sampling (about $75) each corner.Inside the "alley"between the two cages * knapsack,workman's gloves Askstudents to bring are four pitfall traps that are buried along the four * 4 canningjars and metal lids (1 pintsize) Localsupermarkets cardinal directions (N, S, E, W) to collect surface- * 70%ethanol* BioquipProducts active arthropods.Each pitfall trap was constructed from a 20-cm section of 10-cm diameter PVC pipe, * aerialsweep net (#7112NA) | BioquipProducts a 1-pint wide-mouth canning jar, and a 10-cm * penetration(=turkey) thermometer Localsupermarkets maximum diameter plastic funnel with its stem * miscellaneous(forceps, magnifying lens, removed.Each PVCpipe is buried verticallywith its disposablegloves, self-sealing bags, clipboard, top edge just below ground level. On each sampling pencils,permanent markers, camera) Askstudents to bring C.Specimen Processing (about $150) Figure 1. ofthe mock crime scene. Experimentallayout * 70%ethanol* BioquipProducts Drawingby Tosti. Margaret * rustproofinsect pins (#1202B), insect exam- 4"x 4" inationstage (#6185), insect pinning block (#1144), vertical insectstorage drawer kit (#lOIOB or 1012B) BioquipProducts rebar(4) weldedwire post ? cages(2) sign dissectingmicroscope School boards(2) * smallkitchen strainer Localsupermarket ? cafeteriatrays (for sorting out daily catch) School rubbertie rain thrmomete gae * onegraduated cylinder (100 ml) School * LaserJetprinter, card stock (specimen labels pitfalltraps madein 4-pt fonts) Askstudents to make * miscellaneous(pencils, permanent markers, E Sthooks'8) babyfood jars with leakproof lids) Askstudents to bring day photographic marker station tentstakes (4) g* 6.66 go, 6666.6 * 6. 6 *6*.6 M

404 THEAMERICAN BIOLOGY TEACHER, VOLUME 68, NO.7, SEPTEMBER2006 the cages and secures a rain taxonomic keys and study gauge and max/min ther- Table3. Generalchecklist of fieldprocedures for gathering entomologi- specimens from different mometer (Figure 1, Table cal,climatic, and photographic data in the model corpse study. arthropod families they are 2). Signboards on the post likely to encounter.Another identify the project's direc- 1. Inthe lab, fill each of the four pint jars 3-cm deep with alcohol. useful taxonomic refer- tor, purpose, significance, 2. Puton leather gloves and work in pairs to removeand set aside cages. ence is the ForensicInsect and contact information. A Cards(Castner 3. Removejars from the pitfalls and seal with lids. Replace old jars with Identification tripod and weighing balance & Byrd, 1995), which fea- newjars containing fresh alcohol; re-position funnels over the jars. to record daily weight loss ture color photographs and of the carcass is planned 4. Tocollect flying insects, apply the net back and forth over the body with life-history descriptions of in future versions of this a rotationof the net opening 1800 for each of five successive passes. 50 forensically important activity (for a description of Alternatively,holding the tail of the net above the insects while swat- insect species. Before trav- the method and different tingdownward isalso effective. eling to the site, a checklist weight loss measures, see 5. Transfercollected arthropods from the net bag into one or more coded outlining the data gather- Shahid et al., 2003). jarscontaining alcohol. Allow insects to resettleon remains before tak- ing procedures (Table 3) is inga secondnet sample. discussed with the whole Procedures class followed by assign- 6. Checkthe nine body orifices (i.e., eyes, nostrils, mouth, ears, anus, uro-

