Haller's organ:

an oval organ on the tarsus of ticks.

haemorrhage:

discharge of blood from blood vessels.

hair loss:

significant loss of hair resulting directly or indirectly from a disease process.

hamulus:

large hooks on the opisthaptor of Monogenea.

hemimetabolous:

developmental pattern in Insecta, in which a series of nymphal stages are produced.

hermaphrodite:

an individual possessing male and female reproductive systems (not necessarily simultaneously).

heteroxenous:

a life cycle in which more than one host individual is parasitized.

hexacanth:

a six-hooked embryo of cestoda.

histopathology:

microscopic abnormalities in cell and tissue structure caused by external agents or disease, and their study.

holometabolous:

developmental pattern in Insecta, involving larva and pupa.

homoxenous:

a life cycle in which only one host is parasitized.

hook:

a hard, curved structure, usually of complex shape, used for attachment of parasite to host.

host specificity:

the degree to which a parasite is capable of infecting and developing within only a limited number of host species.

hyaline:

clear and acellular.

hydatid:

a bladder larva of Cestoda characterized by internal (and often external) chambers lined by germinal epithelium.

hydrostatic skeleton:

a skeletal system in which support is derived by internal fluid pressure.

hypostome:

sclerotized, median, ventral mouthparts of ticks, often with recurved teeth used for attachment.