5°2 
Saw-flies, Gall-flies, Ichneumons, 
they are familiar with the details of the landscape in the district they inhabit. 
Fair eyesight and a moderately good memory on their part are all that need 
be assumed in this simple explanation of the problem.” 
In the last of Sharp’s divisions, on the basis of habit, are those solitary 
wasps that make nest-tunnels in wood or the stems of plants. In the pith 
of various kinds of cane-bearing plants, as brambles, blackberries, etc., 
may often be found the tunnels (Fig. 707), provisioned with plant-lice or 
other small homopterous bugs, of various small 
wasps of the families Mimesidae and Pemphredo- 
nidae. The Mimesids have a petioled abdomen 
and look like little Sphecids; the Pemphredonids 
are shining black. The family Crabronidae, a 
rather large group of solitary wasps distinguished 
by having only one closed submarginal cell in 
the fore wings, includes many wood-borers. Very 
common in sumac-branches, according to Com¬ 
stock, are the nests of slender yellow-banded Tri- 
poxylon jrigidum; the cells are separated by mud 
partitions. The Peckhams found two slender- 
waisted, black species of Tripoxylon common near 
Milwaukee, namely, T. albopilosum, } inch long, 
with tufts of snowy-white hairs on the fore legs, 
and T. rubrocinctum, a little smaller and with a red 
band about the body. Although these wasps are 
normally wood-borers, they will use convenient 
cavities in any material; rubrocinctum was found 
using crevices in the mortar of a brick house, 
and the straw of a stack where thousands of 
the cut ends of the straws offered attractive 
clean nesting-holes; albopilosum was found nest- 
Fig. 707.— Nest-tunnels of ing in holes made by beetles in posts and trees, 
x yP carpenter-wasps. A, p ut never j n straws; a third common species, 
nidge) ; B, Stigmus jratemes bidentatum , seemed to nest only in burrows tun- 
(After n eled by itself in the stems of plants. Another 
carpenter-wasp, common in the eastern states, 
is the large Eumenid species, Monobia quadridens , which drills a tunnel in solid 
wood, dividing it into cells by transverse partitions (Fig. 707 ,A). The species 
of the genus Crabro make their nests especially in the canes of blackberry- 
and raspberry-bushes. The Peckhams found that Crabro stirpicola did 
much of its work at night, something not observed in the case of any other 
solitary wasp. This species provisioned its cells with various species of 
flies. 
(Pemphredonidse). 
Comstock; natural size.) 
