Pupation Success Research Articles

Resource- and Density-Dependent Development in Tree-Hole Mosquitoes

Populations of the tree-hole mosquitoes Aedes geniculatus and A. triseriatus were cultured at different food levels and larval densities to determine the fitness consequences of variation in these factors for each species. A composite fitness index and four fitness correlates were calculated for each population. Response-surface regression analysis of these indices indicated that the two species have fundamentally different responses to food and density: The interaction and quadratic effects of these factors had a strong influence on fitness in A. triseriatus but little impact in A. geniculatus. In both species, the composite fitness index was most sensitive to male and female pupal weight, less sensitive to sex ratio and development time, and least sensitive to pupation success. The response-surface model explained over 90% of the variation in fitness in A. triseriatus, but only two-thirds of that in A. geniculatus. We suggest that A. triseriatus is more homeostatic and A. geniculatus more polymorphic for fitness traits, and predict that life-history characters will have higher heritabilities in A. geniculatus than in A. triseriatus.

Density-Dependent Population Growth and Natural Selection in Food-Limited Environments: The Drosophila Model

The action of density-dependent population growth is modeled through the effects of limited food. Scramble competition for food affects viability and adult size, which are correlated with the fecundity of females. Adult effects on fecundity are also explicitly modeled. In the two submodels considered, changes in the minimum amount of food necessary for successful pupation lead to (1) changes in the minimum size of an adult with no change in overall efficiency or (2) constant minimum size but changes in the efficiency of food use. The resulting population dynamics of the two submodels are qualitatively different. For both submodels, population stability requires some degree of adult effects on female fecundity for parameter values typical of Drosophila. When genetic variation is present for competitive ability and minimum food required, natural selection at equilibrium population size favors increasing competitive ability and decreasing the minimum food requirement. Evolutionary changes in the competitive ability of a population do not affect equilibrium population size. Decreases in the minimum food requirements typically increase the equilibrium adult population size but have variable effects on equilibrium egg numbers, depending on the submodel examined. Biological evidence suggests that competitive ability and minimum food requirements may be positively correlated. Genetic models with this antagonistic pleiotropy can maintain allelic variation without overdominance in either character. Furthermore, contrary to established verbal theory, there is no consistent prediction concerning the evolution of average body size. An advantage of this theory is that parameters of interest may be easily estimated in laboratory populations of Drosophila.

Laboratory Studies of Honeybee Larval Growth and Development as Affected by Systemic Insecticides at Adult-Sublethal Levels

SummaryThe effects of two systemic insecticides, carbofuran and dimethoate, at concentrations sublethal to adult worker honeybees (<1·25 μg/g food) on larval growth, pupation success and acetylcholinesterase (AChE) activity were investigated in worker larvae reared on royal jelly (RJ) in the laboratory. Larvae initially exposed to either insecticide at 5 μg/g RJ at a late age (e.g. 96 h) gained weight more slowly than control larvae and died relatively early. Insecticide concentrations of 1·25 μg/g rarely disrupted growth of larvae first exposed at 72–96 h of age. Concentrations sublethal to adults sometimes rcduced mature weights of larvae first exposed at an early age (44 h). Rcduced numbers of potentially viable pupae resulted when these larvae were exposed to carbofuran at 1·25 μg/g or dimethoate even at 0·313 μg/g. As activity of AChE in homogenstes of untreated larvae was highly variable, AChE activity does not appear to be as reliable a criterion for detecting insecticide poisoning of larvae as red...

Comparison of Chemical Effectiveness by the Multinomial Logit Technique

The probabilities of four types of effects when three types of chemicals (pyrethroid, benzoylphenylurea [BPU], and juvenile hormone analogue [JHA]) were sprayed on fourth- or sixth-instar western spruce budworms (Choristoneura occidentalis Freeman) were compared with a multinomial logit model. Our results demonstrated that the BPU’s (triflumuron and diflubenzuron), the pyrethroids (fenvalerate and permethrin), and the JHA methoprene differed in effectiveness (death before pupation, successful pupation with no further development, emergence of an adult with major abnormalities or formation of an adult that did not fully eclose, or successful adult emergence) depending on the effect assessed, the concentration applied, and the developmental stage of western spruce budworms upon which the chemical was sprayed. Use of a scaling procedure permitted comparison of effectiveness patterns without the factor of chemical concentration. The patterns of the two BPU’s applied to fourth instars were the same, as were the patterns for the two pyrethroids. The patterns for the two pyrethroids applied to sixth instars were also the same. However, the patterns for the two BPU’s applied to sixth instars differed significantly. Uses of the multinomial logit model for investigations of chemical modes of action are described.

