Medicolegal forensic entomology is the study of insects to aid with legal investigations (Gemmellaro, 2017). Insect evidence can be used to provide information such as the post-mortem interval (PMI). Blow flies are especially useful as these insects are primary colonizers, quickly arriving at a corpse (Malainey & Anderson, 2020). The age of blow flies found at a scene is used to calculate the PMI. Blow fly age can be estimated using weather data as these insects are poikilothermic (Okpara, 2018). Morphological analysis also can be used to estimate age; however, it is more difficult with pupal samples as the pupae exterior does not change significantly as development progresses (Bala & Sharma, 2016). Gene regulation analysis can estimate the age of samples. MicroRNAs are short noncoding RNA that regulate gene expression (Cannell et al., 2008). Here, we aim to catalog miRNAs expressed during the development of three forensically relevant blow fly species preserved in several storage conditions. Results demonstrated that various miRNA sequences were differentially expressed across pupation. Expression of miR92b increased during mid pupation, aga-miR-92b expression increased during early pupation, and bantam, miR957, and dana-bantam-RA expression increased during late pupation. These results suggest that microRNA can be used to estimate the age of pupal samples as miRNA expression changes throughout pupation. Future work could develop a statistical model to accurately determine age using miRNA expression patterns.

In this experiment, the viability of gunshot residue (GSR) was examined. This was done through the very rarely researched intersection of forensic firearms analysis and forensic entomology. The question being resolved is if GSR can reliably be detected from secondary evidence transfer of GSR laden carrion onto flies and their larvae. While it is know that secondary and tertiary GSR evidence can be transferred by way of handshakes, no such research has been conducted on flies or their pupae. Findings indicated varying levels of detection of GSR on evidence. GSR could reliably be detected on fly bodies and their legs, but not on their pupae. This research is significant as it provides previously unknown information on this line of research and provides the groundwork for further research on this topic in the future.

Forensic entomology is an important field of forensic science that utilizes insect evidence in criminal investigations. Blow flies (Diptera: Calliphoridae) are among the first colonizers of remains and are therefore frequently used in determining the minimum postmortem interval (mPMI). Blow fly development, however, is influenced by a variety of factors including temperature and feeding substrate type. Unfortunately, dietary fat content remains an understudied factor on the development process, which is problematic given the relatively high rates of obesity in the United States. To study the effects of fat content on blow fly development we investigated the survivorship, adult weight and development of Lucilia sericata (Meigen; Diptera: Calliphoridae) and Phormia regina (Meigen; Diptera: Calliphoridae) on ground beef with a 10%, 20%, or 27% fat content. As fat content increased, survivorship decreased across both species with P. regina being significantly impacted. While P. regina adults were generally larger than L. sericata across all fat levels, only L. sericata demonstrated a significant (P < 0.05) difference in weight by sex. Average total development times for P. regina are comparable to averages published in other literature. Average total development times for L. sericata, however, were nearly 50 hours higher. These findings provide insight on the effect of fat content on blow fly development, a factor that should be considered when estimating a mPMI. By understanding how fat levels affect the survivorship and development of the species studied here, we can begin improving the practice of insect evidence analysis in casework.

In the 1930s, George Beadle and Boris Ephrussi discovered factors that affect eye colors in developing fruit flies. They did so while working at the California Institute of Technology in Pasadena, California. (1) They took optic discs (colored fuchsia in the image) from fruit fly larvae in the third instar stage of development. Had the flies not been manipulated, they would have developed into adults with vermilion eyes. (2) Beadle and Ephrussi transplanted the donor optic discs into the bodies of several types of larvae, including those that would develop with normal colored eyes (brick red), and those that would develop eyes with other shades of red, such as claret, carmine, peach, and ruby (grouped together and colored black in the image). (3a) When implanted into normal hosts that would develop brick red eyes, the transplanted optic disc developed into an eye that also was brick red. (3b) When implanted into abnormal hosts that would develop eyes of some other shade of red, the transplanted optic discs developed into eyes that were vermilion. Beadle and Ephrussi concluded that there was a factor, such as an enzyme or some other protein, produced outside of the optic disc that influenced the color of the eye that developed from the disc.

