J. Aust. ent. SOC.,1983,22 137-148 137 THE SUCCESSION AND RATE OF DEVELOPMENT OF BLOWFLIES IN CARRION IN SOUTHERN QUEENSLAND AND THE APPLICATION OF THESE DATA TO FORENSIC ENTOMOLOGY M. A. O'FLYNN Department of Parasitology, University of Queensland, St Lucia, Qld 4067.* Abstract The succession and rate of development of insects in carrion is potentially a useful and accurate tool for determining the length of time elapsed since death, but the accuracy of this method in Queensland has been severely limited by lack of data. The occurrence of the following species in carrion in the Brisbane district and at a site 450 km west of Brisbane from 1975 to 1979 is discussed: Lucilia cuprina (Wiedemann), Lucilia sericata (Meigen), Calliphora augur (F.), Calliphora stygia (F.), Calliphora hilli (Patton), Chrysomya rufifacies (Macquart), Chrysomya varipes (Macquart), Chrysomya megacephala (F.), Chrysomya nigripes Aubertin, Chrysomya saffranea (Bigot), Hemipyrellia ligurriens Wiedemann, Chrysomya megacephala (F)., Tricholioproctia tryoni (J. and T.), Ophyra spinigera Stein and Australophyra rostrafa (R.-D.). Detailed observations at constant temperatures were made on rate of development of flies commonly infesting human cadavers. The duration of the egg, first and second larval instars, total feeding period, total larval period, pupal period and egg to adult period are given for the following species at the temperatures indicated: L. cuprina (15-34"C), C. augur (9-28"C), C. srygia (9-28"C), Ch. rufifcies (20-34°C) and A. rostrara (9-28°C). Limited data on rate of development of Ch. varipes, Ch. sajranea, Ch. nigripes and Ch. megacephala are also included. The application of these data to forensic entomology is discussed. Introduction The use of blowflies to calculate time of death has been discussed by several authors, notably Megnin (1894), Easton and Smith (1970), Leclercq (1969, 1974,1976) and Nuorteva (1974, 1977). Useful information on succession and rate of development was provided by other authors, particularly Fuller (1934), Johnston and Tiegs (1922), Mackerras (1933), Norris (1959, 1965, 1966) and Waterhouse (1947) in Australia and by Bohart and Gressitt (1951), Deonier (1940), Payne (1965, 1967), Reed (1958), Roy and Siddons (1939) and Wijesundara (1957) overseas. However, the work of these authors was not carried out primarily for forensic purposes and therefore does not include such vital information as the duration of each larval instar. Furthermore, differences in the climate and in the composition of the blowfly populations between Queensland and southern Australia make much of the data from southern Australia inapplicable to the Queensland situation. Research was therefore undertaken from 1975 to 1979 to provide detailed information on distribution, behaviour and rate of development of carrion-breeding blowflies in the field in Queensland and on rate of development under controlled conditions in the laboratory, in order to improve the accuracy of estimates of length of time elapsed since death. Data on rate of development at constant temperatures must be used in conjunction with field data (O'Flynn 1976,1980; O'Flynn and Moorhouse 1979), data on the behaviour and distribution of the species concerned (Norris 1959, 1966; O'Flynn and Moorhouse 1979; Zumpt 1965) and the keys and descriptions of their immature stages (Cantrell 198 1; Fuller 1932; Kitching 1976; O'Flynn and Moorhouse 1980). Materials and methods Observations on animal carrion were carried out at 2 sites in southern Queensland: (I) the University of Queensland farm at Moggill on the outskirts of Brisbane (27" 25'S, 152" 54'E): (2) in grazing country in the Thallon district (28" 303, 148" 57'E), ca 450 km west-south-west of Brisbane. Climatic data (Bureau of Meteorology 1975) for these 2 sites are given in Table 1, the data for St George, approximately 38 km north of Thallon being the closest approximation to that for Thallon. Carcasses of large animals, mainly sheep, pigs and dogs were used for field experiments. When possible, maggots were collected twice daily until no maggots remained on the carcass: however, shorter periods of observation were sometimes unavoidable. As small a sample as possible was collected to avoid disrupting the succession while still giving a representative sample of the maggots present at each site on the carcass; the sample size depended on the abundance of maggots at each site. Larvae were identified by the keys of * Present address: Department of Primary Industry, Edmurrd Barton Building, Barton, A.C.T. 2602. 