Late Instar Nymphs Research Articles

The Influence of Age, Diet and Lipid Content on Survival, Water Balance and Na+ and K+ Regulation in Dehydrating Cockroaches

ABSTRACT In dehydrating conditions late instar nymphs lose weight more slowly and survive longer than adult Periplaneta americana. This appears to be due, at least in part, to the larger lipid stores which are found in the fat bodies of the nymphs. When the water loss from an animal is greater than the amount of metabolic water obtained from the catabolism of stored foods, water is removed from the haemolymph in order to maintain water balance in the tissues. Dehydration for 6 days causes the haemolymph volume to decrease markedly in most adults, but the haemolymph Na+ and K+ concentrations increase only slightly. During dehydration the mean Na+/K+ ratio of the fat body tissue increased in adults, except in those which had been fed on pure carbohydrate prior to dehydration. Although not always statistically significant on account of the large variances, the changes in mean Na+, K+ and in the Na+/K+ ratio suggest there is an increase in Na+ and decrease in K+ in the fat body of animals where the haemolymph volume is markedly reduced by dehydration.

Control of the Pear Psylla with Insect Growth Regulators and Preliminary Effects on Some Non-target Species1

Two insect growth regulators (IGR) ZR-512 (Ethyl 3,7,1l-trimethyldodeca-2,4-dienoate) and ZR-515 (Isopropyl 11-methoxy-3,7,11-trimethyldodeca-2,4-dienoate) were evaluated for their control of the pear psylla, Psylla pyricola Forster, and for their effect on nontarget pear pests and predators. Under laboratory conditions, adult psylla exposed to residues of IGR's failed to lay viable eggs, though the number laid and the general appearance of eggs seemed normal. Adult psylla from late-instar nymphs which were exposed to ZR-515 failed to lay viable eggs. In field tests no direct reduction in adult psylla levels was observed following application with IGR's, but 3 weeks post treatment the ratio of psylla eggs per nymphs was much greater in these plots. The effect of IGR's was minimal on other pest species, and no significant decrease in predator species was noted.

Preferences of the Predator Xylocoris flavipes (Hemiptera: Anthocoridae) for Species and Instars of Stored-Product Insects

Early and late-instar nymphs and adult Xylocoris flavipes (Reuter) were exposed simultaneously to early or late-instar larvae of the Indian meal moth, Plodia interpunctella (Hubner); the red flour beetle, Tribolium castaneum (Herbst); the sawtoothed grain beetle, Oryzaephilus surinamensis (L.); and the cigarette beetle, Lasioderma serricorne (F.). Xylocoris flavipes preyed on early and late instars of all species, but the numbers killed depended partly on the size of the prey and possibly other factors.

BIOSYSTEMATICS OF THE TINGID PARASITE HOLDAWAYELLA IN ONTARIO (HYMENOPTERA: BRACONIDAE, EUPHORINAE)

AbstractHoldawayella juglandis Loan, a new species, and some aspects of the anatomy of the final-instar larva of the only other known species of this genus, H. tingiphaga Loan, are described. Host records and field data are reported for both species for Ontario. Though the adults of the two species are very similar morphologically, H. juglandis lacks parthenogenesis, is restricted to the tingid Corythucha juglandis Fitch that breeds only on species of Juglans L., and has specific phenological characteristics. In both species, the head sclerites of the final-instar larva are typically euphorine, and the abdomen bears 3 unpaired, medial, teat-like appendages on segments 5, 6, and 7 whose function is unknown and which do not seem to have homologues in other insect larvae. Both species are single-brooded, lay their eggs in late-instar nymphs and possibly also teneral adults of Corythucha, overwinter as first-instar larvae in adults of these tingids, and complete their endoparasitic and cocoon development in about 90 days during the following spring and summer so that adults of H. tingiphaga begin to emerge from the soil about mid-July and those of H. juglandis about 8 days later. New host records for H. tingiphaga are C. coryli O. & D., C. heidmanni Drake, and C. ulmi O. & D.

Growth and differentiation of the testes in the large milkweed bug, Oncopeltus fasciatus (Dallas).

