Handbook of Medical Entomology Part 33

h. Possessing a specially developed apparatus for clinging to hairs of mammals. LISTROPHORIDae.

hh. Without such apparatus.

i. Living on the plumage of birds. a.n.a.lGESIDae.

ii. In the living tissues of birds and mammals.

j. v.u.l.v.a longitudinal. In the skin and cellular tissues of birds. CYTOLEICHIDae.

This family contains two species, both occurring in the United States on the common fowl.

_Laminosioptes cysticola_ occurs on the skin and also bores into the subcutaneous tissue where it gives rise to a calcareous cyst. _Cytoleichus nudus_ is most commonly found in the air pa.s.sages and air cells.

jj. v.u.l.v.a transverse. In the skin of mammals and birds. SARCOPTIDae

k. a.n.a.l opening on the dorsum.

l. Third pair of legs in the male without apical suckers. On cats and rabbits. NOTDRES Rail.

The itch mite of the cat, N. CATI (fig. 61) has been recorded on man.

ll. Third leg in the male with suckers. On bats _Prosopodectes_ Can.

kk. a.n.a.l opening below.

l. Pedicel of the suckers jointed; mandibles styliform and serrate near the tip. PSOROPTES Gerv. P. COMMUNIS OVIS is the cause of sheep scab.

ll. Pedicel of the suckers not jointed; mandibles chelate.

m. No suckers on the legs of the females; parasitic on birds, including chickens. _C.

mutans_ is itch mite of chickens.

_Cnemidocoptes_ Furst.

mm. Suckers at least on legs I and II; parasitic on mammals.

n. Legs very short; in the male the hind pairs equal in size; body usually short.

SARCOPTES Latr.

S. SCABIEI is the itch mite of man (fig.

56).

[Ill.u.s.tration: 157. Amblyomma, female. After Nuttall and Warburton.]

nn. Legs more slender; in the male the third pair is much larger than the fourth; body more elongate.

o. Female with suckers on the fourth pair of legs. Species do not burrow in the skin, but produce a scab similar to sheep scab. They occur in the ox, horse, sheep and goat. CHORIOPTES Gerv. C. SYMBIOTES BOVIS of the ox has been recorded a few times on man.

oo. Female without suckers to the fourth legs.

p. Hind part of the male abdomen with two lobes. On a few wild animals.

_Caparinia_ Can.

pp. Hind part of the male abdomen without lobes. Live in ears of dogs and cats.

_Otodectes_ Canestr.

_O. cynotis_ Hering (fig. 150 e) has been taken in the United States.

ee. Palpi usually of four or five segments, free; rarely with ventral suckers near genital or a.n.a.l openings; eyes often present; tarsi never end in suckers; body usually divided into cephalothorax and abdomen; rod-like epimera rarely visible; adults rarely parasitic.

f. Last segment of the palpi never forms a thumb to the preceding segment; palpi simple, or rarely formed to hold prey; body with but few hairs. EUPODOIDEA.

g. Palpi often geniculate, or else fitted for grasping prey; mandibles large and snout like; cephalothorax with four long bristles above, two in front, two behind; last segment of leg I longer than the preceding segment, often twice as long. BDELLIDae.

gg. Palpi never geniculate (fig. 158a), nor fitted for grasping prey: beak small; cephalothorax with bristles in different arrangement; last segment of leg I shorter or but little longer than the preceding joint; eyes when present near posterior border. EUPODIDae

Moniez has described a species from Belgium (TYDEUS MOLESTUS) which attacks man. It is rose colored; eyeless; its legs are scarcely as long as its body, the hind femur is not thickened; the mandibles are small and the a.n.a.l opening is on the venter. The female attains a length of about 0.3 mm.

ff. Last segment of the palpus forms a thumb to the preceding, which ends in a claw (with few exceptions); body often with many hairs (fig. 158 k). TROMBIDOIDEA.

g. Legs I and II with processes bearing spines; skin with several shields; c.o.xae contiguous. CaeCULIDae.

gg. Legs I and II without such processes; few if any shields.

h. Palpi much thickened on the base, moving laterally, last joint often with two pectinate bristles; no eyes; legs I ending in several long hairs; adult sometimes parasitic. CHEYLETIDae

CHEYLETUS ERUDITUS, which frequents old books, has once been found in pus discharged from the ear of man.

hh. Palpi less thickened, moving vertically; eyes usually present; leg I not ending in long hairs.

i. c.o.xae contiguous, radiate; legs slender, bristly; body with few hairs; no dorsal groove; tarsi not swollen.

ERYTHRaeIDae.

ii. c.o.xae more or less in two groups; legs less bristly.

[Ill.u.s.tration: 158. (_a_) Tydeus, beak and leg from below; (_b_) Cheyletus pyriformis, beak and palpus; (_c_) beak and claw of Pediculoides; (_d_) leg of Sarcoptes; (_e_) scutum of female of Amblyomma americana; (_f_) leg I and tip of mandible of Histiostoma americana; (_g_) Histiogaster malus, mandible and venter; (_h_) Aleurobius farinae, palpus and leg I of male; (_i_) Otodectes cynotis, tip of abdomen of male, (_j_) beak and a.n.a.l plate of Dermanyssus gallinae; (_k_) palpus of Allothrombium. (_a_) to (_j_) after Banks.]

j. Body with fewer, longer hairs; often spinning threads; no dorsal groove; tarsi never swollen; mandibles styliform (for piercing). TETRANYCHIDae

The genus TETRANYCHUS may be distinguished from the other genera occurring in the United States by the following characters: No scale-like projections on the front of the cephalothorax; legs I as long or longer than the body; palp ends in a distinct thumb; the body is about 1.5 times as long as broad. T. MOLESTISSIMUS Weyenb.

from South America, and T. TELARIUS from Europe and America ordinarily infesting plants, are said also to molest man.

jj. Body with many fine hairs or short spines; not spinning threads; often with dorsal groove; tarsi often swollen.

k. Mandibles styliform for piercing. RHYCHOLOPHIDae.

kk. Mandibles chelate, for biting. TROMBIDIDae

The genus TROMBIDIUM has recently been subdivided by Berlese into a number of smaller ones, of which some five or six occur in the United States. The mature mite is not parasitic but the larvae which are very numerous in certain localities will cause intense itching, soreness, and even more serious complications.

They burrow beneath the skin and produce inflamed spots. They have received the popular name of "RED BUG." The names LEPTUS AMERICa.n.u.s and L. IRRITANS have been applied to them, although they are now known to be immature stages. (Fig. 44.)