How to Use a Dichotomous Key

A dichotomous key, the type used in this knowledgebase, consists of a series of paired descriptions, called couplets. Beginning with the first pair of descriptions, read each thouroughly. Then examine the specimen and decide which description is most appropriate. In a printed dichotomous key you will find at the end of each description either a name or a number, indicating the next couplet to examine. In the computerized dichotomous key also provided here, you simply click on the graphic to move to the next couplet or the species or group identified.

Continue in this manner until all the couplets have been exhausted, or until you reach a conclusion as to the identity of the specimen. Writing down the numbers of the couplets you go to in the key may help define problem areas in case an incorrect identification is made. The identification key presented in this knowledgebase was prepared for use in identifying only those species presented here. As there are thousands of thrips species, be aware that using this key on a species outside the key's range will result in erroneous identification.

The identification key was designed with farmers, field scouts and non-entomologists in mind. The main characteristics are observable through a good hand lens. Be sure to use at least 14x magnification, although 20x is preferred. The first few times this key is used, specimens should be killed in 70% ethyl or isopropyl alcohol (available in all drugstores), so as to immobilize them. Once the user has become familiar with the characteristics that will separate the local vegetable thrips species, identification of living specimens in the field may be possible. Although such field identifications provide the most timely information, the likelihood that more than one species may be present should be taken into consideration before instituting a management program. In cases where such multiple infestations are likely, collecting large numbers of infested blooms or leaves into alcohol, and examining the thrips under a dissecting microscope with 10-40x magnification will provide more accurate information efficiently. The same characteristic used for field identifications can be used to sort large numbers of thrips when using a dissecting microscope.