THERMAL ACCUMULATIONS, DIAPAUSE, AND OVIPOSITION IN A CONIFER-INHABITING PREDATOR, CHRYSOPA HARRISII (NEUROPTERA)

1974 ◽  
Vol 106 (9) ◽  
pp. 969-978 ◽  
Author(s):  
Maurice J. Tauber ◽  
Catherine A. Tauber
Keyword(s):  
Diapause Induction ◽  
Temperature Threshold ◽  
Heat Accumulation ◽  
Species Occurrence ◽  
Winter Solstice ◽  
Critical Photoperiod ◽  
Diapause Development ◽  
Dark Green ◽  
Active Adults ◽  
Short Days

AbstractThe adults of Chrysopa harrisii Fitch, which are not predaceous, overwinter in a state of reproductive diapause. During both the dormant and the reproductive periods they remain dark green, a colour apparently adapted to the species’ occurrence on conifers. Two to three generations per season are possible in the Ithaca, N.Y., area.At 75°F, which is the optimum constant temperature for development and survival, the time from oviposition to adult eclosion is 29 days. Theoretical thresholds for development of all stages are relatively high, between 50° and 57°F, and development from egg to adult requires 566 heat degree days.In the laboratory, the critical photoperiod for diapause induction is between LD 13:11 and LD 14:10; short days maintain diapause for approximately 45 days (at 75°F); long days terminate diapause. Both newly-emerged and reproductively-active adults are extremely sensitive to diapause-inducing photoperiods. In the field, all adults emerging on 5 September or later enter diapause and it appears that diapause induction in the Ithaca population begins in the latter part of August. Short days maintain diapause until the end of December, and neither long days, increasing day lengths, nor low temperatures play a role in hastening diapause termination in nature.In timing its vernal reproduction, C. harrisii has evolved a strategy that combines an early-ending diapause with an apparently relatively high temperature threshold for post-diapause development. Therefore, although diapause ends around the winter solstice, heat accumulation is prevented until much later, when temperatures are relatively high.

EFFECT OF LATITUDE ON THE CRITICAL PHOTOPERIOD FOR DIAPAUSE INDUCTION IN THE BERTHA ARMYWORM, MAMESTRA CONFIGURATA (LEPIDOPTERA: NOCTUIDAE)

1983 ◽  
Vol 115 (8) ◽  
pp. 1039-1042 ◽  
Author(s):  
B. M. Hegdekar
Keyword(s):  
Temperature Regime ◽  
Diapause Induction ◽  
The Other ◽  
Fluctuating Temperature ◽  
Mamestra Configurata ◽  
Ambient Temperatures ◽  
Critical Photoperiod ◽  
Lepidoptera Noctuidae ◽  
H 20 ◽  
Bertha Armyworm

AbstractThe critical photoperiod for diapause induction in pupae of Mamestra configurata Walker in Manitoba was 16 h 06 min at Glenlea (49°38′ N), 16 h 20 min at Grandview (51°10′ N), and 16 h 42 min at Birch River (52°24′ N). The differences in cirtical photoperiods observed at Glenlea and Grandview were not significant. At least two different photoperiods exist, one in the Glenlea and Grandview areas and the other in the Birch River area. In the laboratory, the critical photoperiod was 13.5 h when larvae were exposed to a daily fluctuating temperature regime of 12 h at 25 °C and 12 h at 10 °C. Longer critical photoperiods found for the field populations may be related to the relatively low ambient temperatures to which the larvae were exposed in field cages.

scholarly journals Day-Length Control of Inflorescence Initiation in the Grass Rottboellia Exaltata L.F.

1962 ◽  
Vol 15 (2) ◽  
pp. 291 ◽  
Author(s):  
LT Evans
Keyword(s):  
Day Length ◽  
Inflorescence Development ◽  
Short Day ◽  
Critical Photoperiod ◽  
The One ◽  
Short Days

R. exaltata is a strict short�day plant with a critical photoperiod of about 13 hr. The number of short days required for inflorescence initiation varies with age, being 6 with plants 5 weeks old. Exposure to additional short days increases the rate of inflorescence development. The expanding leaf is the one most sensitive to short.day induction and removal of the leaves below it accelerates inflorescence development.

