Silverfish.

Antennae short, composed of 12 or 13 segments; female without a projecting ovipositor :

Superfamily Sphecoidea (thread-waisted wasps) (figure 46).

43. Tip of abdomen with two or three long appendages directed backward............................. 44.

Tip of abdomen without such appendages ............................................................................... 45.

44. Abdominal appendages thick, rigid, in the form of forceps ;

Order Dermaptera, in part (earwigs).

Abdominal appendages delicate, flexible, antenna-like;

Order Thysanura (silverfish, etc.) (figure 47).

45. Tarsus composed of only one to three segments................................................................. 46.

Tarsus composed of four or five segments.............................................................................. 50.

46. Antennae conspicuous, projecting in front of head ............................................................. 47.

Antennae very short, inconspicuous, not projecting in front of head ........................................ 49.

Antennae composed of three to six segments............................................................................. 48.

Antennae with more than six segments; very tiny insects that sometimes occur by the thousands in damp houses ;

Corrodentia (psocids) (figure 48).

48. Mouth parts in the form of a distinct beak; body greatly flattened ;

Order Hemiptera, Family Cimicidae (bed bugs) (figure 49) .

Mouth parts not in the form of a beak; body not flattened.

Order Collembola (springtails) (figure 50).

49. With biting mouth parts . . . Order Mallophaga (biting lice) (figure 51).

With piercing and sucking mouth parts;

Order Anoplura (sucking lice) (figure 52).

50. Antennae prominent.............................................................................................................. 51.

Antennae inconspicuous, not projecting ..................................................................................... 52.

51. Body noticeably constricted at base of abdomen, antennae elbowed, the basal segment very long; tarsus five-segmented ;

Order Hymenoptera, Family:

Formicidae (ants) (figure 53, wingless form);

Body not constricted at base of abdomen; antennae not elbowed, basal segment short; tarsus four-segmented ;

Order Isoptera (termites) (figure 54, wingless form).

Bed Bug.

Flea.

52. Body strongly compressed from the sides; abdomen distinctly segmented; coxae very large and strongly flattened; legs fitted for jumping;

Order Siphonaptera (fleas) (figure 55).

Body not compressed; abdomen not distinctly segmented; legs not fitted for jumping :

Order Diptera, in part; wingless forms (sheep-tick and its relatives).