Collecting, Rearing and Preserving Arthropods of Forensic Importance Initial Observations l Forensic entomologists must take detailed notes about the condition of the corpse and the crime scene including: l l l l l Stage of decomposition Indications that the body was covered, wrapped, or had other impediments to insect colonization (partial submergence, etc) Observations on locations of insects on, in, or around the body Climatological data including temp. and humidity. Description of environmental conditions (indoor / outdoor, climate-controlled, shading, forested, urban, etc) Where to Collect? l From the crime scene l l l l l From the cadaver From soil surrounding cadaver From enclosed structures (along baseboards, under carpet, air vents, etc) From site after body removal From autopsy room l l Samples from body Carefully inspect body bag What to Collect? 1) Flying arthropods: e.g., adult flies and beetles 2) Crawling arthropods: e.g., adult / immatures around and under corpse (fly larvae – maggots and beetle larvae). Also inspect ground surrounding body - collect largest, and representative samples of others. 3) Puparia - note empty puparia, the color of any puparia, etc 4) Eggs – location - in clumps around eyes, mouth, genitals, wounds 5) Collect or observe the “unusual” e.g., leaves, algae, insect frass, insect signs, also note absence of arthropods. How to Collect? 1) Do collection preparation away from crime scene: take notes, make observations 1st. 2) Collect larvae and adult insects from on, in, underneath cadaver, and from around any sites of obvious trauma. -- collect older or larger larvae, preserve some, rear ~50 or more). -- collect material for potential DNA or chemical testing (See handout and next slide 3) Collect carefully do not damage preserved insects do not harm live insects Sampling the Scene How to Collect? 4) To collect adult insects, use a sweep net to collect both flying insects and insects on vegetation and around body. (from Catts & Haskell 1990) Kill adult insects immediately in insect kill jar with ethyl acetate. Insects (other than adult flies) should be placed in 80% ethanol for storage. Flies are more easily pinned if they are freshly killed How to Collect? 5) Collect larvae in, on, and underneath corpse with soft forceps and either preserve in 80% ethanol (after fixing – I prefer boiling water for 30 s) or save for rearing in maggot motels. 6) Inspect areas around the corpse and collect soil samples for lab analysis with Berlese funnels. Collecting Arthropods The Big Picture Importance of Rearing Insects • Allows FE to confirm insect ID • • More clearly define the PMI • • Adult flies are often much easier to identify than are maggots Rearing to adult allows a definitive developmental point for reference. Provides FE with a valuable database of insect development that can be applied to future cases. Do’s and Don’ts 1) Keep temperatures between 24 - 28˚C and ~70% humidity. 2) Maintain larvae with adequate food supplies. 3) Do not overcrowd insects. 4) *Do not mix samples from different cases 5) Rear different samples separately (head sample, wound sample, etc) 6) Do not mix adult stages with larval stages, especially if some species are predators or cannibals. Maintain adults in containers with screened lids. How to rear flies l Insect rearing can be challenging l l Different species have different requirements (some are easy – Phormia, Calliphora), some are more difficult – Lucilia illustris and L. coeruleiviridis) I use maggot motels in constant temperature environmental chambers. l l Catts and Goff (1990) show the basic motel design. Substitute lean boneless pork chop and sterilized potting soil as a substrate for better success. pork chop How to Preserve Insects? l l Insects collected are evidence!! Proper chain of custody and preservation are critical for it to have any evidentiary value. Larvae / Immatures: (Diptera - maggots). l Need to be fixed for preservation. Placing the living maggot in boiling water for 30 seconds gives excellent results. Store in 80% alcohol in glass vials (4 dram screw cap) l Label with pencil!! l l Adult Insects: (Diptera (flies) and Coleoptera (beetles l l Avoid preserving in liquids if possible pin individuals with identification labels Labeling Samples Take Home Messages Collecting: -- Collect climatological and entomological evidence thoroughly, carefully and abundantly. Don’t skimp on observations about the crime scene and surrounding habitat. Rearing: -- Usually not done by the crime scene tech, but evidence collected for this purpose is critical for the entomologist. Living samples are vital both for identification and for calculating PMI.