CLASS IV. ACAKI. Jgl 



Genus 1. TROMBIDIUM. Fair., Lair., Lcadi. 

 Lrgs eight. 

 Sp. ]. Trom. holoscriceum. Suliquadrate, hlood-red, tomentose; the 



down short composed of cyhndric i)ai)illa\ which arc rounded at 



their extremities. 

 Tromhidium holoscriceum. Fair., Latr. 

 Inhabits Europe, and is abundant in the spring. 



Genus 2. OCYPETE. Leach. 

 Legs six. 

 Sp. 1. Oc^. rubra. Red; back with a few long hairs, the legs with 



many short hairs of a rufous ash-colour; eyes black brown. 

 Ocypete rubra. Leach, Tram. Linn. Soc. xi. 



This curious little animal, which is not larger than a grain of 

 small sand, is parasitic, and is frequently to be found on the largest 

 tipuladous insects, adhering to their legs. No less than sixteen 

 specimens have been obtained from one insect. 



Fam. TI. Gammasid^^e. Tuach. 

 Palpi porrect, simple. 



Genus 3. GAMMASUS. Lafreil/e, Leach. 

 Bo'Ji/ depressed, the skin of the back partly or entirely coriaceous. 



* Anterior portion of the hack, and a triangular pai-t hcldnd, cori- 

 aceous. 



Sp. 1. Gumm. Coleoptrutorum. Coriaceous ])arts of the back fuscous ; 



anterior pair of legs a little longer than the hinder ones. 

 Gammase des Coleopteres. LMtr. Hist. Nat. des Crust, et dcs Insect. 



vii. 399. Gammasus Coleoptratorimi. Latr. Gen. Crust, et Insect, i. 



147. Leach. Acarus Coleoptratorum. Linn., Fahr. 

 Inhabits the excrements of horses and oxen, often attaching itself to 



Scarahai, Histcres, &c. in great numbers. 



** Back cntireli/ coriaceous. 

 Sp. 2. Gamm. marginatus. Ovate, lirown ; belly coriaceous, the sides 



alone membranaceous and whitish ; anterior legs nearly twice the 



length of the body. 

 Inhabits dung and dead animals. 



Fam. III. AcARiD.^. Leach. 



Mouth furnished with mandibles : palpi simple, very short, not por- 

 rectcd. 



Genus 4. ORIBITA. Latrcillc, Leach. 



Bodi/ covered by a coriaceous skin ; anterior part rostrated ; the pro- 

 duced part inclosing the organs of mastication : abdomen subglo- 

 bose : tarsi with claws. 



Sp. 1. Or. geniculatu. Fuscous-castaneous, shining, hairy : legs pale- 

 fuscous : thighs subclavate. 



