Printer Friendly

Thermal time clock for estimating phenological development of Schistocerca piceifrons piceifrons Walker (Orthoptera: Acrididae) in northeastern Mexico.

Introduction

The Central American locust, Schistocerca piceifrons piceifrons Walker, is an economically important agricultural pest in Mexico and Central America, affecting almost all crops. Heavy infestations of this pest have occurred since early in 1998, causing severe damage to a diversity of annual and perennial plants in the Huasteca region (South Tamaulipas, East San Luis Potosi, North Veracruz and the State of Hidalgo) (DCSV 2003, Barrientos-Lozano et al. 2004). Biology, ecology and integrated management of S. p. piceifrons have been the subject of numerous studies (Barrientos-Lozano 2001 a, b, c, d; Barrientos-Lozano 2005; Barrientos-Lozano et al. 2004; Poot 2005; Avila-Valdez et al. 2005; Avila-Valdez et al. 200 G). These works have been crucial in understanding the behavior and the interaction of this insect in the ecosystem.

The species has two generations per year: the first generation occurs from May to August-September (60-80 d) and the second from October-November to May (155-180 d). Second generation, sexually immature adults go through a diapause period from December to April; diapause ends in Spring (March-April) and with the onset of the rainy season adults become sexually mature and begin mating (Barrientos-Lozano 2001b, c).

As poikilotherms, all insects adopt the temperature of the environment and therefore their rates of development are directly related to the airtemperature within a particular interval ([k.sub.1], [k.sub.2]). In contrast to homeotherms, whose rate of development is conveniently expressed as a function of Julian or calendar time ([day.sup.-1]), in poikilotherms, this is not so, unless the temperature remains constant during the whole developmental cycle. Instead, the rate of development of poikilotherms is best expressed as a function of thermal time, whose units are degree-days [[[degrees]C-days].sup.-1] (Higley et al. 1986). For insect species which enter a diapause period, as is the case of the Central American locust, besides air temperature the day length may also play an important role in regulatory mechanisms. An insect's phenology models, expressed as a function of thermal time, may be useful in predicting pest development dates, monitoring scheduling, risk assessment analysis, predicting migration tracks and planning control actions (Mellors & Bassow 1983, Kauffman et al. 1985, Pinto et al. 2002). Online data bases are available to support insect model designs, for example, temperature thresholds and thermal times for insect development of many crop pests economically important: e.g., (UC-IPM Online): (1) www.ipm.ucdavis.edu/_WEATHER/ ddconcepts.html), (2) www.nappfast.org/pdf/IDD%202007.pdf.

Temperature and light are the most important single nonbiotic factors associated with the rate of growth and development of the Central American locust; however, other climatic variables also play significant roles. For example, early rain promotes copulation as well as egg laying, whereas a high relative humidity protects eggs and immature stages from dehydrating, and by so doing improves locust fertility and survival rates. High relative humidity may also increase locust susceptibility to the attack of naturally occurring entomopathogenic fungi, which might result in a decrease in locust population growth. Locust food availability (plant growth) is positively related with rain frequency and total precipitation. Finally, temperature gradients, solar radiation and light intensity may also play a role in migration, inasmuch as locusts show positive thermo-and phototropic effects (Porter et al. 1991; Cornford 1991 cited by Retana 2003; Barrientos-Lozano 2001a, b). While studying the effects of temperature on locust swarm migration, Uvarov (1935) reported two types of responses: a) an increase in swarm excitability when in contact with a warm soil surface and b) an increase in reflex actions, as expressed in terms of an increased jump length of individuals belonging to young swarms. More recent work (Retana 2003), establishes the relationship between sea surface temperatures "El Nino Southern Oscillation (ENSO), and the potential of this pest.

The aim of this study was to design an easy-to-use model, a Thermal Time Locust Development Clock (TTLDC), of help to biologists, entomologists and agronomists making decisions in locust management, such as predicting pest development dates, monitoring scheduling, making risk assessment analyses, predicting migration tracks and planning control actions.

