ANATOMY AND PHYSIOLOGY 67 
abdominal mass, the remaining segments being reduced and 
inconspicuous. The terminal segments of the abdomen often 
telescope into one another, as 1n eroG, 
many Coleoptera and Hymenop- 
tera (Chrysidide), or undergo 
other modifications of form and 2 
position which obscure the seg- 
mentation. As to the number of 7 
evident (not actual) abdominal 
segments, Coleoptera show five or 
six ventrally and seven or eight & 
dorsally; Lepidoptera, seven in vat 
ais 
the female and eight in the male; 
Diptera, nine (male Tipulidz) or 7 
only four or five; and Hymenop- 
tera, nine (Tenthredinidze) or as 9 
few as three (Chrysidide). In 
the larvze of these insects, how- 
ever, nine or ten abdominal seg- 
ments are usually distinguishable, CE 
though the tenth is frequently 
modified, being in caterpillars 
united with the ninth. 
Appendages.—Rudimentary ab- Ventral aspect of the abdomen 
: : . 5 of a female Machilis maritima, to 
dominaldimbs‘occurin Thysanura som xidimentacy limbs (a)! .68 
(Machilis Fig. 7 Ns Functional segments two to nine. (The left 
4 oS / appendage of the ninth segment is 
abdominal legs do not occur in omitted.) c, c, ¢, cerci—After 
adult insects, but in larvee the ab- °°" ™*** 
dominal pro-legs (often called “ false legs,’ Fig. 64) are ho- 
mologous with the thoracic legs and the other paired segmental 
appendages, as the embryology shows. The embryo of G:can- 
thus, according to Ayers, has ten pairs of abdominal appen- 
dages (Fig. 196), equivalent to the thoracic legs. Most of 
these embryonic abdominal appendages are only transitory, but 
the last three pairs frequently persist to form the genitalia, as in 
