摘要:

The effects of spatial differences in host density on parasitism ofHeliothis zea(Boddie) eggs byTrichogrammaspp. were investigated in cultivated soybean plots.H. zeaegg density per leaf and the distance separating egg-bearing leaves within lots were experimentally manipulated. A kairomone-containing extract ofH. zeascales was used to mimic natural oviposition sites. Spatial relationships between the probability of parasitism and egg density per leaf were the result of 2 opposing trends. The probability of at least one egg on an eggbearing leaf being encountered and parasitized byTrichogramma(here termed a “discovery” of that leaf by parasitoids) increased as the egg density per leaf increased; the conditional probability of parasitism for other eggs present, given an attack on one egg, decreased with increasing egg density. The net result of these opposing trends varied with separation distance and, statistically, percent parasitism varied from inversely density-dependent to density-independent as separation distance increased from 25 to 150 cm.

ISSN:0046-225X    

DOI:10.1093/ee/9.1.79

出版商:Oxford University Press    

年代:1980

数据来源: OUP

摘要:

NorthernWyeomyia smithii(Coquillett) (Diptera: Culicidae) are obligatorily autogenous; southernW. smithii, although capable of autogenous development, may consume a blood meal. The clutch of eggs resulting from a blood meal contributes little to capacity for increase. Capacity for increase is inversely correlated with mean crowding of the overwintering population. These results suggest that the principal role of hematophagy inW. smithiirelates to increasing the contribution to total reproductive effort made by the 2nd and subsequent ovarian cycles.

ISSN:0046-225X    

DOI:10.1093/ee/9.1.86

出版商:Oxford University Press    

年代:1980

数据来源: OUP

摘要:

Acyrthosiphon kondoiShinji did not produce sexual forms when reared under controlled conditions of 15 combinations of temperature and photoperiod. Apterae were predominantly produced at higher temperatures (20° and 25° C) at all photoperiods (8-, 12-, and 16-h photophase/24 h) except at 25° C/8-h photophase when alatae were produced. Low temperatures (10° and 15° C) generally caused alatae to be produced except at 15° C/8-h photophase when apterae were predominantly produced. The aphid switched from the production of one alary morph early in the reproductive period to the production of the opposite morph later in the reproductive period at all temperature/photoperiod regimes except 20°/16 h when no switching occured. The cause of form switching was not attributable to temperature or photoperiod, but is believed to be an inherent biological phenemenon associated with survival mechanisms.

ISSN:0046-225X    

DOI:10.1093/ee/9.1.94

出版商:Oxford University Press    

年代:1980

数据来源: OUP

摘要:

Relative abundance and seasonal occurrence of hymenopterous parasites of the southern pine beetle (Dendroctonus frontalisZimm.) were studied in loblolly pine (Pinus taedaL.) stands located in southeastern and western Louisiana. The 6 most abundant parasites were:Roptrocerus eccoptogastri(Ratz.)–65% of total complex,Coeloides pissodis(Ash.)–10%,Dendrosoter sulcatusMues.–8%,Spathius pallidusAsh.–7%,Heydenia unica(Cook and Davis)–7%, andDinotiscus(=Cecidostiba)dendroctoni(Ash.)–3%. Parasite abundance peaked between Apr.-June and remained at low levels from Dec. to Mar. Parasite populations within trees differed little between areas of opposing site conditions and geographic location.The relationship between host and parasite populations and bark thickness of loblolly pine, host egg gallery length (number of beetle eggs) and site differences at 2 ecologically different areas were also investigated. Bark thickness significantly affected populations of the parasitic species that oviposit through the bark but did not influence populations ofR. eccoptogastriwhich enter host galleries and oviposit through host egg niche plugs.

ISSN:0046-225X    

DOI:10.1093/ee/9.1.97

出版商:Oxford University Press    

年代:1980

数据来源: OUP

摘要:

The durations of the egg, pupal, and larval stages of the pickleworm,Diaphania nitidalis(Stoll), were determined at 8 temperatures. Survival at all stages declined at temperatures>29.4°C. Pickleworm pupae were sensitive to cold; LD 50's at 4.4°, −1.0°, and −6.7°C were 134.9, 6.0, and 1.3 h, respectively. Mean fecundity ranged from 300 – 400 eggs at 26.7° and 21.1° to only 83.2 eggs at 32.2°C.

ISSN:0046-225X    

DOI:10.1093/ee/9.1.101

出版商:Oxford University Press    

年代:1980

数据来源: OUP

摘要:

Honey bees,Apis melliferaL., from 5 colonies, were placed in laboratory cages supplied with either 46.75 or 140.25 cm2of comb surface area (CSA) that was either dark-brown brood comb or light-yellow comb.A 3-way analysis of variance showed that bees hoarded more in the presence of greater CSA (P<0.005). Overall, bees did not hoard more in the presence of either color of comb. Bees from different colonies hoarded at different rates (P<0.005). Hoarding responses for bees from different colonies interacted with responses to different colors of comb (P<0.025). This interaction opens the possibility for the genetic selection of stock that would produce maximum amounts of honey when supplied with light storage combs.

