672 . LAURA FLORENCE 
interpretation of the mouth parts. Owing to the specialized nature of 
the mouth parts and the lack of any ontogenetic proof of their homologies, 
various interpretations have been offered by investigators according to 
their views of the affinities of the group. 
The early naturalists of the latter half of the seventeenth century 
attributed sucking mouth parts to lice, and based their opinions on the 
experimental feeding of captive lice on themselves. Nitzsch (1818:304) 
confirmed the observations of Swammerdam as to the presence of a 
bristle sheath (not the true sheath, but the proboscis), and put forward 
the hypothesis that the inner tube of suction consisted of several setae. 
His drawings of the structure were published, not with the text, but 
posthumously by Burmeister (1838). A year later Erichson (1839:377) 
stated that previous workers had erred in their descriptions, and that 
the louse possessed no hooks on the haustellum but did have a pair of 
strong, four-jointed palpi and very distinct mandibles. This statement 
led to Burmeister’s (1847) paper upholding and confirming the opinions 
of Nitzsch, in which he gave an account of the structures in the hog louse. 
His work, though in the light of more recent investigations incomplete and 
in parts inaccurate, was a distinct addition to the knowledge of the subject. 
It was followed the next year by a contribution from Simon (1848:274), 
who, in his treatise on skin diseases, described his jot work with Erichson 
and corroborated Erichson’s statements as to the presence of true palpi 
and mandibles and the absence of a sucking apparatus. 
The controversy was finally settled in 1864, when Schjédte (1864, English 
trans. 1866:213) published the results of his investigations and his inter- 
pretations of the artifacts which had misled the supporters of the biting- 
mouth-parts theory. In the same year Landois (1864:3) described the 
mouth parts of Phthirius as corresponding very closely with Erichson’s 
and Simon’s descriptions of those of Pediculus capitis and P. vestimentt, 
but when he published the results of his investigation of the clothes 
louse (Landois, 1865 a:34) he stated that his first interpretation was 
wrong and that the mouth parts were of the sucking type. Briihl (1871) 
described the mouth parts of the three species affecting man, and 
along with Schjédte considered the piercing mouth parts as having arisen 
through a modification of the mandibles and the maxillae, a view which, 
according to Enderlein (1905:631), originated in 1853 with Gerstfeldt, 
who regarded the mandibles as a tube made up of two halves and the 
