Termites Tested 

We tested the attraction of termites to different doses of carbon dioxide in the laboratory. The experiments were conducted with field-collected termite workers of Reticulitermes tibialis Banks (from Colorado), Reticulitermes virginicus Banks (from Virginia), and Reticulitermes flavipes (Kollar) (from Michigan).

 Collecting R. tibialis from rangeland in Colorado.

Bioassay Apparatus

 The bioassays were conducted using a behavioral choice test. The choice-test apparatus was constructed from a glass T-tube that was modified by having each branch of the T bent downward (2.5 cm from the end) at a 45?° angle to form a pitfall trap. A cap (5 mm NMR cap) with a single pinhole in it was pushed over the end of each pitfall end and this was connected with thin Teflon tubing to a polyethylene syringe (35 cc). For each test, one syringe contained a defined concentration of CO2 in air and the other contained only ambient air (control). Both syringes were clamped onto a syringe pump that was adjusted to provide airflow of 1 ml/min into each choice arm of the bioassay apparatus. We used GC-MS-SIM (m/z 44) to measure and verify the CO2 concentrations.

 Bioassay T tube apparatus.

 Polyethylene syringes containing CO2 (treatment) or ambient air (control), clamped onto syringe pump.

Procedures

Termite workers (5) were carefully placed into a holding tube constructed by placing caps (NMR) over the ends of a 10 cm length of plastic straw. The termites were allowed to rest (settle down) before being introduced into the bioassay apparatus. During the test, five termite workers were introduced into the long end of the glass "T" shaped tube by sliding one end of the holding tube over the long end of the T tube. This allowed the termites to readily enter the bioassay choice test T tube. Once they reached the junction of the "T", they had a choice of moving towards the CO2 end, from which flowed a defined concentration of CO2 in air, or towards the control end, from which flowed ambient air (control).

We tested CO2 concentrations of 1, 2, 5, 10, 20, 50 and 500 mmol CO2 per mol air against ambient air, which had a CO2 concentration of 1 mmol/mol.

Introducing termites (in holding tube) to the end of the bioassay T tube.

Statistical Analysis. A minimum of 10 replications were conducted with each termite species for every CO2 concentration tested. For analysis, each replicate (group of five termites) was counted as a single experimental unit. Student???s t tests were conducted to determine significant differences between the number of termites recovered from the CO2 side and the ambient air side of the apparatus for each concentration of CO2 by using Minitab (Addison-Wesley Publishing Co. Inc., Reading, Massachusetts) with ?µ = 0.05.

Results 

Three subterranean termite species, Reticulitermes flavipes (Kollar), R. virginicus Banks and R. tibialis Banks, were attracted to a range of CO2 concentrations between 5 and 50 mmol/mol. The strongest attraction for these three termite species was observed between 5 and 10 mmol per mol CO2.

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