Materials and methods

The work was conducted in southern Tamaulipas, Mexico, in an area between parallels 22[degrees]00'00" and 23[degrees]15'00" north latitude and meridians 98[degrees]00'00" and 100[degrees]00'00 west longitude, at elevations from 0 to 380m a.s.l., from the coastal plain of the Gulf of Mexico, to the foothills of the Sierra Madre Oriental (SMO). Climatic conditions are defined by latitude, elevation and proximity to the Gulf of Mexico. The Tropic of Cancer divides the state into two climatic zones--the south with warm, humid climate and the north, less warm, with its little rain distributed throughout the year (INEGI 1983).

The grand mean monthly thermal time of the study area was calculated from the mean monthly minimum and mean monthly maximum temperatures of each of 20 meteorological stations (Table 1). Thermal time ([degrees]C-days) was calculated by the Allen sine method (1976), locating the axis of coordinates at the point (O,[T.sub.med]). Thermal thresholds for the Central American locust, k1 and k2, were taken from Barrientos-Lozano et al. (2004). Comparing temperature thermograms [T.sub.max] and [T.sub.min] < [k.sub.1] with [k.sub.1] and [k.sub.2] there were six possible cases, but only three of them occurred in the area. This meant it required only three different equations for calculating thermal time: case 1, all thermogram temperatures are within the interval [k.sub.1][less than or equal to]T[less than or equal to][k.sub.2](Fig. 1a); case 2, the daily minimum temperature is less than the lower threshold ([T.sub.min] < [k.sub.1]) and the maximum is located within the threshold values ([k.sub.1] [less than or equal to][T.sub.max][less than or equal to][k.sub.2]) (Fig. 1b); this condition occurs frequently during the winter months, when locusts are in diapause; case 3, the thermogram maximum daily temperature is greater than the upper threshold ([T.sub.max]> [k.sub.2]) and the minimum is located within the interval [[k.sub.1][less than or equal to][T.sub.min][less than or equal to][k.sub.2]] (Fig. 1c); this usually occurs during spring and summer months (April-August). Cases 4, 5 and 6 are theoretically possible, but not probable in the area under study: [case 4 ([T.sub.min]< [k.sub.1]) and ([T.sub.max] > [k.sub.2]), case 5 ([T.sub.max] [greater than or equal to] [k.sub.2]), case 6 ([T.sub.max] [less than or equal to] [k.sub.1])].

Day length (photoperiod), was obtained from latitude values given in Tables 1 and 2, which present monthly average day-length values (hours) for different latitudes (Mexican National Meteorological Service). For latitude values not listed in Table 2, linear extrapolation was used.

To calculate the daily number of hours at which the air temperature is less than 15.3[degees]C, diapause cool hours (case 2, Fig. 1b), the thermogram was adjusted by the method of Rodriguez-Absi et al. (2007) and Rodriguez-Absi (1997), using two functions: a sine function for the photoperiod and a decreasing exponential function for the night portion, as shown in Figure 2. It is convenient to separately analyze each part of the thermogram for establishing the equations which are needed in each case (Fig. 3).

Microsoft[R] Office Excel 2003 (Microsoft Corp., 2003) was used for: a) calculating daily thermal time using the derived equations for the three cases (1a,b,c) already discussed; b) calculating the day length (photoperiod) by linear extrapolation; c) calculating the number of hours below 15.3[degrees]C which occur during diapause, using the derived cooling hours equations of Figure 3.