AbstractDuring the fourth instar there is a five‐fold increase in testis volume, caused by mitotic proliferation of spermatogonia that leads to accumulation of many layers of cysts of resting spermatocytes. At the beginning of the fifth instar the basal cysts undergo meiotic division, and a wave of meiosis followed by spermateleosis progreses apically. There is little or no spermatogonial multiplication; the three‐fold increase in testis size involves primarily spermatocyte differentiation. The wave of differentiation continues at a slower rate in the young adult; most of the spermatocyte cysts are transformed into about 250,000 spermatozoa by the twelfth day. Multinucleate apical cells that stain deeply with Feulgen reagent are present in the early fourth instar, enlarge in the fifth, and persist in the adult testis.Spermatocyte differentiation is not affected by treatment of nymphs with a synthetic juvenile hormone to analog during the fourth or fifth instar, although the treatment causes moderate to high juvenilization at the metamorphic molt. Since late fourth‐instar testes transplanted into mature male or female adults also undergo extensive transformation of spermatocytes into spermatozoa, molting is not required for differentiation. Treatment of late fourth or early fifth instar nymphs with the chemosterilant tretamine causes high mortality at the metamorphic molt, but the wave of spermatocyte differentiation during the fifth instar proceeds normally, although there is evidence of severe chromosome damage.Comparisons with development in the female of Oncopeltus and in other insect species suggest that there is a profound change in the biochemical milieu at the molt from fourth to fifth instar, many processes preceding this molt tending to be larval in character and to diminish or disappear afterward while processes normally occurring after the molt tend to be adultoid.

Big-Eyed, Geocoris spp. (Insecta: Hemiptera: Lydaeidae)

Big-eyed bugs are small insects (approximately 1/6 inch long) that occur in many parts of the world. They are generally regarded as beneficial because they prey upon numerous kinds of insect and mite pests of turf, ornamental and agricultural crops. Big-eyed bugs are among those insects receiving research attention in Florida (and elsewhere) for their value as predators. To aid in identification of big-eyed bugs in Florida, a key to adults and late instar nymphs is provided in this publication. This document is EENY-252 (originally published as DPI Entomology Circular 121), one of a series of Featured Creatures from the Entomology and Nematology Department, Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida. Published: November 2001. Revised: October 2004. 
 EENY252/IN517: Bigeyed Bugs, Geocoris spp. (Insecta: Hemiptera: Geocoridae) (ufl.edu)

Nerve regeneration in the cockroach, Leucophaea maderae: the effect of humoral substances in vitro.

An in vitro system was used to study the effects of diffusible substances from various endocrine tissues on the growth of nerve tissue from regenerating cockroach legs. Incubates prepared from endocrine glands and gland combinations were tested for their effect on regenerative growth from the stump of the fifth mesothoracic nerve of 8-day leg regenerates from late instar nymphs of Leucophaea maderae. Incubates prepared from the prothoracic ganglion produced a stimulatory effect, while the prothoracic gland, allatum-cardiacum complex, and brain showed no effect. When prothoracic gland and prothoracic ganglion incubates were combined, the results were the same as with ganglion incubate alone. When the glands were incubated together and allowed to interact, the nerve growth stimulating effect of the ganglion was reduced by 50%. To explain these findings, it is postulated that a diffusible substance is released by the prothoracic ganglion which stimulates regenerative nerve growth from the leg regenerate. The...

PARATHION ACTIVATION ENZYMES IN THE FAT BODY MICROSOMES OF THE AMERICAN COCKROACH.

Activation of parathion was studied as an example of microsomal oxidation by using the fat body enzymes of 3- to 4-month-old female American cockroaches, Periplaneta americana (L.). Activation was estimated manometrically by inhibition of house fly, Musca domestica L., head cholinesterase. The anticholinesterase product was identified as para-oxon. Purified parathion gave no inhibition of the cholinesterase when assayed in low light. No activation was detected with fat body homogenates from late instar nymphs. The activation enzymes were present primarily in a subcellular fraction that resembled mammalian liver microsomes. The enzymes required oxygen and NADPH2 for activation. NADH2 was a less effective cofactor. Oxidized forms of the cofactors and tetrahydrofolic acid were without effect. The optimum pH for the stability of the enzymes was 7 and that for the activation reaction was 7.5. Loss of para-oxon owing to the microsomes was prevented by pretreating them with para-oxon. Heated microsomes contained a heat-stable factor that supported the reaction. The enzymes were apparently inactivated by the activation reaction. Possible causes were discussed. Activation was inhibited by WARF antiresistant, sesamex, and other insecticide synergists. The mode of inhibition was examined. A nonenzymatic model reaction also was studied.

