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Behavioral Ecology Behav Ecol Sociobiol (1987) 21:157-162 and Sociobiology ? Springer-Verlag 1987 The timing of calling, movement,and mating in the field crickets Gryllusveletis, G. pennsylvanicus,and G. integer B. Wade French and William H. Cade Departmentof Biological Sciences, Brock University, St. Catharines,Ontario, L2S 3A1, Canada Received December 23, 1986 / Accepted June 22, 1987 Summary. The temporal relationships between Methods and movement were studied in nat- mating, calling, G. integer commonly occurs in central Texas from spring to ural habitats at different densities in the field crick- fall and was studiedfrom April to August, 1986, at the Bracken- ets, Gryllusveletis, G.pennsylvanicus and G. integer. ridge Field Laboratory, The University of Texas, Austin. In There was variation between and within species, southern Ontario, G. veletis is sexually mature from May until but males showed increased at late July, whereas G. pennsylvanicusis sexually mature from generally calling until October G. veletis and dawn a decline early August (Alexander 1968). followed by during the day. Mat- G. pennsylvanicuswere studied on the campus of Brock Univer- ings were also more frequent at sunrise in most sity, St. Catharines, Ontario, from June to September 1983 observations, and male and female movement de- and 1984. clined near dawn. Female movement and sexual receptivityare closely related to levels of male call- Outdoor arenas ing and movement. All studies were carriedout in outdoor arenas placed in cricket natural habitats. Arenas were constructedof concrete walls (G. integer) or aluminum siding (G. veletis and G. pennsylvanicus) and measured approximately 13.5 x 13.5 x 1.2 m. The arenas contained naturally occurring grasses and other herbaceous Introduction plants which were routinely cut to a height of approximately 4 cm to facilitateobservations. To preventbird entry, the arenas The calling song of male field crickets attracts con- were completely covered with orchard bird netting supported females. Males also search for females in by posts. The mesh was large enough to allow crickets to enter. specific Plastic flags were used to divide the arena into 25 quadrats, the vicinity of calling males. Male searching and each approximately2.7 x 2.7 m. Cricket shelters were provided calling behavior apparently evolved in the context consisting of a hole in the soil approximately4 cm deep covered of male-male competition and female choice, and by a piece of plywood, 24 x 24 cm. One shelter was placed in males should call and search when females are the center of each quadrat. Flat stones approximately 12 x 12 cm were at the of a side of most Cade placed midpoint quadrat receptive (Alexander 1975; 1979a, adjacent to a wall. The soil was moistened daily since crickets 1980; Otte 1977; Walker 1983a). With few excep- require moist soil for oviposition and they drink water from tions (Forrest 1983; Walker 1983b), however, very the soil and vegetation. little is known about the relationship between fe- male and the of male receptivity nightly timing Collecting crickets cricket calling and searching behavior under field conditions. Very few observations have been con- G. veletis and G. pennsylvanicuswere collected as nymphs and ducted on crickets and other active an- adults in St. Catharines.Crickets were brought into the labora- nocturnally tory and kept at 25-30? C and 30-35% relative humidity. The imals throughout the night. The research reported photoperiod was 12 h light and 12 h dark. Females and male here was intended to test the hypothesis that the nymphs were housed in separate terraria. All terraria were timing of male searching and calling behavior checked daily for newly molted adults, and individual adult coincides with the of under males were placed in 500 ml cardboard cups. Food (Purina closely timing mating Cat vials of and shelter field conditions in the field veletis Chow?, lettuce), cotton-plugged water, crickets, Gryllus (egg cartons) were provided. G. integer were collected in the and G. pennsylvanicusin Ontario, and G. integer field or when attracted to taped broadcasts of G. integer song in Texas. or to electric street lights (Cade 1979a, b). Also, male and This content downloaded from 142.66.3.42 on Tue, 23 Jul 2013 15:10:33 PM All use subject to JSTOR Terms and Conditions 158 female G. integer routinely flew into the arena, probably in The linear distance travelledby males between surveyswas response to males calling within. One hind wing was removed used to assess movement as an indicator of searchingbehavior. from each male and female cricket, thus preventing G. integer Cricketshad to travel at least 60 cm in the arena before move- from flying out of the arena. Individual crickets were marked ment was scored. This was the minimum detectable