762 Wisconsin Academy of Sciences, Arts, and Letters. 
in nearly every instance each fold ends or branches before the 
circumference of the intestine is completed. For a distance of 
1mm from its anterior end the mid-intestine is smooth; near 
the middle of the seventh abdominal segment the plicated ap¬ 
pearance ceases, leaving the posterior 2mm, with a smooth ex¬ 
ternal surface. The Malpighian tubules are inserted just be¬ 
hind the middie of the seventh segment. The posterior end 
of the mid-intestine is generally in the seventh segment, a 
few specimens were found in which it was in the extreme an¬ 
terior part of the eighth segment. 
The ileum, the first division of the hind-intestine, extends 
through most of the posterior half of the seventh segment, all 
of the eighth segment and a little into the ninth. On the poste¬ 
rior portion there is the appearance of longitudinal folding. 
In the anterior part of the ninth segment the ileum passes 
into the rectum, this latter section of the alimentary canal 
does not vary in thickness throughout its length. 
The alimentary tract of Libellula 4-maculata passes straight 
through its body excepting a small part of the head; the length 
of the body in a number of speeiments will show slight varia¬ 
tions and a difference in the length of the intestine is also no¬ 
ticed. In measuring some alcoholic specimens it was found 
that the average length of the males was greater than the fe¬ 
males ; ten specimens of each sex were then measured, ex¬ 
clusive of the genital claspers, etc, with the result that the 
average length of the males was 41.65mm, of the females 
39.90mm. The different divisions of the alimentary canal av¬ 
eraged as follows: fore-intestine, male 20.5mm, female 
17.5mm, mid-intestine; male 12.5mm, female 14mm; 
hind-intestine; male 7.7mm, female 6.5mm. The males have 
the longer fore-and hind-intestine, the females the longer mid- 
intestine. The total of the parts of the alimentary tract is 
a little less than the length of the body. The curved portion 
of the oesophagus is slightly less than the distance to the front 
of the head and it is also impossible to accurately measure in 
rough dissections the length of this same curved part. 
