1. Syd Bliss and Anne Haley
    Activity Levels and Environmental Preference of House crickets Under Various Light and Humidity Conditions
Syd Bliss and Anne Haley

2. Influence on resting place
Many abiotic factors influence choice
Testing light and humidity preferences
House crickets (Acheta domesticus)
Preferences, behaviour, eventual choice of resting place
House crickets easy to maintain, used in many studies as a general model for all crickets

3. Hypothesis
Null: crickets show no preference and no behaviour change in relation to light and humidity
Alternate: crickets show preference and behaviour change in relation to light and humidity

4. Predictions
Previously shown preference for dark enclosed spaces (Keiruzel 1976)
Water essential to invertebrate survival
Biochemical gradients, membrane fluidity, sustained periods of activity (Mcluney & Date 2008)
prefer dimly lit areas as a resting place and would consequently show less activity in these areas, avoid bright open spaces
Invertebrates living in desiccating habitats may show a decrease in these vital functions as a result of water loss (Mcluney & Date 2008).

5. Other factors Light is a cue in entrained rhythms
Affected by photoperiod, seasonal change and environmental response
*Difficult to maintain photoperiod, loosely based on 12:12 rhythm
Circadian rhythms to environmental cycles, seasonal development in response to photoperiod

6. Calls occur at night Stridulations function in: Mating Female choice
Sexual selection
Male aggression
Could affect choice in light vs. dark
Convey messages to conspecifics, related to light because occur at night?

7. Influences Innate responses Supplemented by
photo and thigmo-kinetic stimuli
Light and contact stimuli
Hygrophilia and thermophilia
Affinity for moisture and heat
Innate response: occurs automatically
These factors isolated in a lab setting

8. Methods Maintenance, manipulation and analysis
Obtained from Danielle, original shipment of males and females
Methods
Maintenance, manipulation and analysis

9. Maintenance Checked 3 times a week
Food and water replenished as needed
3 weeks under rough 12:12 photoperiod

10. Maintenance of crickets
30 adult males separated
Glass tank at room temperature
Layer of mulch and egg carton shelters
Dog food and apple slices
Moist sponges

11. Manipulation of Environment
Light preferences:
15 W, 40 W and 100 W
Desk lamp and garbage bag
Three light bulbs to test effect of light
One half covered by garbage bag, one light angled

12. Manipulation of Environment
Humidity preferences:
Desiccant of calcium chloride
Wet paper towel
Studies done under red light
Avoid effects of white light

13. 24 lines 1 cm apart drawn 1 cm across width of tank
Setup:
24 lines 1 cm apart drawn 1 cm across width of tank
Paper divider taped to sides of tank
Crickets could still travel underneath

14. Analysis of behaviour One cricket to test each factor to reduce errors
Acclimatization period of 10 minutes
15 replicates, two minute period to test factor (5 per light bulb)

15. Analysis of behaviour Two minute timer Counted number of lines crossed
Amount of time spent in half of tank measured
Number of lines: demonstrate behaviour in that specific factor
Amount of time spent in tank: shows preference

16. Analysis of behaviour
One person monitored light half while other person monitored dark half
Same procedure for humidity factors
No changes in level of desiccant or humidity

17. RESULTS Light – activity 15W mean lines crossed:
light section = (±4.55)
dark section = (±5.45)
no significant difference
(independent t-test, t=0.93,
df=8, p=0.38)
40W mean lines crossed:
light section = 9.20 (±5.11)
dark section = 8.20 (±5.14)
(independent t-test,
t=10.14, df=8, p=0.89)
100W mean lines crossed:
light section = (±9.60)
dark section = 8.40 (±1.98)
no significant difference
(independent t-test, t=-0.61, df=8, p=0.57)
Used 3 different light levels – 15W, 40W, 100W

18. Light – time budget 15W mean time: 100W mean time:
light section = sec (±10.46) (54.27%)
dark section = sec (±10.41) (45.72%)
no significant difference
(independent t-test, t=0.70, df=8, p=0.50)
40W mean time:
light section = 69.0 sec (±23.26) (57%)
dark section = 51.0 (±23.26) (42.5%)
(independent t-test, t=-0.55,
df=8, p=0.60)
100W mean time:
light section = sec (±14.90) (16.8%)
dark section = sec (±14.90) (82.2%)
significant difference
(independent t-test, t=3.78, df=8, p=0.0054)

19. Humidity – activity
Dry Section:
Mean lines crossed = 8.33 (±3.79)
Medium Section:
Mean lines crossed = 2.53 (±1.64)
Humid Section:
Mean lines crossed = 1.46 (±1.52)
no significant difference (ANOVA, F=2.26, df=2, p=0.12)
Post-hoc testing (Tukey HSD): no significant difference between the conditions

20. Humidity – time budget Dry Section:
Mean time= sec (±9.94) (81.17%)
Medium Section:
Mean time= sec (±7.19) (12.17%)
Humid Section:
Mean time= 8.00 sec (±7.75) (6.66%)
significant difference (ANOVA, F=36.34, df=2, p=5.75x10-10)
Post-hoc testing (Tukey HSD): significant difference between medium vs. dry (p=0.00) and humid vs. dry (p=0.00), no significant difference humid vs. medium (p=0.82)

21. Discussion
Photo: Jeff Morgan
Investigating how crickets choose to spend their time (resting place) based on 2 environmental abiotic factors
Light + activity: intensity of light does not affect the activity level of crickets
In contrast to other studies that reported House crickets having very distinct levels of locomotor activity under during light conditions, and activity peaks during darkness/ lowest light level available (Harker 1961; Nowosielski & Patton 1963; Cymborowski 1969, 1970; Azarin & Tyshchenk 1970; Kieruzel 1976).
So what do these results actually mean?
On average, 74% of daily activity of crickets occurs during darkness

22. Not entrained on L:D rhythm Not given adequate time to adjust to
Light + time budget: intensity of light does not affect the time budget of crickets, except when there is a extreme difference between the light level and darkness
In contrast to other studies that reported studies prefer darkness over light – negative phototaxis (Federhen 1955; Kieruzel 1976)
Not entrained on L:D rhythm
Not given adequate time to adjust to
changing conditions before time
budgets were measured
- Why our study did not find increased activity levels in darkness or preference for darkness may be due to a variety of reasons. In our experiment the crickets were not entrained on a regular L:D rhythm due to resource and time constraints. This may have affected the results and explain why the crickets did not react to different light levels as expected, with regard to both activity and light level preference.
In several other studies, if a cricket was not entrained on a rhythm prior to the study it was not included in the study. We were unable to do this due to time and resource constraints
In other studies, crickets were given almost a week in a new light level before anything was measured. Out study only allowed 10 minutes
Photo: Ralph Neale

23. Humidity + activity: humidity does not affect activity levels
Humidity + time budget: crickets preferentially seek out dry environments
Inconsistencies in previous studies:
Ghouri and McFarlane (1958) – prefer dryness
Kieruzel (1976) – prefer humidity
Humidity preferences in general have not widely been demonstrated in most insects – may be confounded with temperature
These inconsistencies make our results difficult to interpret.
Is has been suggested that insects – animals with high desiccation resistance - do not require a fine-scale humidity preferences (Hayward et al. 2000), and this may explain the ambiguities in previous literature in relation to this factor. Furthermore, temperature may be a confounding factor related to humidity, and it was not controlled for in our study or others
Additionally, some studies have found that some species have a humidity preference, but only when temperatures are high.
Photo: Milou Diable
Photo: Luiz Fernandez Garcia