Input data included mean monthly minimum and mean monthly maximum temperatures of the 20 meteorological stations listed in Table 1, latitude values and temperature threshold values ([k.sub.1] and [k.sub.2]). The program also calculated the monthly angular contribution to the clock and also the relationship between thermal time and a clock's angle. Thus, the following equations were also incorporated into the Excel program:

a) average monthly thermal time:

[PSI]monthly = [PSI]mean daily * (days/month)

b) average yearly thermal time:

[MATHEMATICAL EXPRESSION NOT REPRODUCIBLE IN ASCII]

c) average angular monthly contribution to the thermal clock:

[alpha][month.sub.i] = [PSI][month.sub.i]/[PSI]yearly x 360

d) relationship between thermal time and a clock's angle:

[PSI] = [PSI]yearly/360[degrees] [alpha]

Once those calculations were performed and the clock was drawn, average locust phenological development data and other relevant information were incorporated into the clock, including dates at which developmental stages do occur, diapause period, etc., (Barrientos-Lozano 2001 a,b,c,d; Barrientos-Lozano 2005; Barrientos-Lozano et al. 2004; Avila-Valdez et al. 2005; Avila-Valdez et al. 2000).

Results and Discussion

The calculated yearly thermal time ([[PSI].sub.yearly]) and Diapause Cool Hours (DCH) for the 20 meteorological stations are shown in Table 2. Maximum ([[PSI].sub.yearly]) thermal time variation between the two more discrepant stations (Table 2) was 29%, (i.e., 4272.3/3311.2-1 * 100), while DCH hours variation was about 25% (i. e., 2065/ 1655-1 * 100). However, a better estimate of variability is obtained by dividing the values by the average value of the group, e.g., when ([[PSI].sub.yearly]) thermal time largest and smallest values are compared with the grand mean, the variability drops to 12.5 and 14.7% respectively. Analogous calculations for DCH result in a variation of 8 and 15.G% for extreme values, when such values are compared to the grand mean.

A TTLDC for south Tamaulipas, Mexico is shown in Figure 4. Note that in contrast to a regular calendar time clock in which all month angles would be approximately equal (30[degrees]), the monthly angles in a TTLDC may be quite different; for example, May's angle is 50[degrees], whereas December's is only 16[degrees]. This means that May offers more than three times as many degree days for locust development as does December, i. e., locust development rate in May is more than three times faster than that in December.

The relationship between ([[PSI].sub.yearly]) thermal time ([degrees]C-days) and the angular values [alpha] is [PSI] = 10.6 [alpha], as expressed in the center of the clock (Fig. 4). This means that a unit angle in the clock = 10.6 [degrees]C-days of thermal time. For example, an egg laid on 25th April, may hatch on May 15th (first instar nymph); the angle comprised between these two dates is ~30[degrees], resulting in [PSI] = 10.6*30 = 318 [degrees]C-days, as shown in Fig. 4. The thermal time involved in transition from one stage to another is calculated in an analogous manner, i. e., by multiplying the constant 10. G by the angle which comprises the change of stage.

The period from November to April is particularly interesting. This is when second generation adult locusts are in diapause. During this period not only do the lowest temperatures of the year occur, but also the photoperiod shortens. The average monthly number of cold days and the average monthly photoperiod for October to April are shown in Fig. 5. It is suggested that the input signal to initiate diapause is controlled by day length (Fp), particularly when Fp [less than or equal to] 11h: this occurs November 18th to 30th; the number of cooling hours is increasing at an approximate rate of 288 hours per month as shown in Figure 5.

[FIGURE 1a OMITTED]

[FIGURE 1b OMITTED]

[FIGURE 1c OMITTED]

The diapause stage continues whenever the rate of cooling is greater than 288 hours [month.sup.-1] (12 to 13 cold-days/month; T [less than or equal to] 15.3[degrees]C/month) and concludes when Fp12h. The average total number of cooling hours, which occurs during the whole diapause interval, is around 1914 (Table 2).

Immature individuals of the Central American locust, similar to other locust migratory species, show phenotypic plasticity; this is defined as the capacity of a given genotype to produce different phenotypes in response to varying environmental conditions (Pigliucci 2001). For example, diapause entrance of S. p. piceifrons occurs with last instar, green-color nymphs. These individuals are solitary and avoid encounters with other individuals. As the number of solitary nymphs increases, they develop pink to red color with intense black pigments and become gregarious (Fig. 6).