ment of specific tasks Downloaded from http://online.ucpress.edu/abt/article-pdf/68/7/402/53800/4452028.pdf by guest on 28 September 2021 Before starting this genitalopening) for sites of egglaying by colonizing adult flies. If one (e.g., photographer, speci- activity, alert campus secu- ormore maggot masses are present, collect several hundred and record men collector[s], weather rity and administrators theirinternal (center) and edge temperatures using the penetration in writing of the project's recorder) to selected stu- (turkey)thermometer, and compare with ambient air temperatures dents (Figure 2). Except starting date. In the class- recordedfrom the max/min thermometer. room, students are briefed for pitfall traps-which are 7. Inspectand collect handfuls of soilaround remains for post-feeding lar- on design features of the impracticalto use at actual mock crime scene and are vae,pupae, and other soil invertebrates. Place any collected specimens death scenes-this checklist reminded of the humane ina codedvial. follows the steps forensic procedures they must fol- 8. Liftup remains for any additional insects that may not have been entomologists urge crime low when sampling from trappedby either pitfall traps or sweep nets. Possible taxa include sil- scene investigators use the pig. After reviewing phid(carrion) beetles, trogid (skin) beetles, scarab (dung) beetles, and when collecting insect evi- the background informa- otherarthropods that may tunnel under or use the remains for shelter dence before body removal tion and cited references, ormating. (Byrd & Castner,2001). the instructor starts by ask- 9. Recordmaximum and minimum temperatures and report any precipi- During the sampling ing his/her students which tationon data sheet. Reset the max/min thermometer and dump out phases of this activity, we environmental or biological anyaccumulated water from the rain gauge. have found that students variable(s) they wish to test. work well in groups of 10.Revise the day marker and photograph the remains making sure to For example, at Louisiana three to five; however, the Technical University where includethe day marker inthe camera's visual field (lower left corner). entire class is tested on all two of the authors co-devel- Photographany unusual events (e.g., animal tracks, predator-prey components of the project. oped a course in 1994 behavior,maggot masses, recently eclosed adults, etc.). Record the Typically,daily data gather- titled "Investigative Field numberof photographstaken on the data sheet. ing at a carcass requires Techniques in Forensic 11.Replace cages and re-secure tarp straps. only 15-20 minutes and Science," two pig carcasses can he reneated for neriods were placed on level ground of 30 days or more. After in contrastingenvironments (i.e., full Figure2. Studentsand instructor (in background) returning from the field, students sun vs. shade) to study the interac- collectingarthropod samples, weather data, and are instructed to double-label each tive effects of light, temperature,and photographs.Photo by Steve Wolf. collection Jar and complete the top humidity on carcass decay rates and two rows of a daily data sheet that arthropod succession. Similarly,the includes the following: date, time, senior author has taught "Medical maximum air temperature, mini- and VeterinaryEntomology" at CSU- mum air temperature,precipitation, Stanislaus using a 50-lb pig carcass photographs taken, and comments. during both the fall and spring Sorting, counting, and identifi- semesters permitting between-sea- cation of arthropodspecimens is the son comparisons of decay rates and most time consuming component of arthropodsuccession. Studies of car- this project; however, identification rnon-invertebratesuccession in the to the family level is often sufficient in aquatic environmentare reviewed for imparting the important foren- Merrittand Wallace (2001). sic, entomological, and ecological Before sampling begins, stu- concepts. In the days and weeks dents are acquaintedwith the use of to follow, student (and instructor)