displace- distinctively(Walker and Wineriter1981), but data on individ- ment allowed for transferringa cricket's location in the arena ual variationin mating behavior are reportedelsewhere (French to its location on the arena map. The movement of females 1986). Hindwing removal and marking has no effect on survi- was also determinedin the same manner, since female locomo- vorship or the duration of nightly calling of male G. integer tion and phonotaxis vary with sexual receptivity(Cade 1979c; (Cade unpublished).A series of observationsbegan by releasing Loher 1979a, b, 1981). males and females into the center or under randomly chosen burrowsof the arena about 3-5 h before sunset. The population density of G. integerwas maintained at approximately5 males Results and 5 females. Since population density may affect calling be- havior (Alexander 1961, 1968, 1975), two densities were used 24 h observations in G. veletis and G. pennsylvanicus:a low density of 5 males and 5 females and a relatively higher density of 20 males and Frequency distributions of matings, movement, 20 females. After an introduction the density was maintained and are in 1 for G. veletis at both densi- at approximatelythe initial level by adding previouslycollected calling Fig. crickets that were held temporarilyin the laboratory, or num- ties. There were too few matings at low density bering crickets that flew into the arena in G. integer.Attracted for statistical testing, but all matings occurred dur- G. integer were removed if not needed to maintain the appro- ing the day. Female movement and male calling priate density. Replicatesfor the same species at the same densi- were significantly different from random at low ties were performed as follows: 3 samples at low density of with most at and near sun- 9, 10 and 4 nights for G. integer; 1 sample of 10 nights at density activity night high density, and 2 samples of 10 nights each at low density rise. (Statistical data are summarizedin Table 1 for for G. veletis; 2 samples of 10 and 19 nights at high density, all populations). Male movement was randomly and 1 sample of 9 nights at low density for G. pennsylvanicus. distributed with respect to time in the low density The replicateswere combined for statistical analysis since most G. veletis did not samples had homogeneous variances(French 1986). populations. Matings vary signifi- cantly at high density in G. veletis. In contrast, female and male movement and the number of Observations and data collection callers were statistically different from random dis- Arenas were observed from 22.00 to 08.00 h (approximately 1.5 to 3 h past sunset to 2 to 3 h past sunrise). Sunset times Gryllusveletis were approximately19.53 h and sunrise times were approxima- I-I Low Density- 24 h 04.47 h local time for G. 19.15 h and 05.23 h local HighDensity - 24 h Matings A tely veletis, 6- 6 time for G. pennsylvanicus,and 20.00 h and 05.00 h local time for G. integer. These sunset and sunrise times were estimated from the average of the sunset and sunrise times on the first and last days of the month. A single observation over a com- plete 24 h cycle was also performed once for G. veletis and . G. at each At the of each I I.I.. pennsylvanicus density. beginning night a complete survey of the arena was conducted using a H30- | FemaleDisplacement B headlamp to ascertain each cricket's location. Crickets were readily visible under the shelters or in the grass. Locations of cricketswere marked on maps of the arena. A complete inspec- 153 i5 tion of the arena was made every h and a new map used to record cricket positions. Calling behavior was ascribed to a particular male if he was the only one in a given location at the previous and follow- Z 18- I Calling Males C ing check of male positions. If more than one male was in a shelter, it was possible to raise the shelter and, although the male stopped calling, observe which male had his wings still raised in the calling position. Males disturbedin this way usual- ly resumed singing after a few min. If calling was heard from a position where no male had been observed previously, we - 45 Sunrise n D identifiedthat male and marked his position on the map. Every MaleDisplacement 5 min we recorded the production of calling song for males of known identity. To determine the number of calling males 30 1I Sunset in each male who called for at least one 5 min interval h, any 15 was scored as a caller. This practice produces a conservative estimate of the total duration of calling. In all cases, however, males called during several of the 5 min intervalsavailable each 23 02 05 08 11 14 17 20 were considered to have occurred h (French 1986). Matings Time of when a copulation was observed or a female possessed a fresh Day (h) spermatophorewhile in the immediatepresence of a single male.

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