The black soldier fly Hermetia illucens (Diptera: Stratiomyidae) as a potential measure of human postmortem interval: observations and case histories

The black soldier fly, Hermetia illucens (L.), has been shown to be a ubiquitous inhabitant of both surface and buried human remains throughout the southern, central and western United States and Hawaii. Unlike most other species of forensically important Diptera, this species frequently dominates bodies in the dry/post decay stage of decomposition. Adults of the black soldier fly appear to initiate oviposition (egg laying) 20 to 30 days postmortem. Even at warm temperatures (27.8 degrees C), subsequent completion of the life cycle can require an additional 55 days. Life history data for H. illucens, when used in combination with data for other cohabiting arthropod species and viewed in the context of local environmental conditions, can provide medicolegal investigators with valuable parameters for estimating the postmortem intervals for badly decomposed remains.

Estimation of Postmortem Interval Using Arthropod Development and Successional Patterns

Insects are frequently the first organisms to arrive at a dead body. By their activities they begin a biological clock that will allow for an estimation of the postmortem interval (PMI). In this publication, the two general approaches to estimation of the PMI using entomological data are reviewed: (a) use of individual species developmental patterns; and (b) use of arthropod succession data. Recent advances in studies of the biologies of various Diptera (flies) have allowed for more accurate estimates, as have recent detailed studies of the roles of various arthropods in the decomposition process. Five stages of decomposition (fresh, bloated, decay, post-decay, and skeletal) are suggested as reference points in the decomposition process. These stages are largely artificial, but serve as convenient references in court situations. Factors that may delay invasion of the remains by arthropods or alter developmental patterns, such as wrapping of the body, climate, or presence of drugs and toxins in the remains, are discussed. A general plan of approach to the estimation of PMI using entomological data is presented.

Preliminary observations of the effects of amitriptyline in decomposing tissues on the development of Parasarcophaga ruficornis (Diptera: Sarcophagidae) and implications of this effect to estimation of postmortem interval

Larvae of Parasarcophaga ruficornis (Fabricius) (Diptera: Sarcophagidae) were reared on tissues from rabbits administered different dosages of amitriptyline to study the effects of this drug on the development of this insect species. The rabbits were given 300, 600, and 1000 mg of amitriptyline via ear vein infusion. No significant differences in rates of larval growth were observed among the colonies. Durations of the larval stage were significantly longer for larvae fed on tissues from rabbits receiving amitriptyline. Larval mortality was observed to be 5.5% for the control colony, but ranged from 40.5 to 57.5% for the test colonies. Durations of the puparial stage were significantly longer for the colonies fed on tissues from the rabbits receiving the 600 and 1000 mg dosages of amitriptyline than for the control and colony fed on tissues from the rabbit receiving the 300 mg dosage. Observed differences in the durations of the larval and pupal stages from the test colonies were sufficient to alter a postmortem interval estimate by up to 77 h, if based on normal developmental patterns for this species at 26 degrees C. Presence of amitriptyline and nortriptyline could be detected in larvae from all colonies fed on tissues from the rabbits receiving amitriptyline using high-performance liquid chromatography (HPLC).

A BASIC algorithm for calculating the postmortem interval from arthropod successional data

A computer algorithm, implemented in the BASIC language, is presented for calculating the postmortem interval (PMI) from arthropod successional data. Entomology-assisted determination of the PMI promises to be a reliable technique in cases of homicide, suicide, accidental death, and unattended death due to natural causes. The program requires, as input, the identity of arthropod taxa recovered from human remains in a death scene investigation and machine-readable data on carrion-associated arthropod taxa and their known successional patterns of activity for the same geographical area. The program performs rapid comparisons of these lists and, on output, calculates an upper and lower estimate of the PMI, identifies the definitive taxa for these limits, and determines if the remaining corpse taxa have known successional patterns that are consistent for this estimate. An alternate output is provided if one or more corpse taxa do not overlap all the others at any single time in the succession. In that event, the user is prompted to recheck the identity of the non-overlapping taxon or taxa or reevaluate the environmental circumstances surrounding the case in question. Results of the analysis are saved to an ASCII file for output to a printer for making paper copies useful for the entomologist's Case Study Final Report. This program may make possible wider use of this technique in law enforcement and medical investigator offices that utilize both forensic entomologist expertise and IBM PCs (or compatible computers).

Preliminary observations of the effect of methamphetamine in decomposing tissues on the development rate of Parasarcophaga ruficornis (Diptera: Sarcophagidae) and implications of this effect on the estimations of postmortem intervals

Larvae of Parasarcophaga ruficornis (Fabricius) (Diptera: Sarcophagidae) were reared on tissues from rabbits administered different dosages of methamphetamine to study the effects of this drug on development of this species. The rabbits were given 37.5, 71.4, and 142.9 mg of methamphetamine via ear vein infusion. From Hours 30 to 60, larvae feeding on tissues from rabbits receiving 71.4 and 142.9 mg of methamphetamine developed more rapidly than larvae from the control colony and those feeding on tissues from the rabbit receiving 37.5 mg of methamphetamine. The time required for pupariation was significantly greater for colonies fed on tissues from methamphetamine-dosed rabbits than for the control. These differences were sufficient to alter postmortem interval estimates based on larval development by up to 18 h and estimates based on puparial development by up to 48 h. The presence of methamphetamine or amphetamine could not be detected in Diptera larvae in this experiment using radioimmunoassay techniques, as there was a nonspecific reaction, resulting in a false positive.