Long-term effects of Bacillus sphaericus on Culex quinquefasciatus

Initial 48-hr exposures of second-instar Culex quinquefasciatus larvae to 0.005 mg/liter of Bacillus sphaericus primary powder resulted in an average of 58% corrected mortality. Continued significant mortality was observed after the exposures were terminated resulting in an average of 84% cumulative preadult corrected mortality. Successful pupation in surviving treated individuals was significantly delayed. When 84% of the 6-day-old control larvae had pupated, only 25% of the surviving treated group had pupated. There was a significant difference in the survival rates of control adults and those of the treated group. There were also significant differences in the amount of stored nutrients between the two groups. The practical implications of continued mortality, delayed pupation, reduced longevity, and nutrient reserves are discussed.

Screening Potato for Resistance to Potato Tuberworm1

From 3,747 accessions of primitive cultivars and 452 accessions of wild potato species screened for resistance to Phthorimaea operculella (Zeller), 22 primitive and 21 wild potato accessions were identified as highly resistant. These accessions were found resistant to both tuber damage and successful pupation and are now being used in breeding resistance into potentially high-yielding potato varieties adapted to lowland tropics. Resistance is attributed to antibiosis.

Effects of the Insect Growth Regulator Hydroprene on Diapausing Microctonus aethiopoides 1 a Parasite of the Alfalfa Weevil 234

Hydroprene terminated Microctonus aethiopoides Loan diapause when topically applied to host Hypera postica (Gyllenhal). Concentrations of 1, 5, 10, or 50 μg/host terminated diapause in at least 97% of the parasites. Parasite survival and morphological condition were influenced by hydroprene concentration. One μg had no adverse effects other than 8% deformed adults and had no carry-over effect on F1 generation. Five μg did not affect pupation or adult eclosion but caused 31% deformed adults and some deformed adults in F1 generation. Ten μg did not affect pupation, reduced adult eclosion, caused 82% deformed adults, and had a carry-over influence on the Fl generation where there were fewer parasitized weevils, decreases in adult eclosion, and increases in number of deformed F1 M. aethiopoides adults. Fifty μg decreased successful pupation and caused 100% pupal mortality.

Larval growth of some calliphorid and sarcophagid Diptera

AbstractThe competitive abilities of seven calliphorid and one sarcophagid species were examined by investigation of various Characteristics of their larval growth curves. The relative success of each species is thought to depend to a great extent on the ability of the larvae to attain quickly the minimum weight for viable pupation. The ovoviviparous species (Calliphora nociva Hardy, C. augur (F.) and Parasarcophaga crassipalpis (Macq.)) were found to have the most rapid growth and Chrysomya megacephala (F.), Calliphora nociva and C. augur the highest assimilatory rate during the period of most rapid growth. Further, C. nociva, C. augur, Ch. megacephala and Ch. rufifacies (Macq.) were the species best adapted to pupation at low larval weight, which suggests that their food requirements for successful pupation were less (relative to maximum larval weight) than those of the other species. In this respect, Lucilia cuprina (Wied.) was also well–adapted and Ch. varipes (Macq.) was the least successful species.

Aspects of the biology of Staphylinus olens (Müller), Britain's largest Staphylinid beetle

Abstract Methods for rearing Staphylinus olens (Müller) (Col., Staphylinidae) are described, and development compared with other species of Coleoptera. The distribution of S.olens over an area of Manchester is noted, and biological comparisons made with a laboratory population from South Wales. In the area sampled, most individuals live on well‐drained soils, possibly because successful pupation occurs under dry conditions. ‘Courtship’ and mating are described. Egg‐laying, the egg, and its hatching are described, and compared with other coleopteran eggs. Headwidths of laboratory larvae were recorded, and are compared with those of other beetle larvae. Instars I and II lasted 44–45 days, although first instar larvae which eventually pupated had a mean duration of 33.5 days. Instar III averaged 102 days, but this time became shorter with later hatching, roughly synchronizing adult emergence. Pupation and the obtect pupa are described. Pupal development took 32–37 days, after a 10–14 day prepupation period. Newly emerged adults may construct winter burrows after autumn breeding. Second season adults may not hibernate, and often fail to survive another winter. Food is manipulated by mandibles and legs, but no solids are consumed. Adults and larvae will eat many foodstuffs.

Growth and critical size at pupation for larvae of the screwworm developing in fresh wounds.

