Size Of Nymphs Research Articles

Ingestion rate of the burrowing mayfly Hexagenia limbata as determined with14C

The effects of nymph size and temperature on the ingestion rate ofHexagenia limbata were investigated using14C labelled algae mixed into sediment. Ingestion rate increased with nymph length and temperature. Daily ingestion rates of large 19 mm nymphs burrowing in silt averaged 58 and 192% of the dry body weight at 16° and 21 °C, respectively. Ingestion of seston due to filter feeding in artificial burrows was insignificant compared to that ingested by burrowing nymphs.

Effects of Temperature on Adult Size and Emergence Success ofHexagenia bilineataUnder Laboratory Conditions

ABSTRACT The simultaneous effect of sex, initial size, and temperature on growth rates, adult size, and size at large wing-pad (LWP) stage of Hexagenia bilineata (Say) mayflies was investigated. We found that female nymphs grew faster than males; that growth at the constant temperature of 15°C was significantly less than at 22.5 and 30.0°C; and that smaller nymphs tended to grow faster than larger nymphs over a period of 49 days. Size of nymphs at the LWP stage was significantly related to sex, with females being considerably larger. Within the same initial size groups, all nymphs reared at 30°C were significantly smaller at the LWP stage than nymphs reared at 22.5°C and 15°C. Metamorphosis was not successful at 15°C. Adults reared at 30°C were significantly smaller than those reared at 22.5°C. The nearly synchronous emergence times of nymphs initially in the 13.5-mm and 17-mm size classes at both 22.5 and 30°C, suggested that adult tissue maturation was initiated almost simultaneously in nymphs of those two sizes. The lag in emergence of nymphs at the initial size of 9 mm suggested that a size-dependent threshold for adult tissue maturation exists between 9 and 13.5 mm body length. Finally, while 15°C was too low to permit successful emergence, it did not inhibit adult tissue maturation.

Bionomics of Haplaxius crudus (Homoptera: Cixiidae) 12

Haplaxius crudus nymphs feed and live in the thatch layer and on the roots of St. Augustinegrass, bahiagrass, centipedegrass, bermudagrass, paragrass, yellow nutsedge, broomsedge, foxtail, and other sedges. Secretions from the abdominal wax glands protect the nymphs from wetness, disease, and predators. Average nymph size after each molt at 24°C was 0.80, 1.35, 1.80, and 2.47 mm for 4 respective molts. No differences in size were noted at 30°C. Wingpad development between each molt is a unique characteristic for identifying nymphal age. All nymphal instars developed more rapidly at 30° than at 24°C. Cool temperature (15°C) had an adverse effect on nymph development. Large nymphs survived an extended period without feeding. Eggs were 0.5–0.6 mm in length and 0.15–0.20 mm in width with one blunt end. Parthenogenic reproduction was not observed. The mean life span for adult males on St. Augustinegrass was 7.3 days and 7.8 days for adult females. The mean generation time at 30°C was 52.6 days and 80.8 days at 24°C. The adult H. crudus survived 37 and 50 days on coconut and veitchia palms, respectively. Coconut cultivars differed significantly in numbers of H. crudus attracted. The numbers of adults attracted to palm differed significantly among seasons. H. crudus was found in palms more in the evening hours than in the morning hours.

Effect of Plant Extracts on Survival and Development of Melanoplus differentialis and M. sanguinipes (Orthoptera: Acrididae)1

Extracts of selected plant species were bioassayed by incorporating them into an artificial diet used to rear Melanoplus differentialis (Thomas) and M. sanguinipes (F.). Marked differences in survival and rate of development of grasshoppers were observed. Within species there were no significant differences in sizes of nymphs or adults reared on the different extract preparations. The number of stadia required before completing development varied but was not related to type of diet. Differences in survival and rate of development were not the result of differences in food consumption or digestion coefficient. There was no correlation between efficacy of extracts from a plant species and the rate of ingestion by grasshoppers in the field. The plant extract was not essential for the 1st instar, but deprivation in any later stadia caused decreased survival and slowed development. Definite symptoms preceded death in 62% of the nymphs on diets with the extract withdrawn after any period.

Bioassays of Plant Extracts for Growth-Promoting Substances for Melanoplus femurrubrum (Orthoptera: Acrididae)1

Extracts of selected plant species were bioassayed by incorporating them into an artificial diet used to rear the red-legged grasshopper, Melanoplus femurrubrum (De Geer). Marked differences in survival and rate of development of grasshoppers were observed. There were no significant differences in the sizes of nymphs or adults reared on the different extract preparations. Differences in survival and rate of development were not the result of differences in food consumption or digestion coefficient. There was no correlation between efficacy of extracts from a plant species and the rate of ingestion by grasshoppers in the field.

ACCLIMATION OF OXYGEN CONSUMPTION TO TEMPERATURE IN THE AMERICAN COCKROACH (PERIPLANETA AMERICANA)

1. Oxygen consumption has been studied in cultures of nymphal and adult cockroaches, Peniplaneta americana, that have been maintained at two experimental temperatures (10° and 16° C.) and the control temperature (26° C.) for a period of one to three weeks.2. It has been shown that the oxygen consumption of equal-weight nymphs when measured at 20° C. is higher in animals that have been maintained at the lower temperatures.3. Comparison of cold- (10° C.) and warm-adapted (26° C.) nymphs when measured at a series of temperatures (10° to 25° C.) demonstrates that cold-acclimated animals consume more oxygen per gram per hour than equal weight warm-adapted ones.4. Adult cockroaches show acclimation of their oxygen consumption to temperature. However, there isa differential response with respect to size; small adults acclimate to a greater degree than large ones. Further, all sizes of nymphs show a greater degree of acclimation than all sizes of adults.