FAMILY PSYLLIDAE 
JUMPING PLANT LICE 
Psyllids are very small, about 2 to 5 mm. long, and look very 
much like miniature cicadas. There is also some resemblance to 
winged aphids, but psyllids differ in having stouter legs, with the 
hind pair fitted for jumping. The nymphs of certain species which 
secrete large quantities of wax resemble woolly aphids. The adults 
are very active and jump or fly when disturbed. 
Hackberry is attractive to many gall-forming species, all of 
which belong to the genus Pachypsylla. Although hackberry 
(Celtis) is cosmopolitan, Pachypsylla is known only in North 
America. Of the five species of hackberry in the United States (C. 
laevigata Willd., C. occidentalis L., C. pallida Torr., C. reticulata 
Torr. and C. tennifolia Nutt.) psyllid galls are recorded for all 
except C. pallida, a spiny bush occurring in the Texas, Arizona, 
and New Mexico deserts. 
Psyllids fall into two species groups, a) the leaf gall makers, 
and b) the woody gall makers. Adults of the leaf feeding forms 
emerge from galls in the fall; the wood feeding forms, in the 
spring. Leaf gall makers are further subdivided into two groups, 
blister galls and nipple galls.’ 
Pachypsylla celtidisvesicula Riley, the blistergall psyllid, forms 
a small, monothalamous (one psyllid per gall) blister gall. It is 
believed to occur throughout the range of Celtis occidentalis in 
the United States and is the most abundant of the hackberry 
psyllids. Fifty or more may infest a single leaf. Adults often be- 
come a household nuisance when thousands accumulate on screens 
in the fall prior to hibernating. Two undescribed species of 
blistergall psyllids occur on C. Laevigata and C. reticulata. 
Pachypsylla celtidisastericus Riley, the hackberry stargall, pro- 
duces a gall which closely resembles the blistergall formed by the 
blistergall psyllid, except it has star-like growth on the lower side 
of the leaf. It can occur on all hackberry tree species except Celtis 
occidentalis. 
The hackerry-nipple-gall maker, Pachypsylla celtidismamma (Ri- 
ley), is perhaps the best known hackberry psyllid. It produces light 
green, nipple-shaped galls on the underside of Celtis occidentalis 
leaves. It is monothalamous, although at times it may appear to be 
polythalamous due to as many as seven galls of P. celtidisvesicula, 
which may be incorporated into a single nipple-gall (537). Like 
the blister-gall psyllid, adults cluster on screens during the fall. 
The nipple-gall psyllid may disfigure leaves when infestations are 
(ae (662). Methods of control are discussed by Thompson 
713) \ 
Pachypsylla celtidisgemma Riley, the budgall psyllid, occurs 
throughout the range of hackberry trees in the United States, and 
may become a pest when populations are high. Adults appear 
during the latter part of June in the New York City area and lay 
their eggs on the young leaves. Young nymphs enter the buds and 
initiate gall formation. The polythalamous galls contain several 
nymphs, each in its own chamber. The winter is passed in the 
fifth nymphal instar in the gali (739). 
“Riemann, J. G. 1961. A study of the hackberry gallmaker genus Pachyp- 
sylla. (Unpublished thesis. Univ. Texas, 201 p., illus.) 
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