First Comprehensive Study of a Giant among the Insects, Titanus giganteus: Basic Facts from Its Biochemistry, Physiology, and Anatomy

Abstract

Titanus giganteus is one of the largest insects in the world, but unfortunately, there is a lack of basic information about its biology. Previous papers have mostly described Titanus morphology or taxonomy, but studies concerning its anatomy and physiology are largely absent. Thus, we employed microscopic, physiological, and analytical methods to partially fill this gap. Our study focused on a detailed analysis of the antennal sensilla, where coeloconic sensilla, grouped into irregularly oval fields, and sensilla trichoidea were found. Further, the inspection of the internal organs showed apparent degeneration of the gut and almost total absence of fat body. The gut was already empty; however, certain activity of digestive enzymes was recorded. The brain was relatively small, and the ventral nerve cord consisted of three ganglia in the thorax and four ganglia in the abdomen. Each testis was composed of approximately 30 testicular follicles filled with a clearly visible sperm. Chromatographic analysis of lipids in the flight muscles showed the prevalence of storage lipids that contained 13 fatty acids, and oleic acid represented 60% of them. Some of our findings indicate that adult Titanus rely on previously accumulated reserves rather than feeding from the time of eclosion.

Insects as Food in Aotearoa New Zealand

“…showing highly unusual antennal ultrastructures when compared to other cerambycid subfamilies. The antennae of both sexes of P. reticularis were covered in the sensory pits reported in the other two prionines studied (Dvořáček et al, 2020;Haddad et al, 2023) and contained a sensillum similar in structure to the sensilla described variously as coeloconica (Dvořáček et al, 2020) and unidentified prionine sensilla (Haddad et al, 2023). I agree that there are differences to the sensilla basiconica found in other cerambycid subfamilies (Haddad et al, 2023) but suggest that these are likely still sensilla basiconica with two subtypes identified -thin and broad.…”

“…I agree that there are differences to the sensilla basiconica found in other cerambycid subfamilies (Haddad et al, 2023) but suggest that these are likely still sensilla basiconica with two subtypes identified -thin and broad. The sensilla in the sensory pits were typically surrounded by two to three corrugated, semi-circular glandular openings that are seen in other prionines, although the function of these is unknown (Dvořáček et al, 2020;Haddad et al, 2023). It has been suggested that sensilla chaetica may be absent in the Prioninae (Dvořáček et al, 2020) however I found examples of several sensilla chaetica subtypes on both male and female antennae.…”

“…There are a paucity of studies in the literature of antennal ultrastructures in prionines with only males from two species, Titanus giganteus and Prionus imbricornis, being imaged using scanning electron microscopy (SEM) (Dvořáček et al, 2020;Haddad et al, 2023). Both studies found the sensilla in prionines to be markedly different to other cerambycid sub-families with an absence of sensilla chaetica and the presence of an unidentified sensilla resembling sensilla basiconica but unlike those found in other cerambycid groups.…”

Floral Resources Enhance Fecundity, but Not Flight Activity, in a Specialized Aphid Predator, Hippodamia convergens (Coleoptera: Coccinellidae)

“…Our results indicate that H. convergens adults do not require access to sugar to fuel flight, but likely rely upon stored lipids, as do most other insects (Arrese and Soulages, 2010;Toprak, 2020). Some of these lipid reserves may be accumulated during larval development, and in the case of some Coleoptera, almost entirely (e.g., Tussey et al, 2018;Dvoracek et al, 2020), thus rendering adults less dependent on floral resources. This could be adaptive for H. convergens, given that adult beetles may need to make long distance migratory flights across landscapes where flowers are unavailable, such as after emergence from hibernation or aestivation (Hagen, 1962).…”

Field evaluation of UAV‐based tracking method for localization of small insects

“…First, we quantified the size of insects to clarify the tracking target. One of the largest insects in the world, titanus giganteus, measures about 15 cm and has been recorded up to 16.7 cm (Dvořáček et al 2020). We quantify the size of an insect by quartering its size.…”