ISSN:0046-225X    

DOI:10.1093/ee/9.1.104

出版商:Oxford University Press    

年代:1980

数据来源: OUP

摘要:

Multivariate data obtained at triweekly intervals for 60 wk from 8 insect-infested wheat bulks, 157 kg each maintained at 30°±2°C, was interpreted with canonical correlation analysis. One system consisting of 2 bulks of insect-free wheat served as a control; a 2nd system of 3 bulks was artificially infested withRhyzopertha dominica(F.),Sitophilus oryzae(L.), andTribolium castaneum(Herbst) (RST); and a 3rd system of 3 bulks was infested withCryptolestes ferrugineus(Stephens),Oryzaephilus surinamensis(L.), andTribolium castaneum(COT). Low populations of a mite,Tarsonemus granariusLindquist were naturally present in all bulks. Canonical correlation analysis of abiotic and biotic variables identified and quantified interrelations within the systems. The canonical correlation of the first set of canonical variables ranged from 0.906–0.936 in the 3 systems. The 1st 3–4 pairs of canonical variables were significant (P<0.01) in all of the systems; for the control system, the 1st pair of canonical variables revealed that the fungusAlternaria alternata(Fr.) Keissler and bacteria were closely related to fat acidity values (FAV) of the wheat, seed germination, dust weight and O2levels. In the RST system,Alternaria, bacteria, andSitophiluswere related to FAV, CO2levels, grain moisture, germ and endosperm damage, and seed germination. In the COT systemAlternaria, bacteria,TriboliumandCryptolesteswere related to the variables FAV, CO2, dust weight, germ damage and seed germination.

ISSN:0046-225X    

DOI:10.1093/ee/9.1.106

出版商:Oxford University Press    

年代:1980

数据来源: OUP

摘要:

Spatial dispersion patterns of flying southern pine beetles,Dendroctonus frontalisZimm., and the clerid predatorThanasimus dubius(F.) were determined within 3 natural infestations of southern pine beetle (SPB) in eastern Texas using grids of sticky traps. There was significant positive association of the 2 insects throughout the trapping grids, although aerial population densities of the clerid were inversely related to aerial densities of SPB.Aggregation patterns were quantified using the index of patchiness (IP) and the regressions of mean crowding (M*) on mean density (m). Both methods showed a highly clumped pattern for both beetle species. SPB density in the infestations was positively associated with the daily rate of tree attack by the beetles, but the degree of population aggregation in the infestations was inversely related to the daily rate of tree attack. Although densities of the two species did not follow the same trends among the 3 infestations, the degree of aggregation did (i.e., SPB was most highly aggregated in the location whereT. dubiuswas most highly aggregated) and Lloyd's index of interspecific patchiness indicated overlapping aggregate distributions.A kairomonal response mechanism forT. dubius, and SPB co-aggregation within infestations is hypothesized.

ISSN:0046-225X    

DOI:10.1093/ee/9.1.113

出版商:Oxford University Press    

年代:1980

数据来源: OUP

摘要:

MaleHeliothis virescens(Lepidoptera: Noctuidae) were shown to transfer 36% of a whole body65Zn burden to the females at the time of mating. Approximately 5% of the male's and 11% of the female's total65Zn burdens were found in eggs oviposited during a 10-day period following mating. Transfer of zinc at mating byHeliothismales may represent the conservation of an essential trace element that must be retained throughout the life cycle.

ISSN:0046-225X    

DOI:10.1093/ee/9.1.119

出版商:Oxford University Press    

年代:1980

数据来源: OUP

摘要:

Over the past 30 yr the western corn rootworm (WCR)Diabrotica virgiferaLeConte, largely displaced the northern corn rootworm (NCR),D. longicornis(Say), as the dominant rootworm species in eastern Nebraska. Only in the northeast cropping district has the NCR exhibited significant persistency. Here a comparative study of the ecology and behavior of the 2 species disclosed specific distributional and behavioral differences. The avg no. and percentage of the 2 species varied according to whether the samples were from “upland” or “lowland” fields. The NCR was significantly more abundant in upland fields. The NCR dispersed more readily from cornfields to weedy oat stubble and soybean fields, whereas the WCR for the most part moved from corn to other cornfields. These behavioral differences, coupled with prevailing farming practices (continuous corn vs corn in short rotations), partially explain the displacement phenomenon and varying degrees of coexistence now observed between the NCR and WCR in different areas of Nebraska. The southern corn rootworm (SCR),D. undecimpunctata howardiBarber is of minor importance as a pest of corn in Nebraska.

ISSN:0046-225X    

DOI:10.1093/ee/9.1.122

出版商:Oxford University Press    

年代:1980

数据来源: OUP