A PRELIMINARY STUDY OF THE ATTRACTIVENESS OF OVITRAP CUPS IN COLLECTING CONTAINER SPECIES IN MASSACHUSETTS

TIMOTHY D. DESCHAMPS, Executive Director

Central Mass. Mosquito Control Project

111 Otis Street Northborough, Massachusetts 01532

ABSTRACT

Using ovitraps to collect species data and to test for efficacy is a technique that has been well documented in many areas of mosquito control and research. A quick search on the Google website (www.google.com) using “Mosquito+Ovitrap” as the keywords turns up a wealth of information. In 2005 we employed ovitrap cups following the US Public Health Service & the Air Force Institute for Operational Health guidelines. Results were not entirely surprising, with Oc. j. japonicus as the predominant species, although Oc. triseriatus did not appear as anticipated, nor were any Culex identified. Ovitraps may be employed in the future by CMMCP to monitor population trends among the container species and for adulticide efficacy studies.

INTRODUCTION

The goal at CMMCP this year was simple and straightforward – will mosquitoes use ovitraps if presented, and what species will we expect to sample? Can ovitraps be used as a device to monitor container species and check for adulticide efficacy?

MATERIALS & METHODS

Ovitraps have been used at CMMCP in the past using coffee cans and seed germination paper. Dark colors are preferred by many container species of mosquitoes for oviposition (AFIOH website, Surveillance Methods/Ovitrap Collections). The coffee cans were painted black, but a source of seed germination paper can be hard to find once available stock is used up. To save on labor and to use materials readily available, the ovitraps will be designed according to the standards written by the US Public Health Service (figure 1). Black plastic cups with the CMMCP logo and “Mosquito Ovitrap” printed on the front were secured. Standard 6” hardwood tongue depressors and 8” natural (unbleached) paper towels were used to make the ovipaddle. A section of paper towel 8” square was cut and folded in half, then wrapped around the tongue depressor and secured at the top and bottom with office staples. A quarter-inch hole should be drilled in the cup 3.5 inches up from the bottom to prevent rainwater from overfilling the ovitrap. The cups may need to be secured in the area using a variety of methods such as a stone on the bottom, wired to a tree, etc.

10 ovitraps were placed in a wooded area with other container-breeding sources such as tarps, cans, etc. Each cup was filled with approximately 10 ounces of water from a nearby pond, and the cups were allowed to season for 1 week without the ovipaddle. After 1 week, the ovipaddles were placed in the cups and allowed to remain for 2 additional weeks. After 2 weeks the ovipaddles were collected, and the larvae present in the cups was placed in a single breeding chamber and reared to adult to determine species (table 1). The ovipaddles were allowed to desiccate and then the egg clusters on each ovipaddle were counted (table 2).

Several ovipaddles were submerged in water at a later date to encourage the eggs to hatch with the intent of identifying these to species. However most of the eggs did not successfully hatch, possibly due to extreme desiccation or exposure to high temperatures. The Air Force Institute for Operational Health recommendations are to place each ovipaddle in a sealed plastic bag, which should slow desiccation if the intent is to hatch at a later date (AFIOH website, Sorting, Packaging and Shipping Specimens).

Table 1:

ADULT IDENTIFICATION OF ALL HATCHED LARVAE IN OVITRAPS

Oc. j. japonicus (11 male, 13 female)

Table 2:

OVIPADDLE EGG COLLECTION COUNT
PADDLE 1: 350+	PADDLE 6: 350+
PADDLE 2: 275+	PADDLE 7: 175+
PADDLE 3: 200+	PADDLE 8: 350+
PADDLE 4: 250+	PADDLE 9: 250+
PADDLE 5: 200+	PADDLE 10: 350+
AVERAGE PER CONTAINER – 275

CONCLUSION

As expected, Oc. j. japonicus dominated the collections. This species prefers cleaner water with less tannins than their counterparts Oc. triseriatus and Culex (Rutgers University, New Jersey Mosquito/Biology & Control website), and the pond water used would favor this species. If collections of Oc. triseriatus and Culex are the intended targets as well as Oc. j. japonicus, then water containing bacteria and tannins such as a hay infusion used in gravid traps should be used in the ovitraps.

Gravid females seemed to prefer to oviposit the eggs on the folded margins and on the dimples present on the oviposition substrate. The ovitraps collected an average of 275 eggs each over a 2 week period, and may be a useful device to monitor efficacy and to check for population trends among the container species especially if hay infusion water is used. The ovipaddles could also be collected and stored to be hatched at a later time for species composition, educational demonstrations, to check for larvicidal product efficacy, etc.

REFERENCES

Air Force Institute for Operational Health (AFIOH) website:

http://www.brooks.af.mil/afioh/Health%20Programs/rsrh_ent_methods.htm

Rutgers University, New Jersey Mosquito/Biology & Control website:

http://www-rci.rutgers.edu/~insects/njspp.htm

PICTURES

This is a picture of the ovitrap cup designed for this study.
This is a picture of the ovipaddle after use. Note the black “specks” which are egg clusters.
This is a close-up of the ovipaddle. Note the egg clusters, especially on the dimples of the paper towel.
This is the location of the ovitraps, on the back of an abandoned pickup truck. This truck was in a wooded setting, and had a tarp holding water and breeding mosquitoes.