164 BULLETIN OF WISCONSIN NATURAL HISTORY SOCIETY. VOL. 3, NO. 4. 
the life of the average bee-larva. It is hardly necessary to state 
that the presence of such a larva in the cell of a leaf-cutter bee 
means certain death to the rightful owner. 
TRIEPEOLUS HELIANTHI ROB., A PARASITE OF MELISSODES 
TRINODIS ROB. 
Melissodes trinodis, a ground inhabiting bee digs down per- 
pendicularly to a depth of about 8 cm., then turns off obliquely 
for a short distance, and continues in a perpendicular direction. 
The cells are somewhat thimble-shaped, their walls are formed of 
hardened clay with a very smooth and polished inner surface. 
They are filled about one-half with bee-bread. 
The visit of the parasite Triepeolus helianthi to a nest of 
Melissodes trinodis on August 17, 1903 led me to open the nest 
on the day following. Two cells were exposed, one unfinished, 
the other closed, and showing the white, opaque egg of the host, 
3mm. in length on the surface of the bee-bread. Nothing else 
was observed on this date. My further notes are as follows: 
August 20, 8 P. M. The Melissodes-egg seems to be near the 
point of hatching. 
August 21, 6 A. M. The recently hatched host-larva is dead, 
and has evidently been killed by a para- 
site. Close to it on the bee-bread is the 
dead body of a parasitic larva with long 
curved mandibles (Triepeolus helianthi). 
Crawling lively around the smooth wall 
of the cell, above the bee-bread another 
larva of Triepeolus is observed, making 
biting movements. After a while this 
larva crawls down to the bee-bread, and 
bites the body of the dead parasite a few 
times in succession. Later on the sharp 
mandibles of a third parasite appear from 
below the surface of the bee-bread, also 
making biting movements. 
8 A. M. Only one parasite alive, crawling around 
the wall. On the bee-bread the dead 
bodies of the two other parasites, as also 
of the host-larva. Any interference with 
the cell causes the parasite to open and 
close its mandibles several times. This 
larva has a number of flat lateral appen- 
dages (Fig. 7), organs of locomotion that 