PIGCARCASSES ASMODEL CORPSES 405 confidence builds as the same arthropod families appear and reappear in the samples. Formalized taxo- nomic keys for identifyingall ~00 -~~~ carrion-associatedarthropod families,including larvae,are II~~~~~~1 within reach of most school libraries and entomology r(N teaching labs (e.g., McAlpine, cn ~ ~ ~ ( 1981, 1987, 1989; Stehr, 1987, 1989; Greenberg & Kunich, 2002; Triplehorn& r E Johnson, 2005). In our spring 0) (~~~N 2004 study, processing time 0) slowed on Days 13-22 when 0- post-feedingmaggots migrat- -o r4~~( ed and filled pitfall jars. To (0 ~ ~ ~ r Downloaded from http://online.ucpress.edu/abt/article-pdf/68/7/402/53800/4452028.pdf by guest on 28 September 2021 improve counting efficiency, we used a 100 ml gradu- ated cylinder to volumetri- cally estimate daily maggot abundance. In later lectures, - 00 students were introduced to museum-quality methods of arthropod preservation, M- curation, and display. Extra credit went to those students LJn who properly pinned and = r labeled specimens belonging to underrepresentedfamilies r-L in the school's teaching col- lections. Laboratory tasks require that students handle preserved insects; conse- CL ) quently, common sense dic- tates that instructors require (0 students to wash their hands after each lab session. Successionalrecords can be reported on simple graph paper or as an electronic spreadsheet in Excel. In our 0) spring 2004 trial, 30 days of consecutivedaily sampling 0) yielded a data table in which r~~~40 cells of the table listed rela- tive counts of each family or order on each day (Table 4). While in Excel, taxa can o U ~~ ~ ~~~~~~~~~~~c be sorted (up or down) into .2 ~~~~~72o different feeding groups, as 0)4-' C) _ m - ~~~~)>- m 3.. W 6 - we have done in Table 4, -o L.o1-o ~ ~ ~ ~ C to separate the aboveground E 2;. . 4 - fauna (i.e., carrion feeders and their predators) from the belowground (i.e., soil) fauna. Within each feeding group, taxa can be sorted by order of appearance(i.e., ear-

406 THEAMERICAN BIOLOGY TEACHER, VOLUME 68, NO.7, SEPTEMBER2006 liest to latest), as we have also done rapid and dramatic changes in the in Table 4, to illustrate the succes- Figure3. DayO:The first (at arrow) physical and chemical makeup of the sional nature of the carrion-arthro- appearedon the carcass within 3 minutesafter carcass and in arthropod succession pod community (i.e., an orderlypro- placement.Photo by Kenneth Schoenly. were captured in the photographs gression of species additions and we took on the same spot each day. replacements).Food webs have also Some of these events are shown and accompaniedsuccessional timetables described in Figures 3-10. in carrionecology studies (e.g., Reed, 1958; Cornaby,1974). Estimating Time Becausethis projectrequires sev- of Death from eral weeks to complete, instructors Successional Data should take their class on frequent site visits and ask students to report Day-to-dayrecords of arthropod on their observations. As a home- counts, weather, and physicochemi- wxvorkassignment, ask students to cal changes in one or more carcasses think about sources of error in their constitute a "baseline study" for a sampling and observations.Variable particularregion, season, and set of catch efficiencyof differentinsect spe- ecological circumstances. In a death Downloaded from http://online.ucpress.edu/abt/article-pdf/68/7/402/53800/4452028.pdf by guest on 28 September 2021 Figure4. Day3: Greenish marbling onabdome investigation, insects sampled from cies in pitfall traps and sweep nets marksthe caused is one such example. Information putrefactionprocess byhemrolysis the human corpse are then matched exchange often stimulates additional ofblood vessels and the reaction ofhemoglobin and against those from the baseline questions and deeper understanding hydrogensulfidleiThe fauna present included blow carcass(es) whose successional time- of the underlyingscientific principles. flies,flesh flies, predatory rove beetles (staphylinids), tables are known. Some entomolo- PowerPointand poster presentations andants (formicids) (lable 3). Photo by Kenneth gists have also used species determi- are two effective methods we have Schoenly. nations frompreviously verified death used to improve both information cases to supplement and validate exchange and inquiry-based learn- their baseline records.Comparison of ing. These presentationsinclude the the baseline and corpse faunas yields same content and sections a refer- an upper and lower estimate of the eed journal paper would contain:an PMI, whose limits may converge on informativetitle, summary