Diapause Induction in a Kentucky Population of Diprion similis (Hymenoptera: Diprionidae)

1999 ◽  
Vol 34 (3) ◽  
pp. 328-334 ◽  
Author(s):  
Heidi L. Melcher ◽  
Lee H. Townsend
Keyword(s):  
Diapause Induction ◽  
Pine Sawfly ◽  
Sensitive Stage ◽  
Diprion Similis ◽  
Critical Photoperiod ◽  
Photoperiod Sensitive ◽  
Chilling Period

Critical photoperiod, sensitive stage for diapause induction, and requirements for termination of diapause were studied in a colony of the introduced pine sawfly, Diprion similis (Hartig), established from a feral Kentucky population. We investigated induction of diapause in the laboratory under photoperiods of 10:14, 11:13, 12:12, 13:11, 14:10, 15:9, and 16:8 (L:D) in the first trial, and added a photoperiod of 9:15 (L:D) in the second trial. Individuals exposed to light periods ≤12:12 (L:D) entered diapause; individuals in a photoperiod > 13:11 (L:D) bypassed diapause. The sensitive stage was determined using reciprocal switches of diapause-inducing (9:15) and non-diapause inducing (16:8) L:D regimes. Our studies indicated that late instars of the introduced pine sawfly are significantly sensitive to photoperiod. Termination of diapause in D. similis did not require a cold or chilling period. All individuals from critical photoperiod trials were kept at 22°C to determine the duration of diapause. Diapausing individuals emerged from the cocoon after 82 to 105 d, compared to 6 to 23 d for individuals not entering diapause.

BIONOMICS OF THE DAMSEL BUG, NABIS AMERICOFERUS CARAYON (HEMIPTERA: NABIDAE), A PREDATOR OF THE ALFALFA BLOTCH LEAFMINER (DIPTERA: AGROMYZIDAE)

1986 ◽  
Vol 118 (8) ◽  
pp. 745-751 ◽  
Author(s):  
J.C. Guppy
Keyword(s):  
Second Generation ◽  
Acyrthosiphon Pisum ◽  
Developmental Rate ◽  
Temperature Threshold ◽  
Nymphal Stage ◽  
Two Generations ◽  
Highly Correlated ◽  
Diapause Development ◽  
Increasing Temperature ◽  
Alfalfa Blotch Leafminer

AbstractThe damsel bug, Nobis americoferus Carayon, develops through two generations a year in eastern Ontario. In early fall, females of the second generation develop a reproductive diapause but both sexes continue to feed until freeze-up. Post-diapause development begins in late March. Eggs are deposited singly in plant stems but several may be laid in close proximity. In alfalfa, most eggs were found where stem diameter measured from 0.8 to 1.9 mm but height of oviposition site was not related to length of stem. Females reared at 23°C laid an average of 157 eggs during a 3-week oviposition period. The immature stages of the first generation occurred from mid-April to mid-July and those of the second generation from mid-July to early September. The duration of each stage of N. americoferus, fed pea aphids, Acyrthosiphon pisum (Harr.), and held at four constant temperatures, 18, 23, 28, and 31°C, decreased with increasing temperature. There was a highly correlated linear relationship between rate of development and temperature for all stages. The theoretical temperature threshold for development of eggs was 11.1°C and that for the nymphal stage was 10.6°C; degree-day requirements for these stages were 123.5 and 370.4, respectively. Developmental rate of nymphs varied with host as well as temperature; nymphs fed larvae of the alfalfa blotch leafminer, Agromyza frontella (Rondani), developed significantly faster than those fed pea aphid.

scholarly journals Frost hardening in white cedar container seedlings exposed to intermittent short days and cold temperatures

1991 ◽  
Vol 67 (5) ◽  
pp. 542-544 ◽  
Author(s):  
S. J. Colombo ◽  
E. M. Raitanen
Keyword(s):  
Day Treatment ◽  
Frost Hardiness ◽  
Day Length ◽  
Cold Temperatures ◽  
Thuja Occidentalis ◽  
Frost Hardening ◽  
White Cedar ◽  
Container Seedlings ◽  
Dark Green ◽  
Short Days

Shoot frost hardiness development in white cedar (Thuja occidentalis L.) container seedlings in response to intermittent short days (4 days per week) and warm (not less than 15 °C) or cool (10/5 °C, day/night) temperatures was assessed using the diffusate-electrical conductivity technique. A slight increase in frost hardiness was found within 2 weeks of the start of warm, short days. Frost hardiness increased linearly with time under warm, short days from week 7 to week 14, with seedlings being resistant to damage at −10 °C on week 14. Approximately one-quarter of the seedlings developed brown-green foliage colour after 5 weeks of warm, short day treatment. These seedlings were significantly more frost hardy than the remainder of the seedlings which had dark green foliage. Seedlings exposed to warm, intermittent short days for 13 weeks and then to cool continuous short days for a further 6 weeks became hardy to −20 °C, while seedlings exposed to warm, intermittent short days only for the full 19 week period did not harden to the −20 °C level. Key words: Thuja, day length, photoperiod

Biology of tree-hole mosquitoes: photoperiodic control of development in northern Toxorhynchites rutilus (Coq.)