Presence of fecal material in diapers as a potential source of error in estimations of postmortem interval using arthropod development rates

Second instar larvae of the fly Chrysomya megacephala (Diptera, Calliphoridae) were recovered from the diapers of a 16-month-old child abandoned by her mother on Oahu, Hawaii. The development of these larvae indicated a minimum period of 23.5 h of exposure prior to discovery of the child. Larvae of this species of fly are not normally associated with living tissues in Hawaii, but rather with feces and remains during the early stages of decomposition. Had the child in this case died and data not been provided detailing the site of infestation, the postmortem interval estimated would have been significantly longer than was actually the case, because of the development of the larvae inside the diapers of the living child. The need for caution in cases involving deaths of infants, the elderly, and individuals not capable of caring for themselves is stressed.

Effect of carcass size on rate of decomposition and arthropod succession patterns

Decomposition studies were conducted using two carcasses of domestic pigs, Sus scrofa L., 8.4 kg and 15.1 kg in weight, to determine the effects of carcass size on the rate of decomposition, composition of the arthropod fauna, and succession patterns. A total of 46 arthropod taxa were recovered during this study. No size-related differences were observed between carcasses with respect to composition of the arthropod fauna or patterns of succession. A greater number of arthropods were observed attracted to the 15.1-kg carcass, and the rate of decomposition observed was more rapid for the 15.1-kg carcass than for the 8.4-kg carcass. Internal temperatures of the 8.4-kg carcass were more directly related to external ambient temperatures during the fresh and bloated stages of decomposition. During the decay stage, both carcasses generated internal temperatures significantly above ambient temperatures. Following this stage, internal temperatures fell to approximate ambient temperatures during the postdecay and remains stages.

Comparison of insect species associated with decomposing remains recovered inside dwellings and outdoors on the island of Oahu, Hawaii

A comparison of insects collected from 35 cases of decomposing remains on the island of Oahu, Hawaiian Islands (14 from indoor situations and 21 from outdoors), yielded a total of 22 species of insects in 3 orders and 12 families. Of these, five species were recovered in both indoor and outdoor situations. Remains recovered indoors had a greater variety of Diptera larvae associated with them, while remains discovered outdoors had a greater variety of Coleoptera species present. Some species of insects were restricted to remains discovered indoors, while others were found only associated with remains in outdoor situations. Knowledge of the species of insects associated with different habitats may serve to provide information concerning the history of the remains.

Determination of postmortem interval by arthropod succession: a case study from the Hawaiian Islands

A postmortem interval of 34 to 36 days was established for remains recovered on the island of Oahu, Hawaii, based on interpretations of patterns of arthropod succession on the remains. This interval was primarily based on the presence of adult specimens of Philonthus longicornis (family Staphylinidae), mature larvae of Piophila casei (family Piophilidae), and empty puparial cases of Chrysomya rufifacies (family Calliphoridae). Species and developmental stages of two additional Coleoptera species and three additional Diptera species were also present, which was consistent with the estimated interval, although not definitive.

Effect of heroin in decomposing tissues on the development rate of Boettcherisca peregrina (Diptera, Sarcophagidae) and implications of this effect on estimation of postmortem intervals using arthropod development patterns

Larvae of the flesh fly Boettcherisca peregrina (Robineau-Desvoidy) were reared on the tissues of rabbits to study the effects of heroin on the development rates of this species. The rabbits were given 6, 12, 18, and 24 mg of heroin by cardiac puncture. From Hours 18 to 96, larvae feeding on tissues containing heroin (as morphine) developed more rapidly than those feeding on tissues from the control. The time required for pupation was significantly greater for colonies fed on tissues from heroin-dosed rabbits than for the control colony. The differences observed in the rates of development were sufficient to alter postmortem interval estimates based on larval development by up to 29 h and estimates based on pupal development by 18 to 38 h.

Detection of organophosphate poisoning in a putrefying body by analyzing arthropod larvae

Deaths as a result of organophosphate poisoning are usually detected by analysis of body fluids and tissues for the presence of the toxic agent. These procedures present particular difficulties when performed on remains in an advanced stage of decomposition. Malathion poisoning was suspected in a case in which the remains were in an advanced stage of decomposition and the presence of malathion was confirmed by analyses of gastric content and body fat. Two species of fly larvae, Chrysomya megacephala (Fabricius) and Chrysomya rufifacies (Macquart), were present on the remains. A sample of these larvae was analyzed for malathion content. A total of 574 micrograms of malathion was detected in 0.26 g of pooled larvae, or a level corresponding to 2050 micrograms/g of larvae. Presence of organophosphates in arthropod larvae has not been documented previously and the analysis of larvae from decomposing remains may prove a useful technique for detection of these toxicants in decomposing remains.

Estimation of postmortem interval by arthropod succession. Three case studies from the Hawaiian Islands

Three instances of estimation of postmortem interval using computer-assisted entomological techniques on the island of Oahu in the Hawaiian Islands are presented. While postmortem intervals were similar for all cases (4-5 1/2 days), recovery of the remains in differing habitats (xerophytic, mesophytic, and swamp) on the island resulted in significant differences in gross appearance of the remains, which could have resulted in the determination of different postmortem intervals in the absence of entomological techniques.

Forensic entomology in the Hawaiian Islands. Three case studies

Three instances of the use of entomological techniques for the estimation of postmortem interval in homicide cases on the island of Oahu, Hawaiian Islands, are presented. These cases represent differing stages of decomposition and range from 8 to 53 days postmortem.

The genus Speleocola lipovsky (Acari: Trombiculidae) with descriptions of two new species from Venezuela

Speleocola Lipovsky 1952 is redescribed. New species S. clangula off Rhipidomys sp., Venezuela, and S. nolae off Peropteryx kappleri, Venezuela, are described. A key to the 5 included species is given.

Keys to the genera of chiggers of the western hemisphere (acarina: trombiculidae)

Synotpic keys to the 87 genera of chiggers in the Western Hemisphere (Nearctic and Neotropical regions) as well as illustrations to the terminology employed, are presented.