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nally side by side, devour the food supply of the host, grow 
rapidly and spin their cocoons before the host-larva has reached 
one-fourth of its size. According to Fabre's opinion the latter 
dies of starvation, but he has not been able to verify this by ob- 
servation. In some cases he has found the dry remains of the 
mason-bee among- the cocoons of the guest-bee, but he has just 
as frequently discovered nothing whatever of the mason-bee 
larva. There is another guest-bee Dioxys clncta that lays its eggs 
in the nest of Chalicodoma. Fabre, (4), has repeatedly encount- 
ered either the larva or the imago of Dioxys in the nest of the 
mason-bee, but never the slightest trace of the latter in the same 
cell. Verhoeff, (5), seems to be the only one who so far has 
witnessed, and described the attack of a parasitic guest-bee on 
the larva of a host-bee. The parasite in this case is Stelis mirmta 
Nyl., inhabiting the nest of Osmia leueomelama Kirby. The 
host-bee constructs her nest in dry blackberry stems by ex- 
cavating the pith, and forming a tunnel in which a row 
of cells is placed, one above the other. Each cell is partly 
filled with the mixture of honey and pollen usually called "bee- 
bread," and is separated from the adjoining one by a partition 
made of pieces of green leaves chewed by the bee, so as to form 
a soft pliable mass. Verhoeff emphasizes the following points. 
1. Stelis minuta deposits its egg earlier than the host-bee, and 
in the lower region of the bee-bread. 2. The larva of the 
parasite hatches a little earlier than that of the host-bee, whose 
egg is situated on top of the bee-bread. 3. Both larvae, which 
at the beginning are of about the same size partake of the bee- 
bread, the host-larva on top, the parasite below. 4. The latter 
gradually increases in size, and consequently advances towards 
the host-larva on top. 5. Finally the parasite, which in the 
meanwhile has become twice as large as the host-larva comes in 
contact with the latter, kills it, and eats it. Verhoeff informs us 
that there was a mutual exchange of hostilities between the two 
larvae, each trying to grab the other with its mandibles, but that 
finally the parasite succeeded in burying its mandibles in the 
head of the host-larva. The latter was eaten up within 1 or 2 
days. This account given by Verhoeff has been considered 
somewhat in detail for the purpose of comparing his results with 
those obtained by me from observations made on Stelis sexmaeu- 
2. T). Sharp. The Cambridge Natural History, Vol. f>, p. 59. 
3. J. IT. Fabre. Souvenirs Entomologiqnes, Vol. 3. p. 114. 
