622 FIFTH REPORT OF THE ENTOMOLOGICAL COMMISSION. 
rather bright yellow, brownish near center. Average height of gall, 
4 mm j diameter, 3.3""". Cell as in P. c. mamma, the bottom wall at cen- 
ter much Jess thick than at sides. 
P. oeUidisoucurbita var. ?— Gall as seen on the upper side of leaf 
either as in P. c.cucurbita, or more often as in P. c. -globulus, i. e., the 
impression is vertical and widening internally, but the upper rim is 
either barely or not at all elevated. On the under side of the leaf 
it is always sessile, not oval in outline, but depressed and button- 
shaped ; the disk being greatly flattened and with a shallow depression 
having a small central nipple and surrounded by two concentrical rims, 
the inner one often obsolete, the outer one rarely so. The sides of the 
gall have either faint lougitudinal furrows or are irregularly rugose. 
Size very variable ; average height, 1.75 nim ; width, 3""". 
Whether or not this form is specifically distinct from the typical P. 
c.-cucurbita can not yet be decided. Of the latter I have not many 
specimens, all from Missouri; while of the variety I have numerous 
specimens from Missouri and Texas. No specimens strictly inter- 
mediate have yet been fouud. 
Besides the galls just described I possess single specimens which 
apparently represent other species, but their description is postponed 
until more complete material can be obtained. 
The life-history of these Pachypsyllas varies somewhat with the spe- 
cies, but the following summary from my notes gives the essential 
facts : 
Most of the imagos issue in the fall of the year and hibernate in the 
cracks or under the bark of the tree. The sexes pair in early spring, 
and as soon as the young leaves put forth, the eggs are deposited singly 
either on the upper or under sides of the leaf. The young larva settles 
on the upper side of the leaf and inserts its beak in one of the pores. 
The irritation from the puncture causes an abnormal growth of the 
leaf substance, swells around the insect, so that this last appears to 
sink into the leaf and is gradually carried with the growing gall to the 
under side. The gall in all Pachypsyllas is due to the action of the 
young larva, and not to the insertion of the egg. The gall itself soon 
becomes quite perceptible, but the growth of the larva is very slow in 
the early part of the season. After the month of July the larva de- 
velopes more rapidly, and toward the end of September or in October 
the full-grown pupa with its abdominal spines saws an oval or slightly 
crescent-shaped opening through one side of the roof of the gall, issues 
therefrom, and changes to imago immediately afterwards. Many pupae 
remain in the galls and fall to the ground with the leaves, where they 
mostly perish, but some succeed in hibernating and change to imago 
in early spring. 
OTHER HACKBERRY INSECTS. 
Some few other insects occur on Celtis, but they are not important 
and I have so far fouud no time to work at them. 