1975 ◽  
Vol 53 (7) ◽  
pp. 889-893 ◽  
Author(s):  
William E. Bradshaw ◽  
Christina M. Holzapfel
Keyword(s):  
Rapid Growth ◽  
Fourth Instar ◽  
Photoperiodic Control ◽  
The Third ◽  
Winter Conditions ◽  
Tree Hole ◽  
Critical Photoperiod ◽  
Northern Portion ◽  
Toxorhynchites Rutilus ◽  
Short Days

Carnivorous larvae of the tree-hole mosquito, Toxorhynchites rutilus, were collected from the northern portion of their range. Long days were found to promote rapid growth and metamorphosis from egg to adult; short days retard development during the second and third instars and evoke diapause in the fourth. All larvae exposed continuously to long days from embryos to the third or fourth instar developed without entering diapause. Diapause-averting long days experienced earlier in development could be reversed in at least some individuals by subsequent short days. Among laboratory-reared larvae or those caught early in the fall, the critical photoperiod for the maintenance of diapause is around 13 h of light per day. Among larvae caught in midwinter, diapause is not maintained in all larvae at any photoperiod and in 50% or less of the larvae at photophases shorter than 12.5 h. Winter conditions in the northern part of the range of T. rutilus appear to play a prominent role in the maintenance and termination of diapause.

Inhibitory effect of increased photoperiod on wool follicle growth

1996 ◽  
Vol 148 (1) ◽  
pp. 157-166 ◽  
Author(s):  
A J Pearson ◽  
A L Parry ◽  
M G Ashby ◽  
V J Choy ◽  
J E Wildermoth ◽  
...  
Keyword(s):  
Day Treatment ◽  
Inhibitory Effect ◽  
Plasma Prolactin ◽  
Follicle Growth ◽  
Primary Follicle ◽  
Winter Solstice ◽  
Natural Photoperiod ◽  
Wool Follicle ◽  
Plasma Prl ◽  
Short Days

Abstract The relationships between circulating prolactin (PRL), wool follicle growth and daylength were investigated in 24 New Zealand Wiltshire ewes housed indoors from September 1989 to May 1991. Twelve control (C) ewes were maintained under natural photoperiod. Two other groups were held in short days (SD; 8 h light:16 h darkness) commencing from the winter solstice (22 June 1990) for either three (group SD3, n=7) or six (group SD6, n=5) months before reversion to natural daylength. Skin was sampled at one- to four-week intervals for histological determination of percentages of growing primary and secondary follicles. Hourly blood samples over 24 h were collected via jugular cannulae from C sheep in March and July and then monthly from all animals until December 1990 for estimation of mean monthly PRL concentrations for each treatment group. Between autumn (March 1990) and winter (July) primary follicle activity (PFA) and secondary follicle activity (SFA) declined in C ewes (PFA: 97 to 43%, SFA: 100 to 57%). Follicle regrowth during July and August in eight C ewes preceded the initial rise in plasma PRL from the winter minimum (1·6 ng/ml). Across the three groups, four instances of decreased follicle activity were observed, closely following or concurrent with increases in plasma PRL concentrations. The resumption of spring growth in four C sheep was temporarily checked by falls in follicle activities during September and October as PRL concentrations began to increase (3·4 to 8·9 ng/ml). Follicle activity also declined in November and December in eight C sheep, coincident with the rapid rise in PRL to a seasonal maximum in late November (165·4 ng/ml). The increase in SD3 follicle activity over spring was not delayed by short days but during October, after release from treatment, PRL concentrations rose (1·8 to 12·0 ng/ml) and follicle activity declined (PFA: 65 to 38%, SFA: 68 to 43%). In SD6 ewes, PRL concentrations were suppressed (2·1 ng/ml) and relatively constant levels of follicle activity (PFA: 73%, SFA: 95%) were maintained throughout short-day treatment. Release of SD6 ewes into summer photoperiod in January 1991 temporarily interrupted follicle growth (PFA: 68 to 17%, SFA: 96 to 19%) and caused out-ofseason shedding in March and April. Contemporary C follicle activities were high (PFA: 95%, SFA: 98%). These data suggest that natural and experimental increases in daylength have a short-term inhibitory effect on growing wool follicles which could be mediated through rising concentrations of plasma prolactin. Journal of Endocrinology (1996) 148, 157–166

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