. Bulletin of the Department of Agriculture. Agriculture. When she has made her selection of a suitable stem, the female usually alights about half way up and runs briskly to the upper end, halting almost imperceptibly every few steps. The gait of an ascend- ing fly is so characteristic that it determines with much certainty if the individual is a female intent on oviposition. Arriving at the apex of the stem, after a care- ful survey of its condition, she frequently makes an elaborate toilet, preening herself most care- fully, until she is in perfect condition. She then descends, exagger
. Bulletin of the Department of Agriculture. Agriculture. When she has made her selection of a suitable stem, the female usually alights about half way up and runs briskly to the upper end, halting almost imperceptibly every few steps. The gait of an ascend- ing fly is so characteristic that it determines with much certainty if the individual is a female intent on oviposition. Arriving at the apex of the stem, after a care- ful survey of its condition, she frequently makes an elaborate toilet, preening herself most care- fully, until she is in perfect condition. She then descends, exaggerating slightly the hesitating step by which she had ascended. The antennae are held horizontally in front of the head as she moves, and she occasionally touches the surface of the stem with their tips. There is none of the rapid anten- nal vibration so common among the smaller chalcids and many other Hymenop- tera. She gives no evidence of being in search of any particular point, but goes straight down the stem. When satisfied that she has gone far enough she halts abruptly, usually an inch or less above the second node from the top of the stem, slowly arches her abdomen and clasping her hind pair of feet around the stem as far as they will reach begins to drive the saws into the hard outer tissue. Figure 13 shows the attitude taken at this time. These saws are exquisitely fashioned, curved like a scimitar, double, very thin with serrated edges. (See fig. 14.) They are used to split the outer coating of the stem rather than to cut it, and they make an opening so exceedingly small that it is almost impossible to find the scar after the wound has healed. These saws are gradually" forced into the stem, the operation occupying a minute or more. In the field the female always heads downward during oviposition and the curve of the saw blades brings them, when fully inserted, in a line parallel to the axis of the stem. They are frequently partly withdrawn and then direction sligh
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