Penultimate Instar Larvae Research Articles

β-Hydroxy- n-butyric acid in the defensive secretion of Papilio aegeus

β-Hydroxy- n-butyric acid has been identified as a component of the osmeterial secretion of the penultimate larval instar of Papilio aegeus.

Tests for Audible and Ultrasonic Sound Production by Stored-Product Insects1

Ten species of stored-product insects were studied for the production of nonincidental sounds. Eight species confused flour beetle, Tribolium confusum Jacquelin duVal; merchant grain beetle, Oryzaephitus mercator (Fauvel); granary weevil, Sitophilus granaries (L.); flat grain beetle, Cryptolestes pusillus (Schonherr); furniture carpet beetle, Anthrenus flavipes LeConte; Trogoderma glabrum (Herbst); tobacco moth, Ephestia elutella (Hubner); and almond moth, Cadra cautella (Walker)-were monitored both in whole colonies over a 24-hour period and individually (adults, pupae, and last or penultimate instar larvae) under conditions of stress. Two spider beetles, Mezium americanum Laporte and Gibbium psylloides (Czempinski), were monitored under conditions of stress. Both audible (1–14.5 kilocycles per second) and ultrasonic (15–60 kilocycles per second) ranges were monitored. A method of determining the minimum discernible signal of a microphone by electronic means is described. No stridulatory or protest (stress) sounds were heard.

Influence of the corpus allatum on the development of internal organs in Galleria mellonella L.

Effects of corpus allatum hormone (JH) on the growth and differentiation of the internal organs of Galleria larvae were investigated. Some of the internal organs develop continuously, others only for a period in each larval instar. They maintain larval form until the second third of the last larval instar or later and then differentiate towards the imaginal form. Differentiation appears as a continuous process of changes based mostly on degeneration of some parts and more profound growth of the others, which may be interrupted at most points by JH. In this way insects with internal organs intermediate between larval and imaginal structure result. The overall growth of the organs continues after hormone application but at a different rate. Slight morphological change in wing disks which appears in the penultimate larval instar may be also prevented by JH.

The effect of corpus allatum hormone on respiratory metabolism during larval development and metamorphosis of Galleria mellonella L.

Specific cycles in oxygen consumption occur in each instar of Galleria. Three types of cycles have been recognized: the first appears in the penultimate larval instar, the second in the last larval instar, and the third in the pupal instar. When the brain-corpora cardiaca-corpora allata complexes were implanted into freshly moulted last-instar larvae, metamorphosis was delayed, and two to five extra larval instars were induced. Such artificial giant larvae developed finally into giant pupae and these formed morphologically perfect giant moths. The extra larval instars retain the first type of oxygen consumption cycle, the last extra larval instars keep the second type, and the giant pupae retain the third type. Thus it follows that both the larval development controlled by the corpus allatum hormone and the metamorphosis proceeding in its absence are distinguished by specific changes in overall metabolism, regardless of the absolute age and size of the specimen. Changes in metabolic activity induced by hormones were found to be closely correlated with the degree of morphogenetic change. It is concluded that the corpus allatum hormone has an indirect effect on metabolism.

THE ROLE OF CHEMOTACTIC STIMULI IN THE FEEDING BEHAVIOR OF SPRUCE BUDWORM LARVAE ON WHITE SPRUCE

The effects of chemical stimuli on the feeding behavior of penultimate-instar larvae of the spruce budworm, Choristoneura fumiferana (Clem.), were investigated, especially in relation to the relative acceptability of staminate flowers, new vegetative shoots, and mature needles of white spruce, Picea glauca (Moench) Voss.Phagostimulants were extracted from the host plant tissues with 80% ethanol. Some substances known to be present in the extracts and some related compounds were investigated individually. The only substances that induced feeding responses in these tests were a number of sugars and the amino acid L-proline.In choice tests ethanol extracts of the staminate flowers were more acceptable than extracts of the shoots, and shoot extracts were more acceptable than extracts of the mature needles.The various host tissues differ quantitatively and qualitatively in the occurrence of some substances that significantly affect feeding behavior. The concentration of total sugars is greatest in the staminate flowers and least in the mature needles. Sugar concentration influenced feeding; the highest concentration encountered in the extracts evoked the greatest response. The difference in response to extracts of the various tissues was not attributable simply to differences in the sugar concentration.Staminate flowers contain much greater amounts of the amino acid L-proline than do the other tissues. Larvae offered a choice of sucrose plus L-proline or sucrose alone fed preferentially on the mixture. Similar but somewhat less pronounced responses were also noted with the related compounds, hydroxy-L-proline and L-glutamic acid.Pungenin occurs in appreciable amounts in mature spruce needles but is absent from, or present only in trace amounts, in new vegetative shoots. This glucoside deterred feeding but the difference in responses of larvae to extracts of the shoots and mature needles was not solely attributable to this effect. Shikimic acid and caffeic acid each stimulated feeding when present in mixture with sucrose. They may influence the differential feeding responses to the shoots and mature needles.

Effect of hormones on growth and respiratory metabolism in the larvae of Pyrrhocoris apterus L. (Hemiptera)

Cyclical changes in growth and respiration occur in each of the larval instars. The cycles are under indirect hormonal control. The activation hormone stimulates digestive functions and so it increases growth and respiration rates at the beginning of each larval instar. The lack of corpus allatum hormone induces metamorphosis, which is followed by a U-shaped metabolical decrease in the second half of the larval instar. Such a U-shaped metabolical decrease, which normally occurs in the last larval instar, may be induced in the penultimate larval instar by allatectomy, or it may disappear from the last larval instar after corpus allatum implantation. The possible physiological significance of the U-shaped metamorphosis curves is discussed. The relationships between growth, hormones, and metabolism in larvae are very similar to those previously found in adult females.