Another species of Acarus, A. sac´chari, is found abundantly in ordinary moist sugar. If a little of the sugar be placed in a wine-glass, some water added, and the mixture be stirred until the sugar is dissolved, the Acari will be found both in the sediment and floating on the surface.

A somewhat larger member of the order occurs as a parasite upon a species of Dung-beetle (Geotrúpes stercorárius) which is vulgarly known as the Lousy Watchman. The beetle is black, shaded with purple, about three-quarters of an inch long, and is found under cow-dung. The mites cling pertinaciously to the under parts of the beetle, and can easily be seen with the naked eye. They are whitish, with the mandibles, the sucker, and two claws very distinct; and the palpi are unattached to the labium, or free. These mites form the species Gam´asus coleoptrator´um. Another species, Gamasus telárius, is the red spider of the greenhouse.

Trombid´ium fuliginósum ([Pl. IX.] fig. 37 d) is a common red spider of gardens. It is of a scarlet colour, appearing velvety from the presence of a dense coat of feathery hairs (fig. 37 f). The palpi of this mite are large, free, the last joint but one ([Pl. IX.] fig. 37 a) being furnished with a claw, while the last joint is obtuse, and resembles a lateral appendage. The mandibles (fig. 37 b) are furnished with a sharp curved claw. The legs are long, especially the anterior pair, and terminated by two claws, with a delicate sucker-like appendage (fig. 37 c).

Another species of Trombidium, T. holoseric´eum, greatly resembling the last, is also found in gardens. It may be easily distinguished from the last by the club-shaped hairs (fig. 37 e) existing upon the body. The harvest-bug, which causes such irritation of the legs of persons who frequent corn-fields in the autumn, is also a species of Trombidium—T. autumnále.

PLATE X. [[PAGE 133.]]
Insects.
Fig.
1.Atropos pulsotorius: * natural size.
2.Aphis of Geranium: a, foot; b, anal tube; c, antenna.
3.Scales on wing of Apollo-butterfly.
4.Lithobius forcipatus.
5.Lithobius forcipatus, head of: a, antennæ; b, mandibles; c, labial palpi; d, labium.
6.Dytiscus marginalis, head of larva.
7.Young larva of Dytiscus marginalis.
8.Pupa of Gnat (Culex pipiens).
9.Larva of Gnat.
10.Head of Gnat, male.
11.Head of Gnat, female.
12.Coccinella 7-punctata (large Lady-bird), labium of.
13.Coccinella 7-punctata, mandible of.
14.Coccinella 7-punctata, labrum of.
15.Coccinella 7-punctata, antenna of.
16.Coccinella 7-punctata, maxilla of: a, palp; b, c, lobes of maxilla.
17.Head of Musca domestica (House-fly): a, antenna; b, labial palpi; c, proboscis.
18.Head of Stomoxys calcitrans: 18 a, antenna.
19.Scales of insects: a, scale of Podura; b, of House-moth (Tinea vestianella); c, of Podura; d, of Lepisma; e, hair of Podura; f, scale of Cabbage-Butterfly (Pontia brassicæ).
20.Head of Cabbage-Butterfly: a, antennæ broken off; b, palp; c, tongue (antlia); d, club of antenna.
21.Head of human Flea (Pulex irritans), female (♀): a, palpi; b, maxillæ.
22.Flea of the Rat (Pulex muris), male (♂).
23.Pterostichus (Steropus) madidus; 23 a, antenna.
24.Part of leg of Pterostichus madidus: a, tibia; b, tarsus.
25.Labrum of Pterostichus madidus.
26.Mandible of Pterostichus madidus.
27.Labium of Pterostichus madidus: a, mentum; b, labial palp.
28.Maxilla of Pterostichus madidus: a, claw; b, c, maxillary palps.
29.Proboscis of House-fly.
30.Larva of Flea.
31.Larva of Chironomos plumosus.
32.Foot of House-fly.
33.Eye of House-fly.
34.Leg of Ant (Formica fusca);
34*, pectinate process.