240 
gill located near each side of outer 
basal angle of submentum...Perlodidae 
(Perlodes, Isogenus and Hydroperla) 
Without such gill on submentum....... 2 
9, Lateral margins of forewing pads ap- 
proximately straight or in line with 
longitudinal body axis; tip of lacinia 
with one or more teeth; diameter of 
fourth segment of maxillary palpus 
not much greater than base of fifth 
segment; nymphs frequently with a 
conspicuous color pattern on dorsum 
Of Mabd omen veneer, eee ae eee in eee 10 
Lateral margins of forewing pads round- 
ed; tip of lacinia never with more 
than one tooth; diameter of fourth 
segment of maxillary palpus often 
much greater than base of fifth seg- 
ment; nymph without conspicuous 
color pattern on dorsum of abdomen 
(sometimes color pattern of adult 
ready to emerge is evident through 
ny wp halesskin eae Chloroperlidae 
10. Maxillae bulging out from sides of head 
in a very conspicuous manner; diame- 
ter of lacinia from base to apex tapers 
very rapidly, and it forms a_ long 
single claw or a long claw plus a 
secondary one; color pattern of ab- 
dominal tergites suffused or with dis- 
tinct transverse markings........... 
CAPER Nit ha, Be Perlodidae (Diploperla)* 
Maxillae not or but slightly bulging out 
from sides of head; diameter of la- 
cinia from base to apex less tapering, 
structure in general of more stocky 
form with smaller teeth or tooth at 
apex; color pattern of abdominal ter- 
gites suffused or with distinct longi- 
tudinal seinalkin gs een near Isoperlidae 
Revised List of Illinois Species 
The number of species of stoneflies now 
known to be found in Illinois represents a 
great increase over the numbers in all for- 
mer lists. In briefly reviewing the growth 
of the Illinois faunal list it will suffice to 
quote from my papers of 1935a and 1937. 
In 1935 I wrote: “A revised tabulation 
of the species recorded by Walsh from the 
vicinity of Rock Island in 1862 gives us 
a present list of 15 species. In the tabu- 
lation of species by states as given by 
Needham and Claassen (1925), L[linois 
is credited with 14 species, but since two 
species of Pteronarcys are listed ‘whereas 
all our evidence indicates but one, this 
list of 1925 includes only 13 species. If 
all the Walsh records had been placed by 
Needham and Claassen their list would 
have given 17 species for this state. Our 
studies to date give us a total of 36 species 
of stoneflies for Illinois plus at least two 
*Nymph of Dictyopterygella when found will probably 
key out at this place. 
ItLIno1s NATURAL History SURVEY BULLETIN 
Vol. 22, Art 
and possibly a third species as yet known 
only as nymphs and not placeable to species 
at the present time—a list more than 
double those of Walsh or Needham and 
Claassen. 
“The status of two Acroneuria nymphs 
and another nymph which I am tentatively 
placing as Neophasganophora needs to be 
definitely established. “Two of these, one 
Acroneuria and the Neophasganophora, 
are certainly species which are additions 
to our list. “he second Acroneuria nymph 
now unnamed may represent a light phase 
of a species already reared and known, but 
there is also a possibility that it may be 
new to our list.” 
In 1937 I wrote: ‘These specific place- 
ments [assignment of specific names, based 
upon rearings, to two species known only 
from unidentifiable nymphs in 1935a] 
bring the total of Illinois stoneflies to 38, 
with the certainty that two additional 
species will be added by future studies, 
one a questionable identification of a fe- 
male Capnia as vernalis Newport and the 
other an Isoperla represented as yet by a 
single nymph not placeable to species.” 
The rearing and collecting of Illinois 
material since 1937, together with the 
rearing and collecting of material from 
other states, have now expanded the IlIli- 
nois faunal list to 49 species, which is 
greater than the number recorded for any 
other state except New York. The New 
York list of 1928 contained 59 recorded 
species, but at least two of these names 
are involved in the synonymy of other 
listed names. Additional species have been 
collected in New York since then, and the 
final list has possibilities of some 60 species. 
The Illinois list may eventually be aug- 
mented by a few additional species, but 
our field work has been so comprehensive 
that but few species can possibly be added. 
No Illinois nymphs are now known which 
cannot be placed to species. Of species 
known to occur in adjacent states, A cro- 
neuria areta, Isoperla dicala and Tsoperla 
namata, all described in this paper, may 
sometime be taken in Illinois. 4 croneuric 
areta is found in the Ohio River basin 
and specimens are a possibility at point: 
along the boundary waters of the Ohic 
River in southern Illinois. [soperla nama 
ta has been taken in two states, Indiané 
and Missouri, adjacent to southern Illinot 
and thus may eventually be found withir 
