io6 THE LEECHES OF MINNESOTA 



nuli. Eves usually 5 pairs, forming a marginal arch on somites II to 

 VI. Metameric sense organs usually conspicuous colorless spots on the 

 neural annuli, 6-8 above and 4-6 below. Cutaneous papillae small or 

 absent. Mouth large, occupying entire oral sucker; pharynx not pro- 

 trusible, usually preceded by three compressed, muscular, toothed jaws, 

 one dorsal and two ventro-lateral, the former alone, or all three 

 sometimes absent. Stomach with a single posterior pair of simple 

 caeca, or provided with one or two pairs of caeca in each segment ; no 

 intestinal caeca. Genital pores variable, the male usually on XII, female 

 on XIII and usually separated by 5 annuli; associated copulatory 

 glands may be present. Testes sacs usually 10 pairs belonging to 

 somites XIV-XXIII. Genital ducts complex, the male terminating in 

 an unpaired atrium with prostate gland and a usually filiform penis. 

 Ovisacs 1 pair, small pyriform, opening into an unpaired oviduct 

 terminating in a long vagina. Copulation occurs, during which the 

 penis of one individual implants spermatophores in the vagina of the 

 other. Eggs enclosed in vesicular or spongy chitinoid cocoons de- 

 posited in damp earth. Fresh water or more rarely terrestrial leeches, 

 which are voracious blood suckers or predatory destroyers of weaker 

 invertebrates. Mostly active swimmers. 



Genus Macrobdella Verrill. 



Size large. Dorsum marked by metameric red and black spots. 

 Jaws prominent each bearing numerous small teeth in a single series ; 

 gastric caeca very spacious, two pairs to each somite from X to XVIII. 

 Genital orifices separated by from 2 l /i to 5 rings, followed by the 

 two pairs of copulatory gland pores, which form a quadrate figure 

 opening in the furrows XIII/XIV and XIV bi/bj; penis short and 

 conical ; atrium and vagina both short, globoid. Active blood-sucker>, 

 attacking vertebrates. 



Macrobdella decora (Say) Verrill. 



(Plate IV, figs. 24, 25; Plate V, fig. 38) 



Hirudo decora Say (1824) 

 /Iirudo decora Leidy (1868) 

 Macrobdella decora Verrill (1872) 



Description. Macrobdella decora, the American medicinal leech, 

 reaches a length of eight to ten inches and a breadth of three-quarters 

 of an inch, but the examples most frequently met with arc much 

 smaller than this, while the largest may occassionallv exceed this size. 