or abstract, the same day or may be several days descriptionof the problemand meth- long. Consequently,the ability of the ods used, salient results mixed with forensicentomologist to performsuc- graphs and photographs,and general cession-based estimates of the PMI conclusions. Students are graded on critically depends on the quality of clarity,written and oral delivery,sci- field data from baseline studies. entific accuracy,grammatical correct- To illustrate the PMI estimation ness and spelling, and creativity.A method, consider the hypothetical mock trialis anotherway to stimulate occurrence matrix shown in Table 5. student inquiry; this approach also Figure5. Day6: Carcass bloating has everted the In this example, there are 9 columns adds a healthydose of competitionas intestinaltract (at arrow), causing a feeding frenzy representingpostmortem Days 1-9 in the activty winds down (RichMerritt, byflies and beetles. Fluids emitted from the mouth the succession and thereare 8 baseline personalcommunication). andnose originated from the stomach and lungs. taxa, labeled A through H. Cells of Smallnumbers ofadult clown beetles (histerids) this matrixshow 1 for presence,and 0 Events in Carcass for absence. In this hypotheticalcase, werecollected. Maggot masses were discernible Decay & Arthropod representativesamples of the corpse aroundthe natural orifices (eyes, nose, mouth). Photo fauna are collected at the crime scene Succession byColleen Blackburn. and brought to the entomologist's Daily data gathering from a 50- laboratory.Upon analysis, the corpse lb pig carcassconducted over spring faunawas found to contain four mem- term 2004 on the CSUS campus bers of the baseline fauna:Taxa B, D, yielded a 30-day log of arthropod, G, and H (Note: All corpse taxa may photographic, and weather records. not be membersof the baseline fauna, Ground and aerial arthropods were and vice versa). The lower and upper collected every mid-morning (0900 limits for the PMI correspond to the - 1100 hrs) from 1 April to 30 April. first and last days, respectively,that Weather records (maximum and the four taxa are found together in minimum temperatures) revealed a the succession. In this example, the gradual warming trend interrupted lower and upper limits are Days 3 on 17 April by a light shower. The and 5, respectively(Table 5). TaxonH

PIGCARCASSES ASMODEL CORPSES 407 Figure 6. Day13: Large maggot masses have becomes the definitive taxon Figure9. Day25: Large numbers of newly for the lower limit because its begunto skeletonizethe head; their combined emergedadult flies (tenerals) perched on the cages arrivalcoincided with the Day wrigglingmotions emit a faintbut uniform rustling andthe nearby vegetation (at arrows) signaled their 3 lower limit and Taxon D sound.Partial collapse of the abdomen has released completionofone full generation on the carcass. becomes the definitive taxon trappedgas pockets that emit a fouland sicken- Breakupofthe skeleton (disarticulation) began with for the upper limit because ingsmell. At or near this period, the number of separationofthe lower jaw from the rest of the head. its last day in the succession arthropodfamilies reached peak richness. coincided with the Day 5 Photoby Photoby Colleen Blackburn. KennethSchoenly. upper limit. Discussion & Study Questions The public's fascination with forensic science is both a challenge and an opportu- nity for teachers. Although Downloaded from http://online.ucpress.edu/abt/article-pdf/68/7/402/53800/4452028.pdf by guest on 28 September 2021 entomology-based PMI esti- mation is one of the most powerfuland promisingtech- niques of modern forensic science, it is also one of the (Figure10. Day30:The dried remains resemble least understood (Greenberg Figure7. Day18: A light shower the day before parchmentand are riddled with insect emergence & Kunich,2002). One source hascaused a mass migration ofpostfeeding mag- holesas skeletal disarticulation continues. Photo by of confusion is why forensic gotsto overfill the pitfall trap at the endof entomologists require whole