Changes occur not only in color but also in behavior; a density-dependent gregarious mechanism is activated and may result in swarms of millions of individuals. The dorsal black stripes allow the insect to be more efficient at absorbing solar radiation, raising its body temperature and metabolic activity; this is important during the winter (diapause stage) because temperature may drop several degrees below [k.sub.1] (15.3[degrees]C).

To incorporate Locust Development Stages, Diapause Cooling Hours and Day length data into the TTLDC, three circles were added (Fig. 7); the outermost circle comprises life history stages of the Central American locust. This circle moves in phase with the 10[degrees]-angle graduated circle. The inner two circles correspond to photoperiod (day length) and cold hours, respectively. For example, when the zero of the angular section (10[degrees] degrees graduated circle) is set at the date when last instar nymphs are initially observed (i.e., Nov 15th) (Bio-fix point), the average dates at which other stages of development occur, may be read on the scale dates: since the angle remains constant (it is proportional to thermal time), variation is only in dates. Data on life history, ecology and field observations from 2001 to 2008 on the Central American locust (Barrientos-Lozano 2001a, b, c; Barrientos-Lozano 2005; Barrientos-Lozano et al. 2004; Avila-Valdez et al. 2005; Avila-Valdez et al. 200 G) are consistent with the development time estimated in the average TTLDC. Variation is due to fluctuations of temperature and moisture typical of different years, so the life cycle of this pest is advanced or delayed.

[FIGURE 2 OMITTED]

Conclusions

This average Thermal Time Locust Development Clock (TTLDC), obtained for the Central American locust, can be used to predict timing of phenological stages of this pest; this implies a starting date (Bio-fix). This date is experimentally established after obtaining quality data on population dynamics and on the life cycle of the pest. Reliability of predictions depends upon accuracy of the starting date and deviations in weather condition from the average year. When the TTLDC was compared with field observations, the differences were relatively small.

Building a TTLDC involved calculations using average values: temperature, day length, diapause cool hours and calendar dates. Thus it may be expected that the clock provides reasonably good estimates for predicting locust phenological development in south Tamaulipas, Mexico. However, more accurate clocks may be built, incorporating other variables such as relative humidity, rain etc. More specific clocks could be developed for smaller areas and used in local pest management programs. At present, several minimeteorological stations connected to the web have been installed throughout. This may facilitate analysis on pests' life cycle vs climate data using the methods already discussed.

[FIGURE 3 OMITTED]

[FIGURE 4 OMITTED]

[FIGURE 5 OMITTED]

[FIGURE 6 OMITTED]

[FIGURE 7 OMITTED]

Acknowledgments

Special thanks to the Mexican Council for Science and Technology (Fondo Mixto de Fomento a la Investigacion Cientifica y Tecnologica, CONACYT-Cobierno del Estado de Tamaulipas), for funding the research Project "Desarrollo de un proceso tecnologico para el control biologico de la langosta centroamericana (Schistocerca piceifrons piceifrons Walker) y acridoideos plaga en la region sur de Tamaulipas". Clave Tamps-2005-C08-26. We acknowledge the facilities provided by the Instituto Tecnologico de Cd. Victoria, and assistance and support during fieldwork provided by Pablo Garcia-Salazar, Junta Local de Sanidad Vegetal, Mante-Comite Estatal de Sanidad Vegetal Tamaulipas. The assistance provided by Jonathan Michel Alvarez-Garcia for editing figures and tables is greatly appreciated.

Accepted March 15, 2009

References

Avila-Valdez J., Barrientos-Lozano L., Garcia-Salazar P. 2005. Biologia y comportamiento de la langosta centroamericana (Schistocerca piceifrons piceifrons Walker) en el sur de Tamaulipas, pp. 31-35. In: Barrientos-Lozano L., Almaguer-Sierra P. (Eds) Memoria 2do. Curso Internacional: Manejo Integrado de la Langosta Centroamericana (Schistocerca piceifrons piceifrons Walker) y Acridoideos plaga en America Latina. Cd. Victoria, Tamaulipas, Mexico.

