Class Diplopoda
Class Diplopoda
The Diplopoda (Gr. diploo, double, two + pous, podos, foot) are commonly called millipedes, which literally means “thousand feet” (Figure 20-2). Even though they do not have that many legs, they do have a large number of appendages, since each abdominal somite has two pairs, a condition that may have arisen from fusion of pairs of somites. Their cylindrical bodies are made up of 25 to 100 somites. Their short thorax consists of four somites, each bearing one pair of legs.
The head bears two clumps of simple eyes and a pair each of antennae, mandibles, and maxillae. The general body structures are similar to those of centipedes, with a few variations here and there. Two pairs of spiracles on each abdominal somite open into air chambers that connect to tracheal air tubes. There are two genital apertures toward the anterior end.
In most millipedes the appendages of the seventh somite are specialized for copulatory organs. After millipedes copulate, females lay eggs in a nest and guard them carefully. Larval forms have only one pair of legs to each somite.
Millipedes are not as active as centipedes. They walk with a slow, graceful motion, not wriggling as centipedes do. They prefer dark, moist places under logs or stones. Most are herbivorous, feeding on decayed plant matter, although sometimes they eat living plants. Because they are slow-moving animals, many millipedes roll into a coil when disturbed. Many millipedes also protect themselves from predation by secreting toxic or repellent fluids from special glands (repugnatorial glands) positioned along the sides of the body. Common examples of this class are Spirobolus and Julus, both of which have wide distribution.
The Diplopoda (Gr. diploo, double, two + pous, podos, foot) are commonly called millipedes, which literally means “thousand feet” (Figure 20-2). Even though they do not have that many legs, they do have a large number of appendages, since each abdominal somite has two pairs, a condition that may have arisen from fusion of pairs of somites. Their cylindrical bodies are made up of 25 to 100 somites. Their short thorax consists of four somites, each bearing one pair of legs.
The head bears two clumps of simple eyes and a pair each of antennae, mandibles, and maxillae. The general body structures are similar to those of centipedes, with a few variations here and there. Two pairs of spiracles on each abdominal somite open into air chambers that connect to tracheal air tubes. There are two genital apertures toward the anterior end.
In most millipedes the appendages of the seventh somite are specialized for copulatory organs. After millipedes copulate, females lay eggs in a nest and guard them carefully. Larval forms have only one pair of legs to each somite.
Millipedes are not as active as centipedes. They walk with a slow, graceful motion, not wriggling as centipedes do. They prefer dark, moist places under logs or stones. Most are herbivorous, feeding on decayed plant matter, although sometimes they eat living plants. Because they are slow-moving animals, many millipedes roll into a coil when disturbed. Many millipedes also protect themselves from predation by secreting toxic or repellent fluids from special glands (repugnatorial glands) positioned along the sides of the body. Common examples of this class are Spirobolus and Julus, both of which have wide distribution.
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| Figure 20-2 A, A tropical millipede with warning coloration. Note the typical doubling of appendages on most segments, hence diplosegments. B, Head of millipede. |
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