Article beginning on page 197.
Psyche 9:197-198, 1900.

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and shapcs that side into the form and or less of preparation, the butterfly is protection of a cell. once more upon the wing- a stranded The chrysalis state is assumed in relic of the great Ice Age, like the alpine June, and lasts two weeks or more, sandwort, Arenaria groe?zIandica, whose and then again, after two years more honeyed sweets it now robs. VARIATION IN TRIDACTYLUS.
BY A. P. MORSE, WELLESLEV, MASS.
7?id(tcty//~s is a genus of small, fosso- rial crickets, allied in structure and hab- its to Grylhtalpa, the mole-cricket, and differing most noticeably from that genus, among several things, in being smaller
in size and possessing remarkable salta- tory powers.
Representatives of the genus occur
over the greater part, at least, of the
'United States, and range in size from
six to twelve millimeters in length when adult. They frequent the margins of
streams and ponds, burrowing in the
sandy loam of the banks and shores,
and may be secured, when a station is
discovered, by sweeping rapidly just
above the ground with a net of cheese-
cloth or other close-meshed material.
Owing to their alertness, activity, and
leaping mode of progression close obser- vations of their habits are exceedingly
difficult to make out-of-doors and but
little is known regarding them. Whether
confinement would secure satisfactory
results remains to be learned, but it is hoped that some one having an oppor-
tunity to do so will make the attempt
and if possible discover the special func- tion of the remarkably modified anterior tibiae of the male in certain species and the significance of the variation noted
below.
While collecting on Nantucket Island
late in the afternoon of July 12, 1900, I found a locality for Tridactylus on the
shore of a small pond and captured
several examples of both sexes. On the
foliowing day additional specimens were
secured in the same place and about an
adjoining pond. On my return home,
examination after mounting disclosed an
interesting state of affairs.
The 52 specimens taken on the two
successive days in this one locality con- sist of one immature, 18 females, and
33 males. These exhibit no essential
difference in color, size or markings
leading one to infer the presence of two species, nor do the female examples dif- fer in structural details. A close exam- ination of the males, however, reveals a singular variation in the structure of the anterior tibiae. In about one third of
the males the form is the same as that
of the female (Fig. I), - more or less
irregularly ovate in outline, terminating



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198 PS YCHE. [ ~ a .
distally in four prominent, equidistant
teeth, with the convex posterior face
thickly set with hairs and a row of
stouter hairs or spinules on the outer
margin, the tarsus being inserted be-
tween the first and second teeth and
lying on the anterior face. In three of
the others, while the structure remains
similar, the outline of the tibia has
become subtriangular through the pro-
duction of the inner side of the distal
7"ridmty?~a tw:ni~Zi~ Scucld. Left autcrior leg !,icwed from behind. Fie. 1. Female. Fig. a. Male. Fig. 'å´{ Male Fig. 4. Male. fig. 5. Male ; tibia closed upon the fen,,,r.
end (Fig. 2); in addition to this, there is a slight but distinct deepening of the fissure between the second and third
teeth. This lengthening of tt'hat may
be called the inner limb of the tibia and deepening of the emargination between
the inner and outer limbs is exhibitt
all the remaining specimens in pro
sive degree until we have a remari
bifurcate organ (Figs. 4, 5) whose
tion to the normal form would be I
out with difficulty but for the seri
connecting gradations.
In addition to this bifurcation an
elongation of the inncr limb, the
loses its hail-y covering, the inner
tooth nearly disappears, the secoi
greatly prolonged into a backw
directed claw-like organ, the third
fourth teeth (on the outer limb) be
enlarged and produced, the anglf
tween the two limbs becomes gr
and greater, and the femur acq
tooth-like protuberances on its prox
inncr, ventral angle and becomes 5
ly enlarged (trig's. 1-5). The grad
is so perfect (even in this relat
small series of examples) that it i!
possiblc to draw any sharp line o
marcation between the specimens ; :
times, even, the right and left tibi:
the same insect are appreciably diff
in form. Of the 33 males, in tel
tibia is of normal ( 9 j form ; in
others it is slightly but perceptibly I
lied, in one it is intermediate bet
Fig. r and Fig. 2, in two it is of the
of Fig. 2, in two intermediate bet
Fig. 2 and Fig. 3, in four like Fig.
one midway between Fig. 3 and F
in four but little less modified th;
Fig. 4, and in six it has the form of
4 (open) and Fig. 5 (closed), the gr
elongated second tooth varying mu




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May, i9o11 PSYCHE. 199
curvature (foreshortened in Fig. 4).
Each of the extremes of the series is
thus represented by about one third of
the specimens, and the intergrades by
the remaining third, but these intcr-
grades are so numerous and the grada-
tion is so perfect that it is quite impossi- ble to separate the specimens into two
series. Nor is there reason on other
grounds for so doing. The specimens
evidently all belong to one species ex-
hibiting a high degree of secondary
sexual variation in the male, a variation whose function and value have yet to be
determined, but the key to which may
perhaps bc secured by careful observa-
tion of the habits of the species.
This character-the form of the ante-
rior tibiac of the male-has been used for many years in systematic treatises for
distinguishing the species of this genus but it is now evident that its worth has been greatly over-rated and it must be
regarded with suspicion and in some
cases as worthless for that purpose.
In certain forms, of which I have ex-
amined considerable series, this great
variability apparently does not occur,
the tibiac of the male and female being, alike. The extremely bifurcate condi-
tion was recorded and figured by Mr.
Scudder in characterizing T, apicalis Say and T. termhidis Scudd. (Boston Journ.
Nat. Hist., vii, p. 424,-1862). The form I have treated above is the latter of
thesc-temhalis. and from material in
Mr. Scudder's collection I am able to
slate that at least the normal ( 9 ) form of tibia is found in males of @ic& also.
Possibly te.r'}u/naZis may prove to be but a race of apicalis but until the genus is revised it is best to regard them as differ- ent, apiciifis appearing slightly larger, paler in color, and usually having rela- tively longer wings. Both of these forms are widely spread over at least the east- ern half of the States, and are
apparently not unccxnmoii locally. It is hoped that anyone having an opportunity
to do so will make observations on the
habits of these interesting little crickets and attempt to discover the use of this
peculiar modification of the tibiae and
its value to the insect.
PULVINARIA INNUMERABILIS RATHV
BY GEO. B. KIHG, LAWRENCE, MASS.
Although %.!~/i7lariil innuuieratilis evident to the writer, that a more clear Rathv. has been the subject of many and comprehensive description should published articles, together with illustra- be given together with some descriptive tions of the species in its various stages notes of its variation and distribution ; of developments; it has become quite moreover it is hoped that the following



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