Avila-Valdez J., Barrientos-Lozano L., Garcia-Salazar P. 2006. Manejo Integrado de la langosta centroamericana (Schistocerca piceifrons piceifrons Walker) (Orthoptera: Acrididae) en el sur de Tamaulipas. Entomologia Mexicana 5: 636-641.

Barrientos-Lozano L. 2001 a. El problema de la langosta (Schistocerca piceifrons piceifrons Walker) en Mexico y Centro America, pp. 1-11. In: BarrientosLozano L. (Ed.) Memoria Curso I Internacional. Ecologia, Manejo y control de la Langosta Voladora (Schistocerca piceifrons piceifrons Walker). Altamira, Tamaulipas, Mexico.

Barrientos-Lozano L. 2001b. Prospeccion, monitoreo, vigilancia, densidad de poblacion y umbral economico de la langosta Centroamericana, pp. 66-79. In: Barrientos-Lozano L. (Ed.). Memoria Curso I Internacional. Ecologia, Manejo y control de la Langosta Voladora (Schistocerca piceifrons piceifrons Walker). Altamira, Tamaulipas, Mexico.

Barrientos-Lozano L. 2001c. Dinamica poblacional, biologia, ecologia y comportamiento de la langosta voladora (Schistocerca piceifrons piceifrons Walker), pp. 43-52. In: Barrientos-Lozano L. (Ed.) Memoria Curso I Internacional. Ecologia, Manejo y control de la Langosta Voladora (Schistocerca piceifrons piceifrons Walker). Altamira, Tamaulipas, Mexico.

Barrientos-Lozano L. 2001d. Comportamiento gregario y causas de gregarizacion (teoria de fases), pp. 55-G5. In: Barrientos-Lozano L. (Ed.) Memoria Curso I Internacional. Ecologia, manejo y control de la langosta voladora (Schistocerca piceifrons piceifrons Walker). Altamira, Tamaulipas, Mexico.

Barrientos-Lozano L. 2005. Clasificacion de los Orthoptera: Caelifera, sensustricto)-especies plaga en Mexico, pp. 1-25. In: Barrientos-Lozano L., Almaguer-Sierra P. (Eds) Memoria 2do. Curso Internacional: Manejo Integrado de la Langosta Centroamericana (Schistocerca piceifrons piceifrons Walker) y Acridoideos plaga en America Latina. Cd. Victoria, Tamaulipas, Mexico.

Barrientos-Lozano L., Garcia-Salazar P., Avila-Valdez J. 2004. Evaluacion Tecnica y Situacion Actual del problema de la langosta Voladora (Schistocerca piceifrons piceifrons Walker) en la Huasteca, Noreste de Mexico. Entomologia Mexicana 3: 458-460.

Comision Nacional del Agua, 2000. Programa de Gran Vision 2000-2020. Gerencia Regional. Cd. Victoria, Tamaulipas. Mexico.

Direccion General de Sanidad Vegetal/Servicio Nacional de Sanidad Vegetal, Inocuidad y Calidad Agroalimentaria. 2003. Memoria del Curso Regional sobre la Langosta (Schistocerca piceifrons piceifrons). Campo Experimental Ebano, San Luis Potosi. CIRNE-INIFAP-SAGARPA.

Higley G.L., P. Pedigo, K.R. Ostle. 1986. DEGDAY: a program for calculating degree-days, and assumptions behind the degree-days approach. Environmental Entomology 15: 999-1016.

INEGI.1983. Sintesis Geografica del Estado de Tamaulipas, Mexico, Distrio Federal.

Kauffman W.C.R., Flanders V., Edwards C.R. 1985. Population growth potential of Mexican bean beetle Epilachna varivestis Mulsant (Coleoptera: Coccinellidae) on soybeans and lima bean cultivara. Environmental Entomology 14: 674-677.