R_~~~~~~~V posterior KennethSchoenly. pig(see arrow). On this day, over 33,000 individual carcasses, rather than butch- insectswere collected inthe four pitfall traps. Photo ered meats, as model corps- byKenneth Schoenly. es. For this alternativeto be effective,it needs to simulate the whole animal but only if the underlying scientific principles are already well understood. When the prin- ciples themselves are being scrutinized and validated, as they still are in forensicento- mology, this alternativefalls short. Moreover,research has shown that butchered meats (e.g., drumsticks,fish filets, pork ribs) desiccate quickly,favor some blowflies over others, deny insect larvaenatural refuges to escape from predatorsand parasites(Smith, 1986), and lack the gastrointestinalapparatus that generates Figure8.Day 23:The carcass isnoticeably drier,no chemicalcues forattracting many necrophilous species. Exceptfor cases involv- maggotactivity was seen, and few flies were caught, ing dismembermentand scatteringof remains,butchered meats do not capture whileseveral dermestid larvae were collected under- the realistic elements investigators-in-trainingwill face when processing real crime scenes. Using whole carcassesinvites an endless numberand varietyof neaththe carcass. Photo by Colleen Blackburn. crime scenes inspired from actual cases in the primaryliterature (i.e., Journal of ForensicSciences, Forensic Sciences International, Journal o MedicalEntonmology, AnmericanJournal of ForensicMedicine and Pathology). An importantlesson in this activityis that death scenes are "specialhabi- tats"in the sense that human and other animal remains have shrinkingand uneven borderswhose close confinementpromotes a feedingand reproductive frenzyby colonizing invertebrates.Fresh carcassesfunction initiallyas empty islands thatrapidly concentrate regional biodiversity, attracting up to 150 inver- tebratefamilies (Payne & Crossley, 1966). When approached,many carrion- arthropodspecies fly off or slitheraway, becoming what forensicentomologists call "disappearingevidence" (Catts & Haskell, 1990). For teachers seeking inexpensive,replicable, and compactsystems for introducingbiodiversity con- cepts, carcassesare hard to beat.

408 THEAMERICAN BIOLOGY TEACHER, VOLUME 68, NO.7, SEPTEMBER2006 lesson reinforcedby this activity is that the Another Table5. Ahypothetical occurrence matrix for illustrating the method of carrion-arthropodcommunity proceeds primarilyas a con- succession-basedPMI estimation (1 = presence,O= absence). tinuum of gradualchanges, not as a series of neatly defined stages with distinct arthropodfaunas in each (Schoenly & CORPSEBASELINE POSTMORTEMINTERVAL (PMI) Reid, 1987; Greenberg,1991; Hall, 2001), as severalauthors, FAUNA FAUNA 1 2 3 4 5 6 7 8 9 past and present, have claimed or inferred. This point of controversyprovides an opportunityfor students to engage TaxonA 1 1 1 1 0 0 0 0 0 in moderateddebates about the practicaluses of decaystages TaxonB TaxonB 0 1 1 1 1 1 1 0 0 in death investigations(for examples, see Schoenly & Reid, TaxonC 0 1 1 1 1 1 0 0 0 1987). TaxonD TaxonD 1 1 1 1 1 0 0 0 0 Based on the data presented in Table 4 and the hypo- TaxonE 0 0 0 0 0 0 1 1 1 thetical death case described in Table 5, succession-based PMIestimation in an actual death investigationmight seem TaxonF 0 0 0 0 1 1 1 1 1 a straightforwardtask. However,PMI estimation can be ham- TaxonG TaxonG 1 1 1 1 1 1 1 1 0 pered by severalcomplications-besides those listed in Table TaxonH TaxonH 0 0 1 1 1 1 1 1 1 1 1 1-such as movement of the body, presence of poisons or narcoticsin body tissues, and unusual topographic,climatic, __. .'