As some of you know, I am a graduate student at the University of Minnesota in the Department of Entomology. My focal species, however, is not an insect but an arachnid! More specifically, it is a mite. Here’s an adaptation of an exerpt from the introduction for my thesis proposal:

The mold mite Tyrophagus putrescentiae (Acari: Acaridae), is a stored product pest of economic significance that has been a problem in many types of food. This mite can cause significant damage to grains (Hughes 1976), cheese in cheese houses (Robertson 1952), cured ham (Arnau & Guerrero 1994) and pet food (Brazis et al. 2008). Recently, mites have been found in very large numbers infesting bagged dry (and semi-moist) dog food in grocery stores and other retail facilities. The mites burrow into and consume the kibble, destroying its quality. In addition to destroying food, there is evidence that the mite may be a source of allergens affecting dogs and humans (Brazis et al. 2008).

This mite is weakly sclerotized, which means its exoskeleton isn’t very hard, so it is prone to desiccation (drying out).  The mite collects moisture from the air via supracoxal gland and hygroscopic secretions in order to prevent desiccation (Wharton and Furumizo 1977). High relative humidity (>65%) is ideal for T. putrescentiae survival and reproduction/fecundity. Under ideal conditions mites have a generation time of 12.6 days and a population doubling time of 1.75 days, so they can quickly reach very large densities (Sánchez-Ramos and Castañera 2005).  The areas where this mite lives can be highly variable with regions of high and low humidity.  In areas of high humidity, rapid proliferation will occur when appropriate food sources are available. In areas of low humidity, the mites tend to clump together to avoid desiccation (Sánchez-Ramos and Castañera 2007).

Some other time I will talk more about dispersal behavior, since that will be what I will be studying. I will also be studying more about the effects of neryl formate, the alarm pheromone, which can cause escape behavior!

References & Other Resources

Arnau, J and L Guerrero. 1994. Physical methods of controlling mites in dry-cured ham. Fleischwirtsch 74:1311–1313.

Brazis, P, M Serra, A Sellés, F Dethioux, V Biourge and A Puigdemont. 2008. Evaluation of storage mite contamination of commercial dry dog food. Vet Dermatol. 4: 209-214. doi: 10.1111/j.1365-3164.2008.00676.x

Eaton, M and S A Kells. 2009. Use of vapor pressure deficit to predict humidity and temperature effects on the mortality of mold mites, Tyrophagus putrescentiae. Exp Appl Acarol. 47: 201–213. doi: 10.1007/s10493-008-9206-2

Hughes, A M. 1976. The mites of stored food and houses. Technical bulletin of the ministry of  agriculture, fisheries and food 9, Her Majesty’s Stationery Office, London. 400 pp.

Robertson, P L. 1952. Cheese mite infestation: an important storage problem. J Soc Dairy Technol 5: 86–95. doi:10.1111/j.1471-0307.1952.tb01555.x

Sánchez-Ramos, I and P Castañera. 2005. Effect of temperature on reproductive parameters and longevity of Tyrophagus putrescentiae (Acari: Acaridae) Exp Appl Acarol 36: 93–105. doi: 10.1007/s10493-005-0506-5

Sánchez-Ramos, I and P Castañera. 2007. Effects of relative humidity on development, fecundity and survival of 3 storage mites. Exp Appl Acarol 41: 87-100. doi: 10.1007/210493-007-9052-7

Wharton G W and R T Furumizo. 1977. Supracoxal gland secretions as a source of fresh water  for Acaridei. Acarologia 19: 112–116.