The hypopi have evolved morphological adaptations, such as attachment devices, to aid in phoresy.
The hypopi of the Hemisarcoptes cooremani (Acari: Hemisarcoptidae), formerly regarded as a phoretic species of the beetle Chilocorus cacti, has been shown to acquire fluids from the hemolymph of its beetle host suggesting a transition between a phoretic and a truly parasitic association (Houck & Cohen 1995).
Elzinga and Broce (1988) mentioned that house flies (Diptera: Muscidae) were so burdened with histiostomatid hypopi that they were unable to fly or exhibit normal behavior.
Hypopi (Acari: Histiostomatidae) on house flies (Diptera: Muscidae): a case of detrimental phoresy.
The immobile, immature hypopi were individually encapsulated, mostly in adipose tissue, and evoked only a mild inflammatory infiltration of predominately macrophages with some heterophilic granulocytes.
Key words: Hypodectes propus, hypopi, subcutaneous, avian, southern crowned pigeon, Goura scheepmakeri
The cross-sectioned hypopi were individually encapsulated and had no contact with each other.
1-3) During their sojourn within the host, the hypopi increase 10-fold in size (4,5) and become widely dispersed as a result of the migratory behavior of their hosts.
The hypopi persist and grow in the subcutaneous adipose tissue until the host reaches maturity and begins to incubate its eggs.
Hypopi are resting deutonymphs and because they are hormonally activated, presumably may exist in a bird for long periods.