News Update on Entomology : Dec 2021

Entomology for the copepodologist

Copepods are often called ‘insects of the seas’. Is this justified? Today insects are regarded as the most successful group of animals. Measures of absolute success are phylogenetic age (survival through time), dominance (relative abundance, proportion of total biomass, role in energy flow, impact on ecosystems and coexisting organisms), speciosity, geographic range, and breadth of adaptive radiation. Measured by these criteria copepods are no less successful than insects. What about relative success? There must be intrinsic features in the structure and mode of life of insects which make them more successful relative to other animal groups. According to the literature these features are small size, metamorphosis, wings, and mouthparts. If the capacity to fly is equated with the capacity to swim copepods share all these intrinsic features being equal with insects also in relative success. Entomologists believe insects to be unmatched by other groups in most features of evolutionary success. Yet, they outdo copepods only in one respect: number of species. Reasons for this are greater spatial heterogeneity and architectural complexity (of vegetation) on land than in the sea as well as the fact that insects were among the first groups on land relatively unaffected by other groups, whereas copepods had to evolve in an already crowded world. [1]

A Textbook of Entomology

An account of the early history of entomology and of the development of economic entomology in North America is followed by chapters on the characters of the different Arthropod classes, and on the anatomy, physiology and life-cycles of insects, and then by one in which the main Orders are considered individually. This includes keys to common families and notes on habits, illustrated largely by reference to insects of economic importance in North America. Other chapters are concerned with the geological history of insects and with ecological factors, and a. concluding one contains a general review of the many different types of damage caused by insects and the methods available for their control. [2]

Forensic entomology

Necrophagous insects are important in the decomposition of cadavers. The close association between insects and corpses and the use of insects in medicocriminal investigations is the subject of forensic entomology. The present paper reviews the historical background of this discipline, important postmortem processes, and discusses the scientific basis underlying attempts to determine the time interval since death. Using medical techniques, such as the measurement of body temperature or analysing livor and rigor mortis, time since death can only be accurately measured for the first two or three days after death. In contrast, by calculating the age of immature insect stages feeding on a corpse and analysing the necrophagous species present, postmortem intervals from the first day to several weeks can be estimated. These entomological methods may be hampered by difficulties associated with species identification, but modern DNA techniques are contributing to the rapid and authoritative identification of necrophagous insects. Other uses of entomological data include the toxicological examination of necrophagous larvae from a corpse to identify and estimate drugs and toxicants ingested by the person when alive and the proof of possible postmortem manipulations. Forensic entomology may even help in investigations dealing with people who are alive but in need of care, by revealing information about cases of neglect. [3]

Revamp Studies on Morpho-Histology of the Male Reproductive System of Halys dentatus Fabricious (Hemiptera: Pentatomidae)

Aim: Revamp studies on the morphology and histology of plant bug Halys dentatus F. (Hemiptera: Pentatomidae).

Study Design: Halys dentatus Fab. is acting as pest of many plants, multivoltine in nature, therefore their reproductive cycle observed throughout the year. Hence, the number of reproductive cycles increased the population of H. dentatus to cause harm to plants, therefore there is need to study the male reproductive system of H. dentatus as a part of fundamental studies.

Place and Duration of Study: Entomology Research Laboratory; P.G. Department of zoology,

K.T.H.M. College, Nashik. (MS, India).

Methodology: Adults of H. dentatus (Fab.) were collected, anesthetized with anesthetic ether & embedded in dissecting paraffin wax plate, dissected in insect saline solution (Lum, [13]) using stereoscopic research binocular microscope. The male reproductive system exposed and isolated, fixed in Debocqui’s Bouin’s fixative for 18 hrs., dehydrated (acetone grades), Cleared (xylene; acetone), blocks were prepared, sections were cut on Leica microtome, stained & micro photographed.

Results and Observation:

  • Morphology: The male reproductive system of H. dentatus (Fab.) constitute a pair of testis, pair of vas deferens, seminal vesicles, accessory glands (ectodermal & endodermal) & ejaculatory duct (bulbus & ductus).
  • Histology: Histology of testis of H. dentatus showed the six numbers of testicular follicles with different development zones; the growth zone, the maturation zone and the zone of differentiation. The inner layer of vas deferens and seminal vesicle was composed of cuboidal epithelial cells. The accessory glands are both ectodermal and endodermal in origin. The ectodermal accessory glands are triplate, milky white in colour while mesodermal accessory glands are convoluted bunch of fine tubular structure.

Conclusion: The male reproductive system was studied with reference to revamp morpho-histology; during the year 2009-2011. The anatomy resemble with other pentatomid bug with little difference in vas deference, investing sac and major difference is the testicular follicles are six in number not seven. [4]

Determination of Parasitism Efficacy and Development of Effective Field Release Technique for Trichogramma spp. (Trichogrammatidae: Hymenoptera)

To determine the parasitism efficacy of Trichogramma spp. on the host eggs of Sitotroga cerealella Olivier (Pyralidae: Lepidoptera) and Corcyra cephalonica Stainton (Pyralidae: Lepidoptera) and to develop the effective field release technique for Trichogramma spp., the study was conducted at the IPM Laboratory and Research field of Entomology Division, Bangladesh Agricultural Research Institute, Gazipur, Bangladesh during the period from July to December 2013. Higher parasitism on the eggs of S. cerealella and C.cephalonica was recorded from Trichogramma chilonis Ishii (Trichogrammatidae: Hymenoptera) (85.5%, 93.8% respectively), compared to those of Trichogramma evanescens West (Trichogrammatidae: Hymenoptera) (83.4%, 92.7% respectively). Higher percent adult emergence was recorded from the eggs parasitized by T. evanescens compared to those by T. chilonis. The field release techniques for T. evanescens and T. chilonis on parasitizing the eggs of S. cerealella, C. cephalonica and Leucinodes orbonalisGuenee (Crambidae: Lepidoptera) were also assessed by using paper strip method (released during pupation) and adult release method in both micro-plot and open field conditions. In micro-plot, the results showed that T. evanescens parasitized 75.5% of host eggs (mean of three host eggs) by adult release method and 38.83% only by paper strip method. In case of open field condition, T. chilonis parasitized 78.6% of host eggs by adult release method and 40.2% only by paper strip method. The results indicate that as a field release technique of T. chilonis, the adult release method is superior to paper strip method. [5]

Reference

[1] Schminke, H.K., 2007. Entomology for the copepodologist. Journal of Plankton Research, 29(suppl_1), pp.i149-i162.

[2] Ross, H.H., 1948. A textbook of entomology. A Textbook of Entomology.

[3] Amendt, J., Krettek, R. and Zehner, R., 2004. Forensic entomology. Naturwissenschaften, 91(2), pp.51-65.

[4] Jyoti, G., Santosh, N. and Ashok, D., 2015. Revamp studies on morpho-histology of the male reproductive system of Halys dentatus Fabricious (Hemiptera: Pentatomidae). Annual Research & Review in Biology, pp.176-183.

[5] Chowdhury, Z.J., Alam, S.N., Dash, C.K., Maleque, M.A. and Akhter, A., 2016. Determination of parasitism efficacy and development of effective field release technique for Trichogramma spp.(Trichogrammatidae: Hymenoptera). Journal of Experimental Agriculture International, pp.1-7.

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