. EDiEhIIIE or other ecological circumstancesat the crime scene (Catts, Downloaded from http://online.ucpress.edu/abt/article-pdf/68/7/402/53800/4452028.pdf by guest on 28 September 2021 1992; Schoenly et al., 1992). We have also oversimplified the procedureforensic entomologists have devised for con- solving skills (Carloye,2003). In this field activity,students structingsuccessional timetablesfor PMIestimation. Because witness firsthand the interplayof arthropodsuccession and corpses often attract multiple members of the same insect carcass decomposition while learning the methods forensic family whose timetables are unlikely to overlap completely, entomologists use to estimate time of death in medicocrimi- entomologists must gather species-specificdata over several nal investigations. While instructors might find butchered seasons. These timetablesmay also include separaterows for meat less daunting than whole carcasses, the scientific and differentlife stages of the same forensically-importantspecies educational merits of using whole carcasses outweigh their (i.e., eggs, 1st instar larvae, 2nd instars, 3rd instars, pupae, added cost or inconvenience. For example, the rapid reduc- and adults). To add a level of complexity for an upper level tion of fluid and tissue losses from surface-exposed50-lb pig entomology class, teacherscould providestudents with taxo- carcassesduring summer-up to 40% of their startingweight nomic keys to the eggs, larvae,pupae, and adults of forensi- in 7 days (e.g., Shahid et al., 2003)-never ceases to amaze callyimportant fly and beetle species (Smith, 1986; Greenberg both students and instructors alike (M. L. Goff, personal & Kunich, 2002). A species list and timetable designed for communication). succession-basedPMI estimation, based on samples gathered from cat carcassesplaced at differentsites on Oahu, Hawaii, Acknowledgments is shown in appendices 1 and 2 of Schoenlyet al. (1992). The We thank Colleen Blackburnand Endre Szabo for their senior authorhas used this datasetto createhypothetical mur- field and lab assistance, MargaretTosti for drawing Figure der cases for take-homeexercises and test questions. 1, Dr. Steve Wolf for granting us permission to use Figure What can teachers do with the remains after the study 2, and to Vera Bryan and her 2004 MarysvilleHigh School is over?Several alternatives exist. When the bones have been biotechnology class for beta-testing this activity. We also picked clean, teacherscan "recycle"them by challengingstu- thank Eric Benbow,Vera Bryan, Rebecca O'Flaherty, Tommi dents to reassemblethe skeleton for a class projectin general Lou Carosella,M. L. Goff, David Hough, Rich Merritt,John zoology, comparativeanatomy, or mammalogy.Alternately, Wallaceand two anonymous reviewersfor their many useful retaining old sites while starting new ones allows students suggestions on an earlierdraft. to see how time and vertebratescavenging affect the order and scatter of the skeleton as a precursorto early fossil for- mation (called taphonomy; e.g., see Behrensmeyer& Hill, References 1980). Oldersites are also useful for teachingsurface recovery Anderson,G.S. & VanLaerhoven,S.L. (1996). Initialstudies on insect techniques used by forensic taphonomistsand archeologists successionon carrionin SouthwesternBritish Columbia. Journal ForensicSciences, 41, 617-625. (e.g., Haglund& Sorg, 2002). Weeks or months aftercarcass of Death'sAcre: Inside the Legendary removal, former sites will also continue to show evidence Bass, B. & Jefferson,J. (2003). ForensicLab - TheBody Farm - Wherethe Dead Do TellTales. New of altered soil structureand biota as well as enhanced plant York,NY: Putnam Press. growth and succession. Behrensmeyer,A.K. & Hill, A.P. (1980). Fossils in the Making: VertebrateTaphonomy and Paleoecology. Chicago, IL: University Conclusion of ChicagoPress. Benecke,M. (2005). Kriminalbiologie(Forensic Biology), 3rd Edition. Notwithstanding its importance to society and law BergischGladbach, Germany: Luebbe (in German). enforcement,forensic entomology holds a grisly fascination Byrd,J.H. & Castner,J.L. (2001). ForensicEntomology: The Utilityof to students, has all the elements of a good crime novel (Hall, Arthropodsin LegalInvestigations. Boca Raton,FL: CRC Press. 2001), and through simulated case studies and inquiry- Carloye,L. (2003). Of maggotsand murder:Forensic entomology in based approaches, can teach critical thinking and problem- the classroom.The American Biology Teacher, 65, 360-366.

