摘要:

The relationship between larval growth, body size, and the number of larval stages and fecundity ofQuadricalcarifera punctatella(Motschulsky) was investigated by rearing larvae under constant conditions. Fecundity, adult weight, and forewing area were strongly correlated. Forewing area measurement method may be good for estimating fecundity of field-trapped adults in future studies. Larvae were not able to develop at constant temperatures below 12°C, but the developmental threshold was estimated as ≍8.5°C for first and second instars. High temperatures>25°C also seemed to be unfavorable to larvae, because body size decreased and larval duration was prolonged. Larval development was comprised of four or occasionally five instars. This extra molt lengthened the duration of the larval stage and enlarged body size. Because larger mature larvae became larger adults with greater fecundity, larval growth was important in determining fecundity. There was a tendency for larvae exhibiting five instars to be smaller during the third stadium. There was also an increased frequency of extra instars at high temperatures. This phenomenon can be explained by a cost-benefit trade-off; prolongation of the larval period caused by an extra molt may result in increased mortality (a cost), but i also causes increased body size and fecundity (a benefit). And, the larval period of individuals with four instars was longer at 25°C than at 20°C, but no such developmental delay was observed for larvae with five instars. An extra molt is, therefore, also an adaptation to high temperatures. These trade-offs could also explain the variation in numbers of instars among years in field populations; extra instars were less common in 1982 when larval duration was longer than in the other 2 yr, especially at low temperatures.

DOI:10.1093/ee/24.3.648

出版商:Oxford University Press    

年代:1995

数据来源: OUP

摘要:

Eurosta solidaginis(Fitch) infesting the host plantSolidago giganteaAit form larger galls than individuals attacking the presumed ancestral host,S. altissimaL. Because previous studies found thatEurytoma giganteaWalsh parasitism is restricted to smaller galls, it was hypothesized that this gall-size difference could result in decreased parasitism ofE. solidaginisinfestingS. gigantea. E. solidaginisgalls were collected along a transect from Pennsylvania to Minnesota and from two sites in Iowa to determineE. solidaginissurvivorship and causes of mortality. AlthoughS. giganteagalls were generally larger thanS. altissimagalls, there was no significant decrease inE. giganteaparasitism forE. solidaginisoccupyingS. giganteagalls. Galls containing the parasitoidE. giganteawere significantly larger on the host plantS. giganteathan onS. altissima. Parasitoid access toE. solidaginiswas not limited by the larger size ofS. gigallteagalls.Eurytoma obtusiventrisGahan parasitism was restricted to galls onS. altissimaand this parasitoid occurred only in the more eastern parts of our transect. Differences in gallmaker survivorship and natural enemy occurrence betweenSolidagohosts at sympatric sites were dependent on site; predation by the beetleMordellistena unicolorLec. was the primmy determinant of differences in gallmaker survivorship betweenSolidagohosts and among geographic sites.

DOI:10.1093/ee/24.3.657

出版商:Oxford University Press    

年代:1995

数据来源: OUP

摘要:

The effect that harsh, variable desert temperatures might have on the structure and population dynamics of a guild of Bruchidae (Coleoptera) that feed in the seeds of mesquite,Prosopis velutinaWooten, was examined in a 3-yr field and laboratory study. Metabolic rate, fecundity, longevity, developmental times, survivorship, and body size were measured across the temperature spectrum in which the species normally live. The 4 species that compose the guild—Algarobius prosopis(LeConte),Mimosestes amicus(Hom),Mimosestes protractus(Hom), andNeltumius arizonensis(Schaeffer)—divide the use of the resource temporally. The first 2 species dominate resource use and overlap entirely in time, whereas the 2 latter minor species utilize opposite ends of the temporal resource spectrum. Of the two dominants,M. amicusfunctions as a physiological generalist, apparently sacrificing resource adaptation for greater temperature adaptation and very high reproductive output. In contrast,A. prosopisiswell adapted to both the use of mesquite as a resource and also to the desert thermal environment. The 2 minor species seem to be less well adapted to both the resource and the environment. Temperature clearly plays a strong role in determining the structure of this guild of bruchids.

DOI:10.1093/ee/24.3.663

出版商:Oxford University Press    

年代:1995

数据来源: OUP

摘要:

The relationship between caste polymorphism and foraging strategy was examined in the Florida harvester ant,Pogonomyrmex badius(Latreille). Foragers ofP. badiuswere offered two sizes of barley seed (4 or 33 mg) at 1, 2, 5, and 10 m from the nest entrance. No consistently significant correlations were found between forager size and the size of seed collected. Distance of seed from the nest was not associated with worker size or seed selection. In this species, it does not appear that polymorphism can be explained by simple models of foraging optimization through the pairing of worker size and seed size.