The growth of larvae of Cochliomyia hominivorax (Coquerel) in fresh wounds on sheep occurred in 3 phases. The lst phase (initial growth) was characterized by a slow increase in weight (from 0.3 to 11 mg) and was terminated after about 84 hours of feeding. The 2nd phase (critical growth) was characterized by attainment of the weight necessary for successful pupation (about 35–65 mg) and was terminated at about 120 hours after infestation, The third phase (postcritical growth) was characterized by an additional increase in weight beyond the critical weight that determined the size of the subsequent adult body; it was terminated by the migration of the larva from the wound (168–196 hours after infestation). Female flies from larvae weighing less than 40 rug after about 96 hours of feeding were frequently delayed in or were incapable of maturing eggs, However, the percentage with retarded ovarian development declined among flies from larvae weighing more than 56 mg after about 96 hours of feeding.

XV.—Observations on the Life Cycle and Immature Stages of Culicoides circumscriptus Kieff. (Diptera, Ceratopogonidæ).

SynopsisThe immature stages of C. circumscriptus Kieff. are found in the mud of most Scottish salt marshes. The life cycle has been studied by means of laboratory cultures and by observation and periodic sampling at a salt marsh near Dumbarton. Data are given concerning the life cycle in the laboratory and out of doors. In the field there are two generations a year.In captivity the female lays a single large batch of eggs which adhere to the substrate by means of structures on the chorion. The eggs and the manner of oviposition and hatching are described. Descriptions of the larvae, supplementing those of previous authors are given. The first instar differs from older larvae in possessing a retractable prothoracic proleg, and is more sluggish in its movements, probably remaining near the oviposition site until the first ecdysis. Before pupation the larva comes to the surface. This is necessary for successful pupation, enabling the pupa to breathe and to form the buoyancy space. The pupa buries itself in the mud emerging only under flooded conditions to float on the surface or prior to ecdysis.

THE BRONZE BIRCH BORER AND ITS RELATION TO THE DYING OF BIRCH IN NEW BRUNSWICK FORESTS

Most of the literature regarding the bronze birch borer discusses the insect as a pest of ornamentals. References to its activity in the forest suggest that it becomes numerous only on cut-over lands where the birch is already moribund from exposure and injury.During the past five years, yellow, white, and grey birch throughout most of New Brunswick have been dying in large numbers from the top down. In 1939 the typical mature yellow birch stand showed about 20 per cent of the trees dead and 35 per cent with over half the crown dead. Young stands were much less severely injured. Virgin stands showed almost as much damage as cut-over lands.Agrilus larvae or galleries were present in practically all injured branches. Some trees were found, however, with the early symptoms of weak foliage growth in the top and no borer attack. Occasional trees occurred with some dead branches and little or no borer attack. No evidence has yet been discovered of the presence of any other destructive organism likely to be the primary cause of death.The question, of the relation of the borer to the observed damage is discussed and the following general conclusions are drawn:(a) The young larvae need living cambial tissue but the development of the final stage to successful pupation is dependent on the death or the moribund condition of the part attacked.(b) Trees of almost all ages, growing normally and apparently healthy, can be attacked and the larvae can develop in them to a half-grown stage. If the attack is sufficiently heavy to bring about the dying of the branch at this stage, development may continue to the adult stage. If the attack is too light for this, galleries are healed over and normal growth is gradually resumed. Such "unsuccessful attacks" may occur several times in a tree's history. The success of an attack depends on the vigour of the tree and the numbers of the insect.(c) Normally, the insect prefers mature or overmature trees or trees in which some other factor than age has seriously reduced the vigour of the part attacked. Given a large supply of such material to breed in, it is capable of increasing in numbers and as a result can successfully attack greater numbers of healthy trees.(d) The injury caused by the galleries may be due chiefly to the destruction of the phloem and the resulting interference with the conduction of food materials in an upward as well as downward direction.The following factors appear likely to have contributed to the present situation in New Brunswick: (1) The presence of large areas of mature and overmature stands; (2) The damage to birch from exposure following cutting for softwoods and dying of softwoods from budworm attack; (3) Repeated attacks by defoliators. There is no clear evidence of climatic factors having caused direct injury.Five classes of injury are suggested as a basis for sample plot tallies to estimate the need for salvage. The present increase in the numbers of the borer, however, demonstrates our failure to develop a sufficiently wide and stable demand for hardwood, coupled with good silvicultural management. Prevention of the injury depends on eliminating overmature stands and maintaining vigour of growth. Severe thinning or leaving birch on cut-over lands should be avoided.