Fruit flies of the species Drosophila melanogaster develop from eggs to adults in eight to ten days at 25 degrees Celsius. They develop through four primary stages: egg, larva, pupa, and adult. When in the wild, female flies lay their fertilized eggs in rotting fruit or other decomposing material that can serve as food for the larvae. In the lab, fruit flies lay their fertilized eggs in a mixture of agar, molasses, cornmeal, and yeast. After roughly a day, each egg hatches into a larva. The larva eats the material it finds itself in, and for four days it grows into stages of increasing size, called first-, second-, and third-instar stages. This figure shows a third-instar larva. Each larva has sections of tissue called imaginal discs, from which various parts of the adult anatomy develop. This figure shows the imaginal discs that will develop into antennae (colored purple), eyes (colored red), brain (colored blue), and wings (colored green). After four days, the larva turns into a pupa by making a casing, similar to caterpillars, and grows within the casing. After a four-day metamorphosis, the adult fly then emerges from its pupal casing. Adult males look somewhat different from adult females, as the males have darker rear abdomen segments than do females. The warmer the temperature around the eggs, the faster the flies develop to adults.

This diagram shows the life cycle of Neurospora crassa, a mold that grows on bread. N. crassa can reproduce through an asexual cycle or a sexual cycle. The asexual cycle (colored as a purple circle), begins in this figure with (1a) vegetative mycelium, which are strands of mature fungus. Some of the strands form bulbs (2a) in a process called conidiation. From those bulbs develop the conidia, which are spores. Next, (3a) a single conidium separates from its strand and elongates until it forms mycelium. The sexual cycle (colored as an orange circle) also starts with the (1b) vegetative mycelium. The strands develop into a structure called the proto-perithecium, and reproduction involves the proto-perithecium interacting with the conidia from a different mycelium. Reproduction also involves two mating types, called type A and type a. In reproduction, type A pairs with type a, and a conidium can be of either type, as can a proto-perithecium. A proto-perithecium fertilized by a conidium of the opposite mating type (2b) will develop into a perithecium. Inside the perithecium, croziers develop and mature into asci. (3b) In a maturing ascus, there are two nuclei (one represented as a white circle and one as a black circle), one of which comes from the conidium and the other from the proto-perithecium. Each nuclei has only one set of chromosomes (haploid). The two haploid nuclei fuse into a diploid nucleus (represented as a half black half white circle). The nucleus then divides, separating into two nuclei each with one set of chromosomes. Those nuclei duplicate themselves (represented as two white circles and two black circles), and then all the nuclei duplicate themselves again (represented as four white circles and four black circles). This process yields eight haploid ascospores within a mature ascus. Ascospores are spores, and function for the mold as do seeds for plants. The mature perithecium releases its ascospores (4b), which germinate and grow into mycelium. In the 1930s and 1940s, George Beadle and Ed Tatum collected the spores of irradiated N. crassa to study how genes produced enzymes.

In 1935, George Beadle and Boris Ephrussi developed a technique to transplant optic discs between fruit fly larvae. They developed it while at the California Institute of Technology in Pasedena, California. Optic discs are tissues from which the adult eyes develop. Beadle and Ephrussi used their technique to study the development of the eye and eye pigment. (1) The experimenter dissects a donor larva, which is in the third instar stage of development, and removes the optic disc (colored red) with a micropipette. Because the antenna disc is attached to the optic disc, they are often removed and transplanted together. (2) The experimenter then implants the optic disc into a host larva, in the part of the host that will develop into an adult abdomen. As the host larva matures to adulthood, the implanted optic disc develops into an eye inside the body cavity of the adult. (3) The adult host has an eye within its body, which Beadle and Ephrussi found by dissecting the adult hosts. If the antenna disc was also transplanted, sometimes the resulting eye developed with an antenna attached.

Barbara McClintock conducted experiments on corn (Zea mays) in the United States in the mid-twentieth century to study the structure and function of the chromosomes in the cells. McClintock researched how genes combined in corn and proposed mechanisms for how those interactions are regulated. McClintock received the Nobel Prize in Physiology or Medicine in 1983, the first woman to win the prize without sharing it. McClintock won the award for her introduction of the concept of transposons, also called jumping genes. McClintock conceptualized some genetic material as not static in structure and order, but as subject to re-arrangement and may be altered during development.