The tendency to be attracted toward heat is called thermotaxis.
Documented cases
Thermotaxis has been documented in
- C. elegans
- Ploff and Sokut 2010
- Slime molds Meloidogyne incognita
- Pline et al 1988
- Drosophila
- Rosenweig et al. 2004
- Mosquito Aedes Aegypti
- Patterson and Brown 2009
- Lake sculpin (Cottus extensus) larvea
- Wurtsbaugh and Neverman 1988
- Mammalian sperm cells
- Bahat et al. 2003
The best documentation is on C.elegans. There are probably many undocumented species that display thermotaxis but those are the documented cases I could find.
Many of these species are easy to find in biology labs. Sperms cells are very easy to find especially if you are a male but it may take complex methodology to observe thermotaxis on cells. Bigger organisms are of greater interest.
Do you really need another species?
On a side note, I am wondering whether testing your device on a different species is of much interest to you. Testing the your device create a thermal gradient is sure of interest but one species may react very differently to a specific gradient than another one and it feels a priori to me that you'd be waisting your time by testing it on a different species.
I think it would be more interesting to just place thermometers along space and measure temperature to ensure that a gradient exists and make sure that the temperatures and steep of gradient are within the range of what schistosome may experience in nature.
But whether the test is a good idea was not part of your question. Also, I am not involved in this research and you may have good reasons of yours of testing your device on a different species.