670 
.T. DAVIDSON. 
or tarsus consists of a small basal joint (6. ta.) and a longer, 
slightly curved, distal joint, which bears a pair of curved 
claws [cl.) and a few tactile hairs. 
The anterior pair of legs is the shortest, the mesothoracic 
legs being slightly longer, and the third pair the longest. 
A few hairs ai’e borne on each of the articles. 
The Abdomen. — The abdomen consists of nine visible 
segments.^ The terminal or ninth segtnent {ahd. ix) is very 
small, and is not prolonged into a cauda or tail, such as is 
found in many aphids. Situated below the terminal segment, 
opening on the dorsal surface of the body, is the anus {aoi.), 
immediately beneath which is the conspicuous anal plate (a. p.). 
This latter structure is an arched, lobe-like development of 
the integument, which extends beneath the anus aud the 
genital orifice, and bears numerous stout hairs. 
The transverse genital orifice {g. o.) is situated ventral to 
the anus, being overhung by the anal plate. On the ventral 
border of this opening the integument is developed to form a 
small semilunar-shaped genital plate {g. p.), which bears 
stout hairs. 
The abdominal spiracles are situated on the ventral surface, 
near the lateral margins of the body, in the wrinkled 
membranous chitin at the anterior borders of the first seven 
segments. 
• The number of segments in the abdomen of apliids is a disputed 
point, owing to the modification of the terminal segments. Balbiani 
(1869, p. 64) refers to the work of Lacaze-Duthiers (1853), ‘Recherches 
snr I’annure genitale femelle des Insectes,’ who considers that the 
typical number in insects is eleven. According to Buckton (1875, p. 20), 
this latter author has shown that in most Hemiptera there are three 
segments intervening between the genital orifice and the anus, and as 
Balbiani observes, the absence of the terminal segment in aphids must 
be attribrited to the atrophy of one of the post-genital segments. 
Kaltenbach (1843) considers there are only nine segments. Tullgren 
(1909) considers there are only nine visible in Schizoneura, and I have 
adoijted his terminology. 