Predation by birds in relation to the population density of cardiaspina albitextura (Psyllidae)

Field observations suggest that in areas in which the numbers of Cardiaspina albitextura remained low, birds tended to destroy an increasing percentage of late instar nymphs and adults with increase in psyllid numbers. However, when other environmental influences strongly favoured psyllid multiplication, birds were unable to prevent increase to the outbreak level. The response of birds to change in psyllid numbers was functional (not numerical), and depended partly on factors other than psyllid density. In areas in which C. albitextura maintained a high mean level of population density, the percentage destruction due to birds tended to vary inversely with psyllid numbers.

The influence of predation by Syrphus Sp. on the numbers of Cardiaspina albitextura (Psyllidae).

Field observations have shown that the larvae of an unnamed species of Syrphus (closely related to S. viridiceps) are predacious on late instar nymphs of C. albitextura, the fifth (final) instar nymph being the stage attacked most heavily. It was found that Syrphus larvae killed up to about 35% of third to fifth instar nymphs. However, because of the overriding influence of other factors, the mortality caused by Syrphus played only a minor part in the determination of psyllid abundance.

Effect of Infestation by the Rice Stink Bug, Oebalus pugnax, on Yield and Quality in Rice1

Studies were conducted during 1960 and 1961 to evaluate effects or rice stink bug ( Oebalus pugnax (F.)) infestations on rice in Louisiana. Five varieties of rice grown under screened cages were infested during the early heading stage with adults and late-instar nymphs. Infestation levels were varied to determine effect on quality and yield. Quality was affected to the extent that federal support prices for four varieties were reduced even at the lowest infestation which averaged between seven and eight stink bugs per 1,000 panicles. Consistent and severe losses in yields resulted from infestations which averaged approximately 230 or more bugs per 1,000 panicles. Viability of kernels was lowered by injury resulting from stink bug feeding. Greatest reductions occurred in damaged kernels which were injured in the germ region or which were severely atrophied.

Myzus certus (Wlk.), an Efficient Vector of Potato Virus Y

There seems to be only one report of the aphid Myzus certus (Wlk.) transmitting a virus, bean yellow mosaic virus (Swenson, 1957). It is therefore noteworthy that M. certus transmits potato virus Y as readily as does Myzus persicae (Sulz.), until now the most efficient vector known for virus Y. In one experiment that showed this, the numbers of single aphids out of 50 that transmitted virus Y were 27 and 28 respectively. Briefly the experiment was as follows: M. certus was reared on pansy (Viola tricolor) and M. persicae on rape (Brassica napus); the strain of virus Y was the one that has been used at our laboratory for aphid transmission studies during the past ten years; single adult apterae or late instar nymphs each probed once for less than a minute into an infected tobacco plant and then fed overnight on a young healthy tobacco plant (Nicotiana tabacum var. White Burley).

Giant fibres in dragonfly nymphs.

A PRELIMINARY study of transverse and horizontal sections through the ventral nerve cord of late instar nymphs of Anax imperator (Anisoptera) has revealed several notable features. Accurate counts of the number of fibres within the commissures have shown that these range continuously from 0 to 16 µ, as set out in the accompanying histogram (Fig. 1). The total number of fibres is approximately the same for the two commissures. Measurements of axon diameters show that some of the larger fibres (12–16 µ) are comparable with the ‘giant’ fibres of the cockroach1 and locust2. As in the nerves to the stellate ganglia of Sepia3, these fibres form part of a continuous size spectrum and do not appear to differ in nature from the smaller ones. The ‘giant’ fibres are almost certainly the same as fibres a, b and c described by Zawarzin4 in his classical studies of Aeschna nymphs using a methylene blue technique. The ‘giant’ fibres pass through all the abdominal ganglia and send off collaterals into the neuropile of each. Their course through the closely associated metathoracic and first abdominal ganglia to the other thoracic ganglia is more complicated, and has not been fully traced as yet.