The Effects Of Population Density On The Development Of The Red Flour Beetle Tribolium Castaneum Herbst

Population dynamics of red flour beetles, Tribolium castaneum (Herbst) was determined using three different sizes of grain patch (bulk), specifically, small (0.03 kg wheat), medium (2 kg wheat) and large (14 kg wheat), at different temperature profiles. The temperature profiles tested were 21, 25, 30, 35 ̊C, T-decrease (30 ̊C in the first 4 weeks and then decreased 1 ̊C /week to -10 ̊C) and T-increase (21 ̊C in the first two weeks and then increased 1 ̊C /week to 38 ̊C). Three male and three female adults were introduced into each grain patch (bulk) at the start of experiments. Numbers of adults in the grain patch (bulk) were counted every 28 days up to 30 weeks. The population dynamics of the Tribolium castaneum (insect numbers) were strongly influenced by the temperature profiles, storage time and grain patch (bulk) size. The insect population increased after 4 week of introduction inside all the grain patches. Later, the number of both offspring and adults showed drastic variation with respect to temperature and storage time under different patch sizes. The peak number or density of insects also showed variation with time for different temperatures and patch sizes. The peak live adult density was the highest in the small patch at each temperature profile. The peak live adult density in the small patch was 300 ± 50, 673 ± 118, 689 ± 48, 1100 ± 150, 1150 ± 150 and 1133 ± 94 adults/kg at 21, 25, 30, 35 ̊C, T-decrease and T-increase, respectively.

The development, relative retention, and oviposition of the red flour beetle, Tribolium castaneum (Herbst) (Coleoptera: Tenebrionidae), on six different types of starches, wheat flour, and wheat flour plus yeast were investigated in the laboratory. The particle size of starch and flours were different; the mean size of 90% of particles for starches ranged from 15 [Mu]m for high amylose corn starch to 58 [Mu]m for potato, whereas that of the flour was 9́Þ 133 [Mu]m. Larval length, head capsule width, and weight gain of T. castaneum larvae were measured every 3 d on starches, flour, and flour plus 5% (by wt) yeast diet for 30 d at 28oC, 65% r.h., and 14:10 (L:D) photoperiod. Larvae reared on flour and flour plus yeast developed normally and showed better survival compared to those reared on starches. Larvae on the starches failed to develop beyond second, and rarely, third instars. Adults of T. castaneum did not show any preference to flour over starches in dual-choice tests in circular arenas. On average, T. castaneum laid less than 3 eggs/female over a 15-d period on starches compared to 97 and 109 eggs/female on flour and flour plus yeast diet, respectively. These studies suggest that starches are poor substrates for larval survival and development. Starches were as attractive as flour to adults; however, starches do not appear to be a suitable medium for egg-laying. Both aggregation pheromone and volatiles did not trigger oviposition behavior. Experiments by moving adults between wheat starch and wheat flour and vice versa showed that feeding on wheat flour was necessary for egg-laying, indicating the absence of essential nutrients in wheat starch. On wheat flour, feeding for 0.5 d was necessary to lay eggs. Females that were starved failed to lay eggs, reinforcing that the nutrional status of females and not males was essential for egg-laying. A minimum of 4% of wheat gluten (wheat protein) elicited egg-laying on starches, although 4-5 times fewer eggs were laid in starch gluten compared with wheat flour alone. Supplementing wheat starch with 1% cholesterol, in addition, to gluten, did not result in an increase in egg-laying by T. castaneum females. These findings suggest that starches may have potential in managing development and reproduction of T. castaneum--a pest that is common and severe in food-processing facilities. Furthermore, starches can be used as a suitable substrate for studying the nutritional ecology of T. castaneum.

Insect infestations in grains and other stored food and fibre products cause annual losses worth many millions of dollars worldwide. This illustrated guide enables specialists and non-specialists to distinguish the major pests of durable stored products found throughout the world. It describes how to identify each pest group or species and summarises the latest information on their biology, ecology, geographical distribution, the damage they cause and their economic importance. Hundreds of colour photographs illustrate the identifying features of the most important beetles, moths, psocids, bugs and wasps found in stored products. Essential details on inspection and trapping are included to aid in the early detection of infestations, allowing more time to plan and undertake effective pest control. An extensive bibliography provides a convenient entry point to the specialised literature on these insects. This concise yet comprehensive reference is an essential tool for people responsible for the storage and handling of dried durable products of plant and animal origin worldwide.