DOI:10.1093/ee/24.3.673

出版商:Oxford University Press    

年代:1995

数据来源: OUP

摘要:

The cecidomyiid midge,Rhopalomyia californicaFelt, forms galls on the perennial evergreen shrubBaccharis pilularisDe Candolle, which is found in coastal regions throughout central California.R. californica, however, is not found in the more southern part of its host's range and is essentially absent south of Santa Barabara. Reasons for this restricted distribution were examined by field experiments at 2 sites: Santa Barbara and Big Creek, which is located 290 km to the North, well within the area where galls are widespread and abundant. No differences in plant suitability for oviposition were detected between the 2 sites when the midges were protected from predators, but midges responded differently to the plants, each midge producing more galls at Santa Barbara but each gall containing, on average, fewer larval chambers. Mortality caused by predators (or other sources of egg or early-larval mortality) was significantly higher at Santa Barbara than at Big Creek, reducing both the number of galls produced per female and also the average number of chambers per gall that was produced. Mortality caused by parasitoids was also significantly higher at Santa Barbara than at Big Creek. There was no evidence for spatial density dependence at either site. When combined with realistic parasitism rates and likely fecundities, such mortality rates result in a negative growth rate over the period studied for galls at Santa Barbara but a positive growth rate at Big Creek, providing a possible reason for the restricted distribution of the midge.

DOI:10.1093/ee/24.3.679

出版商:Oxford University Press    

年代:1995

数据来源: OUP

摘要:

A model was developed to estimate the effect of predation byEpisyrphus balteatuslarvae on aphid populations in fields of winter wheat. Feeding rate of syrphid larvae was estimated from experiments in field cages using a Holling type-III function. During larval development, syrphids consumed a maximum of 396 aphids, which is only half the potential feeding rate reported from laboratory experiments. The lower consumption rate in the field may be attributed to the additional time required by the predators to find prey. Isoclines derived from the model were used to estimate the abundance of syrphid larvae necessary to prevent further pest increases.

DOI:10.1093/ee/24.3.687

出版商:Oxford University Press    

年代:1995

数据来源: OUP

摘要:

Verbenone significantly reduced catches ofIps latidens(LeConte),I. pini(Say), andDendroctonus ponderosaeHopkins in multiple-funnel traps, baited with aggregation pheromones, in stands of lodgepole pine in southern British Columbia. Interruption of attraction was dose dependent for all three species. There were no significant differences in attraction between the sexes. Variation in successful use of verbenone in protecting pine stands partially may be explained by the dose-dependent variation in responses.

DOI:10.1093/ee/24.3.692

出版商:Oxford University Press    

年代:1995

数据来源: OUP

摘要:

Populations ofEurosta solidaginisFitch andEpiblema scudderiana(Clemens) attacking ramets ofSolidago altissimaL. were sampled in 1991 and 1992 on road margins (10 and 60 m from the road edge)in the Ottawa metropolitan area to investigate the effects of roadside conditions on the performance of gall-forming insects and their host plants. The growth ofS. altissimawas reduced near the road throughout the growing season in 1992 and similar trends were observed in 1991. However, the biomass of gall-inhabiting larvae and gall size did not differ significantly or consistently between the two distances from the road edge. Similarly, larval survivorship and mortality agents of gall-formers and the proportion of goldenrod ramets attacked byE. solidaginisandE. scudderianawere unaffected by roadside conditions. Thus, road stress may affect the host plant, but it is probably not severe enough to affect gall-formers, which might be better adapted to harsh environments and better protected against stress-induced changes in the quality of their food plant, as opposed to other guilds of insect herbivores such as sucking insects.

DOI:10.1093/ee/24.3.697

出版商:Oxford University Press    

年代:1995

数据来源: OUP

摘要:

We studied populations of the willow feeding leaf beetle,Melasoma lapponicaL., m the vicinity of the Severonikel smelter complex at the Kola Peninsula, northwest Russia. Increased abundance ofM. lapponicaaround the smelter is explained by habitat changes that have resulted in higher density of the most preferred host plant,Salix borealis(Fries) Nasar. Within the polluted territory, 10- to 20-fold higher densities occurred in moderately polluted sites than both in heavily and slightly polluted areas. Laboratory experiments demonstrated the highest survival of insects fed with leaves ofS. borealisfrom the moderately polluted site, whereas female life span, fecundity, and egg viability decreased towards the smelter. Host-plant quality together With parasite-induced mortality explained the density pattern observed along pollution gradients.

DOI:10.1093/ee/24.3.707

出版商:Oxford University Press    

年代:1995

数据来源: OUP

摘要:

To establish an efficient method for preservation of field-collected beetles for molecular genetic analyses, 5 different preservation treatments were compared: ethyl acetate,ethanol, Camoy fixative, DNA isolation buffer, and liquid nitrogen. Cryopreservation by immersion in liquid nitrogen and subsequent storage at −80°C was found to be the best method for long-term storage. Storage in ethanol at room temperature preserved the DNA for ≍6 wk. Storage in DNA isolation buffer was also effective but required the insects to be thoroughly homogenized to produce intact DNA, which destroyed insect morphology. Ethyl acetate and Camoy fixative did not preserve the DNA. Preservation in ethanol was the easiest method, because it neither required grinding of insects nor transportation and maintenance of special equipment, such as a dewar flask for liquid nitrogen. However, because the DNA was found to degrade after ≍6 wk, ethanol was useful only for short-term storage.

DOI:10.1093/ee/24.3.716

出版商:Oxford University Press    

年代:1995

数据来源: OUP