196 THE UNIVERSITY SCIENCE BULLETIN. 
Color. Ventral aspect: White—the abdominal fringe of hairs, the 
ventral abdominal tuft, the hair tufts before the hind coxe and those of 
middle coxe—black. The hairs fringing the hind tarsi are smoky black 
as are the middle and fore tibia. Eyes dark red. No indication of the 
red pigment in the abdomen so conspicuous in older nymphs and adults. 
White with the red eyes—the only conspicuous marking. 
Structural Details. The absence of the median abdominal carina 
from the venter, as is the case also with N. undulata nymphs, is the 
first and most striking peculiarity. The interspace between the eyes is 
large. Beak four-jointed as in adult. Tarsi all one-jointed, terminat- 
ing in two claws. The spiny armature of fore legs is more generalized 
than in later forms. The fringe of the hind legs confined to the margins 
of the tarsi. 
The Older Nymphs. 
In order that space may be conserved, a table of measurements for 
the various instars is presented below and a discussion of the changes 
in structure as development proceeds appended. 
MEASUREMENTS IN MILLIMETERS OF NYMPHS OF B. MARGARITACEA. 
Bopy MEASUREMENTS. Lec MBASUREMENTS. 
INSTAR. Fore Lec. Mippre Lee. Hynp Lex. 
Wad hh)| Sree A S| ies Se ee = 
Lengtn.| Width. | head. oy 5 s : - : 
Femur.) Tibia. | Tarsi. | Femur.| Tibia. | Tarsi. | Femur.| Tibia. | Tarai. 
Ist 1.85 625 5 25 35 20 387 333 275 625 63 625 
2nd 25 702 625 | 3.75 438 313 5 | 438 | 3.75 75 76 81 
3rd. 3.225 938 832 5 62 487 75 625 6 ust ii! 975 
4th. 4.5 1.625 | 1.063 625 75 .563 | 1.063 875 725 | 1.625 | 1.375 1, 287/09 
: 
phen 5.75. 5.3 1.365 8 122 S81 1D p ce 62d aleL gh2amt 2asb 1.85 1.6 4 
Solas ek D2 1.62 1 Bis 1 Vetip lay) 1.25 Dee 2.25 1,95. 4 
of 
6 Pea i.) 2.2 etd it is) Te ae 1.5 se} 5. 2.62 2.3 
* Bueno gives length of species 6.7 to 8.1 mm.; lat., 2.25 mm. | 
; 
The adults of this species are separated in the synoptic table from 
the other two species on the basis of the body length, which is greater 
than 6 mm. This, with a diagnosis of the instars from structural 
characters, may serve to separate the nymphs of this species from those 
of the others. The table of measurements above is based on an average 
of ten specimens of each instar. A larger number would be desirable 
to obtain figures dealing with ratio of growth. The writer believes that 
an examination of a sufficiently large amount of material would show 
for head-widths and limb measurements a ratio of 1:1.25. That is 
to say, the width of the head of the second instar nymph would be ap- 
proximately 1.25 times that of the first instar nymph. : 
Upon attaining the adult stage a sexual dimorphism becomes appar- 
ent. Besides the structural differences of the genitalia, the anterior legs 