Mellors W.K., Bassow F.E. 1983. Temperature dependant development of Mexican bean beetle (Coleoptera: Coccinellidae) immatures on snap beans and soybean foliage. Annals Entomological Society of America 76: 692-698.

Pinto V.M., Vera G.J., Landois P. L.L., Leyva V.J.L. 2002. Simulacion de la dinamica poblacional de la conchuela del frijol Epilachna varivestis MULS., mediante un modelo fenologico de desarrollo acumulativo. Agrociencia 36: 115-122.

Pigliucci M. 2001. Phenotypic Plasticity: Beyond Nature and Nurture. Johns Hopkins University Press, Baltimore, MD.

Poot PM. 2005. Compuestos volatiles y extractos cuniculares de la langosta centroamericana (Schistocerca piceifrons piceifrons Walker), como posibles inductores de la gregarizacion, pp. 74-79. In: Barrientos-Lozano L., Almaguer-Sierra P. (Eds) Memoria 2do. Curso Internacional: Manejo Integrado de la Langosta Centroamericana (Schistocerca piceifrons piceifrons Walker) y Acridoideos plaga en America Latina. Cd. Victoria, Tamaulipas, Mexico.

Porter J., Parry M., Carter T. 1991. The potential effects of climatic change on agricultural insect pests. Agricultural Forest Meteorology 57: 221-240.

Retana J. 2003. Relacion entre la temperaturas superficial del mart' anomalias de temperatura del aire en el Pacifico norte durante ano ENOS, como posible predictor de potencialidad de plaga de langosta. Topicos de Meteorologia y Oceanografia 10: 31-35.

Rodriguez-Absi J. 1997. Agroecologia Cuantitativa. Comite Estatal de Sanidad Vegetal del Estado de Sinaloa.

Rodriguez-Absi J., Ornelas-Gutierrez E., Rodriguez-Fuentes H. 2007. Dinamica de sistemas de pastoreo intensivo para la produccion de leche. Editorial Trillas S. A. de C. V. Mexico. In press.

UC-IPM Online: www.ipm.ucdavis.edu/ WEATHER/ddconcepts.html. Date accessed: 26-12-2008.

Uvarov B.P. 1935. Locust and Grasshoppers Handbook for their Study and Control. London, LI.K. The Imperial Bureau of Entomology: 69-169; 263-273.

JOSE RODRIGUEZ-ABSI, PEDRO ALMAGUER-SIERRA, LUDIVINA BARRIENTOS-LOZANO, HUMBERTO RODRIGUEZ-FUENTES

(JR-A) Junta Local de Sanidad Vegetal del Valle de Culiacan, Sinaloa, Mexico. Email: roabsi@gmail.com

(PA-S, LB-L) Instituto Tecnologico de Cd. Victoria, Boulevard Emilio Portes Gil No. 1301. C. P. 87010. Cd. Victoria, Tamaulipas, Mexico. Email: ludivinab@yahoo.com

(HR-F) Universidad Autonoma de Nuevo Leon-Facultad de Agronomia-Division de Estudios de Posgrado e Investigacion. Carretera Zuazua-Marin Km. 17.5. C. P 66700, Marin, N. L. Mexico.
Table 1. Meteorological stations located in south Tamaulipas,
Mexico. Comision Nacional del Agua (CNA-2000).

