Thermal summation model and instar determination of all developmental stages of necrophagous beetle,Sciodrepoides watsoni(Spence) (Coleoptera: Leiodidae: Cholevinae)

Abstract

Necrophagous beetles are underrepresented in forensic entomology studies despite their undeniable utility for the field. In the present article, information is presented regarding the developmental biology and instar determination of Sciodrepoides watsoni (Spence, 1813), a very common species occurring across the Holarctic region. Wild collected beetles were kept in climate chambers at constant temperature (12, 15, 18, 21 and 28 °C) and their development was regularly documented. Parameters of thermal summation models and standard errors were calculated for each developmental stage. These models may be used for an estimation of post-mortem interval in legal investigations after further validation on local populations of S. watsoni. An additional methodology is introduced for future studies of size-based characteristics, addressing instar identification bias. The methodology provided estimations (mean, standard error and standard deviation) of S. watsoni larval head capsule width for preliminary larval instar determination. The methodology may be used with other morphological features to improve instar determination accuracy.

Temperature models of development for Necrodes littoralis L. (Coleoptera: Silphidae), a carrion beetle of forensic importance in the Palearctic region

“…Models were created also for four species of Dermestidae : populations from south-western Europe of Dermestes frischi, D. undulatus and D. maculatus and Chinese population of D. tessellatocollis 41 , 42 . Developmental models were also published for central European population of Sciodrepoides watsoni (Leiodidae: Cholevinae) 43 , Chinese 44 and central European 45 populations of Creophilus maxillosus (Staphylinidae) and Chinese populations of Necrobia rufipes (Cleridae) 46 and Omosita colon (Nitidulidae) 47 . Although there are beetle taxa that were extensively studied (e.g.…”

Development of larvae of the Australian blowfly,Calliphora augur(Diptera: Calliphoridae), at constant temperatures

“…While measures based on length and weight are valuable, developmental duration is the most widely used method of age estimation for two primary reasons; 1) because the duration of each stage of larval development (referred to as 'instars') is less variable than larval size (particularly in response to differences in diet) 5 ; and 2) because instar stage is not affected by specimen shrinkage during preservation 6 . Once these measurements are obtained for the entire period of larval development, a variety of models can be used to estimate mPMI; including curvilinear regression 8 , isomegalen and isomorphen diagrams 9 , and thermal summation models 10,11 .…”