School of Life and Environmental Science, Deakin University, 75 Pigdons Rd, Waurn Ponds, 3217, Australia.
Forensic Sci Int. 2024 Oct;363:112170. doi: 10.1016/j.forsciint.2024.112170. Epub 2024 Aug 2.
Chrysomya rufifacies (Diptera: Calliphoridae) is a blow fly species of forensic importance, documented to have a strong preference for colonisation of substrate already inhabited by heterospecific blow fly larvae, thus exhibiting secondary colonisation behaviour. Larvae exhibit predatory behaviour that may be useful to support development where food substrate is limited or high competition exists, but they may alternately be drawn to pre-colonised substrate to capitalise on the advantages of collective exodigestion by previous/current colonisers. Previous authors have suggested female Ch. rufifacies may use visual orientation to detect substrate currently colonised by heterospecific larvae, rather than chemoreception of volatile organic compounds (VOCs), that signify condition of substrate, which would infer that active colonisation is likely a more important oviposition cue for Ch. rufifacies than substrate condition. This study addressed attraction as well as oviposition, examining whether the condition of substrate (either previously colonised or never colonised) or the presence of heterospecific larvae was more important in the initial choice of food source by female Ch. rufifacies where conspecifics were not present, and whether the condition of substrate and presence of heterospecific larvae affects the number of offspring deposited by a female. Attraction was studied using a Y-olfactometer system, and oviposition using a binary-choice assay, with females responding to pairwise choice between an array of meat conditions (fresh, larval aged or aged) and presence/absence of Lucilia sericata larvae. Females displayed a hierarchy of choice of larval aged substrate > aged substrate > fresh substrate, with the active presence of heterospecific larvae a secondary factor in choice. Females produced higher offspring numbers on meat that was either currently or previously colonised by heterospecific larvae, demonstrating the importance of heterospecific indicators of previous or current colonisation as an oviposition cue. This serves as an important consideration for entomologists working with Ch. rufifacies in any capacity where other blow fly species may be present, and most importantly for forensic entomologists where time of colonisation is utilised to estimate PMI.
红头丽蝇（双翅目：丽蝇科）是一种具有法医学重要性的麻蝇物种，有强烈的偏好已被异种蝇幼虫占据的基质殖民化的记录，因此表现出次生性殖民行为。幼虫表现出捕食行为，在食物基质有限或存在高竞争的情况下可能有助于支持其发育，但它们也可能被吸引到预先殖民化的基质上，以利用先前/当前殖民者集体外消化的优势。先前的作者已经提出，雌性红头丽蝇可能使用视觉定向来检测异种幼虫当前占据的基质，而不是通过挥发性有机化合物（VOCs）的化学感受来检测基质的状态，这表明基质的状态表明主动殖民化可能对红头丽蝇比基质状态更重要。本研究研究了吸引力和产卵，考察了在没有同种个体存在的情况下，基质的状态（先前殖民化或从未殖民化）或异种幼虫的存在对雌性红头丽蝇最初选择食物源的重要性，以及基质的状态和异种幼虫的存在是否会影响雌性产卵的数量。使用 Y-嗅觉计系统研究了吸引力，使用二元选择测定法研究了产卵，雌性对新鲜肉、幼虫老化肉或老化肉与丽蝇幼虫存在/不存在的一系列肉条件之间的成对选择作出反应。雌性表现出幼虫老化基质>老化基质>新鲜基质的选择层次，异性幼虫的主动存在是选择的次要因素。雌性在当前或以前被异种幼虫殖民的肉上产生更高的后代数量，这表明异种幼虫指示先前或当前殖民化作为产卵线索的重要性。这对于任何情况下可能存在其他丽蝇物种的从事红头丽蝇工作的昆虫学家来说是一个重要的考虑因素，对于法医昆虫学家来说最重要的是，殖民化时间用于估计 PMI。
