Phoretic relationships involving terrestrial arthropods are well documented (Lloyd et al., 1975; Zeh and Zeh, 1994; Gonzales et al., 2008). There are, however, fewer documented examples of phoretic relationships involving aquatic arthropods (Dosdall and Parker, 1998; Pennuto, 1997). Recorded examples of aquatic phoretic relationships include the protozoan Epistylis sp. on the exoskele ton of a fresh water crayfish, Cherax tenuimanus, as well as species of Simulium (Diptera: Simuliidae) on mayfly and dragonfly nymphs (Villarreal and Hutch ings, 1986; Burton and McRae, 1972). Phoresy is primarily a dispersal mechanism, but it can also facilitate reproduction as in the case of the parasitic wasp, Dimorphothynnus haemorrhoidalis (Hymenoptera: Tiphiidae) (Matthews and Matthews, 2010). During April 2007, we collected an immature Calopteryx sp. (Odonata: Calopterygidae) with a Hydra sp. (Anthomedusae: Hydridae) attached to its dorsum in Burd Run, Shippensburg, Pennsylvania. This is the first record of phoretic behavior by Hydra sp. The specimen was prepared for scanning by electron micro scope (SEM) examination using standard techniques (Stadtlander, 2007) i.e. dehydration through a series of ethanol concentrations, critical point drying, and sputter-coating with gold. The micrographs (Figure 1) clearly show that the Hydra sp. is attached by its basal disc near the base of the wing pads of the damselfly in a location that would probably not impede the mobility of the damselfly. The permanence of this relationship is not determined. A moulting event could easily dislodge the Hydra sp. from the damselfly. However, the Hydra sp. is well located to switch to the newly emerged Calopteryx sp. The nature of the relationship between these two species is also unclear, but it is possible that the Hydra sp. may benefit from the relationship in a manner similar to that hypothesized by Dosdall and Parker (1998) for the phoretic association between Nanocladius branchicolus (Diptera: Chironomidae) and Argia moesta (Odonata: Coenagrionidae). They suggested that the relationship benefited N. branchico lus by reducing interspecific competition for food, and reducing energy expenditure associated with relocation. Hydra spp. are relatively sedentary, typically found on rocks and vegetation. Łomnicki and Solbodkin (1966) describe an interesting mode of locomotion in response to overcrowding or lack of food where Hydra sp. produces a bubble and floats to the surface of the water to move short distances in relatively still waters. Much like the floating behavior, Hydra 154 ENTOMOLOGICAL NEWS