138 M. A. OFLYNN Kitching (1976) and OFlynn and Moorhouse (1980) but if there was any doubt a number were reared to adults. Information on seasonal abundance, behaviour and development of blowflies in animal carrion was supplemented by observations of blowflies collected from human cadavers from throughout Queensland (Moorhouse and O’Flynn unpub. data). The species found to be the most common were cultured in the laboratory and detailed observations made on their rate of development at constant temperatures. Eggs were collected on liver and larvae reared on “pet mince”, a mixture of muscle and offal obtained from a local butcher. The age of the meat used for rearing was varied according to the preference of the species being reared, although most species could be reared successfully on either fresh or putrid meat. For Ausrralophyra rostrata (R. -D.),the meat in which a generation of Lucdia cuprinu (Wiedemann) had been reared, was used. In the early stages of development, twice-daily observations were made, being reduced to once-daily when the maggots reached the third instar. For each species, observations at each temperature were carried out on 2 batches of approximately 100 eggs, which were culled to approximately 30 larvae; further repetitions were made only if the first 2 sets of data did not agree. Results Succession in field carcasses Data on decomposition and succession in carrion are summarised in Tables 2-4. Time since death is given in days, ‘day 1’ covering the period from death to 24 h after death. The stage described as ‘wandering larva’ is the post-feeding larva of Fraenkel and Bhaskaran (1973). The ‘pupa’ is the stage commencing with the formation of the ‘white pupa’ of Fraenkel and Bhaskaran (1973). The stages of decomposition are described according to the classification of Payne (1965) with the addition of the stage ‘slightly decomposed’. Payne’s stages after ‘advanced decay’ are combined into 1 as the carcass in those stages is not infested by blowflies. These stages are represented in Table 2 as follows: 1x-slightly decomposed, 2x-bloated. 3x-active decay, 4x-advanced decay, 5x-stages after advanced decay. The presence of a particular species on a given day, is indicated by an asterisk. In addition to the species mentioned in Tables 2-3 Tricholioproctia tryoni (J & T) was found as first instar larvae on day 1 in summer and on day 2 in winter; Calliphora hilli (Patton) was found as second instar larvae on day 6 in winter, on 1 occasion only; L.cuprina 0 Ch.rufifacibs r Ch. varipws ’a-0 10 20 30 40 Iu 10 20 30 40 0 OC 0 FIG.1-The relationship between temperature and development from egg to adult for L. cuprina, C. stygiu, C. augur, Ch. rujifucies and Ch. varipes. TABLE1 CLIMATIC DATA AT EXPERIMENTAL SITES Jan Feb Mar APr May June July Aug Sept Oct Nov Dec 8 Si George 6 Rainfall (mm) 73.0 62.0 55.0 30.0 35.0 35.0 33.0 26.0 28.0 38.0 44.0 51.0 Temperature 2 Mean daily % maximum ("C) 34.2 34.2 31.4 28.4 23.0 20.3 19.3 21.0 24.8 29.0 31.9 33.4 Mean daily c minimum ("C) 21.3 21.1 18.7 14.2 9.5 6.7 5.3 7.4 10.6 15.0 17.3 19.8 E Moggill 1 Rainfall (mm) 167.0 212.0 81.0 87.0 96.0 19.0 82.0 53.0 22.0 155.0 137.0 148.0 Temperature Mean daily maximum ("C) 30.1 28.6 28.6 26.9 24.2 21.0 20.8 22.6 24.0 26.7 27.4 28.8 Mean daily minimum ("C) 19.2 19.0 17.0 13.9 11.6 8.8 6.8 8.6 10.3 14.1 14.9 17.4 140 M.A. OFLYNN and Hemipyrellia ligurriens Wiedemann was found once, as first instar larvae on day 2 in summer. All of those species appeared to be rare in the experimental areas. Australophyra rostrata was, however found in several carcasses at Moggill; during winter it was found as third instar larvae from day 8 to day 27, and in summer it persisted for up to 8 w in large carcasses. It also occurred in winter carcasses at Thallon; third instar larvae were found in the rumen contents of a sheep 8 w after death, and in the burned remains of a dog 7 w after death (5.5 w after burning) and first and third instar larvae were found in the creamy flesh of an old sheep carcass. Data derived from laboratory studies at constant temperatures The duration of each stage of development over the range of temperatures for which complete development was observed, are given in Tables 5-7 for Lucifia cuprina, Calliphora augur (F.), Calliphora stygia (F.), Chrysomya ruJifacies (Macquart), Chrysomya varipes (Macquart) and Australophyra rostrata. The relationship between temperature and development from egg to adult for the first 5 of these species is shown in Fig, 1. Tables 5-7 include data for Chrysomya nigripes Aubertin, Chrysomya saJranea (Bigot) and Chrysomyamegacephala (F.), at 28 “Conly. The data in Tables 5- 7 are expressed as follows: “n.d.” means no data were available, “1-4 d” means that the duration of the stage was not known exactly but was between 1 and 4 d, “1 to 4 d” means that the minimum observed duration of that stage was 1 d and the maximum 4 d; the symbol “-” indicates the figure is approximate only, a line extending through 2 or more stages of development indicates that the period stated represents the duration of those stages combined.