Meteorological          Lat North              Long West
Station

Aldama              22[degrees] 55'44"     98[degrees] 04'30"
Barberena           22[degrees] 37'15"     98[degrees] 10'15"
Chamal Nuevo        22[degrees] 50'30"     99[degrees] 11'30"
El Nacimiento       22[degrees] 57'47"     98[degrees] 07'41"
Gonzalez            22[degrees] 48'51"     98[degrees] 25'11"
El Refugio          22[degrees] 43'36"     99[degrees] 01'23"
Lazaro Cardenas     22[degrees] 29'56"     98[degrees] 49'30"
Ocampo              22[degrees] 50'40"     99[degrees] 19'54"
San Gabriel         23[degrees] 05'03"     98[degrees] 47'15"
Xicotencatl         22[degrees] 59'36"     98[degrees] 59'29"
El Apuro            23[degrees] 15'18"     97[degrees] 52'17"
El Lajal            22[degrees] 50'46"     98[degrees] 43'4G"
El Mayab            22[degrees] 54'36"     98[degrees] 20'44"
Gomez Farias        23[degrees] 01'43"     99[degrees] 08'45"
Mante               22[degrees] 43'36"     98[degrees] 58'39"
La Servilleta       22[degrees] 51'00"     99[degrees] 07'10"
Estacion Manuel     22[degrees] 43'31"     99[degrees] 18'30"
Nuevo Morelos       22[degrees] 31'49"     99[degrees] 12'50"
San Felipe          22[degrees] 00'00"     98[degrees] 50'57"
El Oyul             22[degrees] 33'00"     99[degrees] 05'12"

Meteorological           Altitude             Mean annual
Station                meters a.s.l         Precipitation mm

Aldama                     130                    959.4
Barberena                   66                    957.7
Chamal Nuevo               108                   1210.7
El Nacimiento              140                    836.4
Gonzalez                    55                    899.5
El Refugio                230                    NA *
Lazaro Cardenas             G7                    943.1
Ocampo                     320                    1544
San Gabriel                140                    1950
Xicotencatl                100                    1023
El Apuro                    45                    901.6
El Lajal                    80                    783.4
El Mayab                   120                    935.9
Gomez Farias               380                   1842.3
Mante                      100                   lO16.5
La Servilleta               94                   1304.2
Estacion Manuel             80                    840
Nuevo Morelos              290                   lO62.3
San Felipe                  68                    966.9
El Oyul                    NA *                  1038.7

NA * = not available

Table 2. Calculated thermal time ([degrees]C-days) and
Diapause Cool Hours (DCH) (T[less than or equal to] 15.3
[degrees]C), for 20 meteorological stations located in south
Tamaulipas, Mexico

Meteorological       ([PSI] yearly)    Diapause Cold Hours
Station             [degrees]C-days      (DCH) November
                                       15th to April 10th
                                        T<15.3 [degrees]C

Aldama                   3389.9               1925
Barberena                3827.1               1655
Chamal Nuevo             3874.1               1913
El Nacimiento            3424.3               1892
Gonzalez                 3789.5               1900
El Refugio               3932.4               2018
Lazaro Cardenas          3996.8               1857
Ocampo                   3470.3               20G5
San Gabriel              3715.9               2039
Xicotencatl              4272.3               1908
El Apuro                 3343.5               1773
El Lajal                 4150.5               1850
El Mayab                 3418.4               20G3
Gomez Farias             3311.2               1941
Mante                    3916.3               2038
La Servilleta            4041.1               1887
Estacion Manuel          4062.7               1765
Nvo. Morelos             4202.6               1927
San Felipe               4036.5               1873
El Oyul                   NA *                1985
                        3798.71              1913.70
       SD                314.93              105.76

NA * = not available
COPYRIGHT 2009 The Orthopterists' Society
No portion of this article can be reproduced without the express written permission from the copyright holder.
Copyright 2009 Gale, Cengage Learning. All rights reserved.

Article Details
Printer friendly Cite/link Email Feedback
Author:Rodriguez-Absi, Jose; Almaguer-Sierra, Pedro; Barrientos-Lozano, Ludivina; Rodriguez-Fuentes, Humber
Publication:Journal of Orthoptera Research
Article Type:Report
Geographic Code:1MEX
Date:Jan 1, 2009
Words:3871
Previous Article:Proventriculus of three nemobiinae crickets (Orthoptera: Grylloidea: Trigonidiidae).
Next Article:Annotated check-list of Orthoptera of Libya.
Topics:

Terms of use | Privacy policy | Copyright © 2018 Farlex, Inc. | Feedback | For webmasters