1932 ] 
A Wireworm Double Monster 
39 
habits makes observation rare indeed. For these reasons it 
was decided to report this case. In order to insure that 
this partial twin should not be lost it was killed and fixed 
as soon as discovered and, as a consequence, growth records 
were not obtained. It is hoped that another individual 
will be found so that developmental changes can be noted. 
The specific type of anomaly possessed by the individual 
here reported is classified by Cappe de Baillon 2 as a sym- 
metrical double monster with lateral abdominal doubling. 
This particular diplopagisity, according to Wilder 3 , is be- 
lieved to be due to wide separation of some of the segmen- 
tation nuclei in early embryonic development, perhaps be- 
ing traceable to the two-cell stage. Had there been com- 
plete wide separation there would have been identical twins. 
In phasmid larvse Cappe de Baillon found that abdominal 
doubling was very rare as compared to cephalic or thoracic 
doubling. In fact very few larval irregularities of any 
type have been reported. In adults abdominal monstrosi- 
ties are very rare as compared with other types. This 
fact is strikingly noticed when the literature of reported 
cases is reviewed. 
This particular larva has a perfectly formed head and 
thorax as well as the first five abdominal segments as far 
as external study indicates. The sixth segment is irregu- 
lar in shape, being double at the bottom but single at the 
top. The last three segments are apparently normal but 
duplicated. The digestive tract appears to be double 
throughout the sixth segment and divides at the junction 
of the fifth and sixth segments, the irregularity beginning 
about the middle of the fifth. The fat bodies, the only other 
internal structures visible, seem to conform to the external 
arrangement. The length of the larva is the same as the 
rest of the worms from the same mating if either of the 
tails are used. The volume would be the same if the dup- 
licated parts were removed and the sixth segment trimmed 
to normal shape. There does not seem to be any atrophy 
or hypertrophy except as noted above and each duplicated 
segment is like the corresponding somite of the other half 