PIGCARCASSES ASMODEL CORPSES 409 Castner,J.L.& Byrd,J.H. (1995). ForensicInsect Field IdentificationCards. Merritt, R. & Wallace, J.R. (2001). The role of aquatic insects in foren- ColoradoSprings, CO: Forensic Sciences Foundation. sic investigations. In J.H. Byrd & J.L. Castner (Editors), Forensic Catts,E.P. (1992). Problemsin estimatingthe postmorteminterval in Entomology:The Utility of Arthropodsin LegalInvestigations (pp. 177- death investigations. Journal of AgriculturalEntomology, 9, 245-255. 222). Boca Raton, FL: CRC Press. Catts, E.P. & Haskell, N.H. (1990). Entomologyand Death: A Procedural Payne, J.A. & Crossley, D. (1966). Animal species associated with pig Guide.E.P. Catts & N.H. Haskell(Editors). Clemson, SC: Forensic carrion. ORNL-TM1432. Oak Ridge, TN: Oak Ridge National EntomologyAssociates. Laboratory. Cornaby,B.W. (1974). Carrion reduction by animalsin contrastingtropi- Reed, H.B.Jr. (1958). A study of dog carcass communities in Tennessee, cal habitats.Biotropica, 6, 51-63. with special reference to the insects. AmericanMidland Naturalist, Erzinlioglu, Z. (2000). Maggots,Murder and Man. Colchester,UK: 59, 213-245. HarleyBooks. Roach, M. (2003). Stiff. The CuriousLives of Human Cadavers.New York, Goff, M.L. (2000). A Fly for the Prosecution:How Insect EvidenceHelps NY:W.W. Norton. SolveCrimes. Cambridge, MA: Harvard University Press. Sachs,J.S. (2001). Corpse:Nature, Forensics, and theStruggle to Pinpoint Greenberg,B. (1991). Flies as forensicindicators. Journal of Medical Timeof Death. Cambridge, MA:Perseus Publishing. Entomology,28, 565-577. Schoenly, K. & Reid, W. (1987). Dynamics of heterotrophic succession Greenberg, B. & Kunich, J.C. (2002). Entomologyand the Law: Flies as in carrion arthropod assemblages: Discrete series or a continuum ForensicIndicators. Cambridge, UK: Cambridge University Press. of change? Oecologia(Berlin), 73, 192-202. Haglund, W.D. & Sorg, M.H. (2002). Advancesin ForensicTaphonomy: Schoenly, K., Goff, M.L. & Early,M. (1992). A BASICalgorithm for calcu-

Method,Theory and ArchaeologicalPerspectives. Boca Raton, FL:CRC lating the postmortem interval from arthropod successional data. Downloaded from http://online.ucpress.edu/abt/article-pdf/68/7/402/53800/4452028.pdf by guest on 28 September 2021 Press. Journal of ForensicSciences, 37, 808-823. Hall,R.D. (2001). Introduction:Perceptions and statusof forensicento- Shahid, S.A.,Schoenly, K., Haskell, N.H., Hall, R.D. & Zhang, W. (2003). mology.In J.H. Byrd & J.L.Castner (Editors), Forensic Entomology: Carcass enrichment does not alter decay rates or arthropod com- The Utility of Arthropodsin Legal Investigations(pp. 1-15). Boca munity structure: A test of the arthropod saturation hypothesis at Raton,FL: CRC Press. the Anthropology Research Facilityin Knoxville, Tennessee.Journal Henssge, C., Knight, B, Krompecher,T., Burkhard,M. & Nokes, of MedicalEntomolog, 40, 559-569. L. (2002). The Estimation of the Time Since Death in the Early Smith, K.G.V.(1986). A Manual of ForensicEntomology. Ithaca: Cornell PostmortemPeriod, 2nd Edition. London, UK: Arnold. University Press. Innes, B. (2005). Body in Question:Exploring the CuttingEdge in Forensic Stehr, F.W. (1987, 1991). ImmatureInsects, Volumes 1-2. Dubuque, IA: Science.New York,NY: Sterling Publishing. Kendall-Hunt Publishing. McAlpine, J.F. (1981, 1987, 1989). Manual of Nearctic Diptera, Volumes Triplehorn,C.A. &Johnson, N.F. (2005). Borrerand Delong'sIntroduction to 1-3.Ottawa, Canada: Agriculture Canada Research Branch. the Studyof Insects,7th Edition.Belmont, CA:Thomson Brooks/Cole.

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410 THEAMERICAN BIOLOGY TEACHER, VOLUME 68,NO. 7, SEPTEMBER2006