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Sceliphron maderospatanum (Fabricus). 
Length 18 mm.; black; yellow on thorax, legs and pedicel. 
One of these common little lowland wasps built her mud cells 
in the College insectary, plastering them on the under surface 
of the metal lid of a jelly tumbler, said lid being jammed into 
another so that the undersides faced each other and presented 
a wide gape to one side. She was an exceedingly tame insect, 
and I could pick up the lids, gently separate them and minutely 
examine her at work. Sixteen days were required to complete 
her 9-cell nest, whose rather thin-walled cylindrical cells she ar- 
ranged in two rows, and as they were stored, she plugged them 
and plastered over the space between them with mud. Although 
a swift worker, she did not keep regular hours, nor fill one cell as 
quickly as another—weather and material regulated her activities 
to a certain degree. Being in plain view from the insectary table, 
at which I spent a good deal of time, I was able to keep pretty 
good tab on her operations. She did not sleep in the vicinity of 
her cells, but would arrive at her nest not earlier than 7:30 a. m., 
sometimes as late as 9, and once at 10:20 a. m.; and on the next 
to last day I did not see her at all. Her day’s work was com- 
pleted at a comparatively early hour, often at 3:30 p. m., though 
she would sometimes be seen much later, but not at work. She 
could build a cell in from half to three-quarters of an hour; the 
mud is brought in her mandibles and probably other mouthparts 
supporting, and applied to the desired spot and drawn with a 
series of biting or munching motions, first downwards and then 
upwards, the forefeet on either side appearing to support some- 
what the fresh mud. The cell complete, the next step was to 
fill it with numerous, rather long-legged spiders of divers kinds ; 
these were captured outside the insectary, the wasp flying with 
one to near her nest and performing the rest of the journey on 
four feet, the front pair of legs and her jaws holding the victim 
closely to her chest. The egg is laid on the first spider intro- 
duced. The wasp, after examining this spider, backs out of the 
cell, turns about and then backs in and lays the egg; this is shin- 
ing yellowish white, of nearly uniform thickness, slightly curved, 
and about 3.10 mm. long by 0.85 mm. wide. 
It usually happens that she is unable to completely store a 
cell in one day. Leaving her victims in an open receptacle 
exposed to the attack of ants is not to be thought of, so the cell 
is temporarily closed for the night with a thin concave disc of 
mud very different from the stout and permanent plug used when 
storing is complete. One load of mud with a few bites of dried 
clay from the cell itself is sufficient material for this disc. It is 
