462 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
striation of the muscles of the larvce of Phryganids is developed in 
relation with the nuclei ; it is from the nucleus that there grow out the 
striae of the transverse plexuses, on which the refractive granules of the 
developed fibre represent the chromatic bodies of the formative period. 
The author has not been able to make out the origin of the longitudinal 
fibres or of the rods which appear in connection with the granules. 
The transverse plexuses appear first, before the muscle segments, and 
even before the longitudinal fibrils. 
Absence of Wings in the Females of many Lepidoptera.* — Herr L. 
Knatz expresses surprise that biologists have not given more attention 
to the absence or the reduction of wings in many female Lepidoptera. 
There are many grail es of this reduction, from the wingless female 
Psyche to forms like Stilbia and Epimecia, in which the wings of the 
females are but a little smaller than those of their mates. Herr Knatz 
classifies these grades of reduction, and compares them with cases of 
similar sexual dimorphism in Strepsiptera, Telephoridae, and Mutilidae. 
He notes that the distribution alone is enough to show that the 
ancestors of the wingless females must have had wings. This is obvi- 
ously corroborated by the fact that the males are winged, and further 
proof of the reality of the reduction is furnished by the state of the 
rudiments in the pupal stages of the females. External conditions, 
deficient food, warmth, or moisture may injuriously affect the develop- 
ment of wings, or the reduction may be a constitutional variation. 
Females which cannot fly are in some ways at a disadvantage, they 
cannot soar away from their enemies nor attract their mates in flight ; 
but there are obvious compensations, — the sedentary females are often 
hidden, the winged males become proportionately more active and eager 
in seeking their mates, ^tloreover, the reduction of wings is associated 
with a greater development of the abdomen, with an increase in the 
size of the ovaries, with greater fertility. It is therefore hardly sur- 
prising to find that the author is able to give no less than 183 in- 
stances of female Lepidoptera with reduced or absent wings. His 
paper is full of suggestiveness to evolutionists. 
Natural History of Solitary Bees.* — Herr H. Friese records his 
observations on solitary Apidae, describing the two genera of Archiapidae, 
— Prosopis and Sphecodes, twenty genera of Podilegidas which collect 
pollen on their hind legs, and seven genera of Gastrilegidae which have 
either no collecting apparatus or simply a special arrangement of hairs 
ou the abdomen of the females. Notice is taken of the variability of 
these bees, of their seasonal and sexual dimorphism, of their nests and 
stores, of their eggs and larvas, of their modes of life and manner of 
death. Herr Friese also maps out the relationships of the solitary bees, 
basing his scheme mainly on the nature of the collecting apparatus, of 
the mouth-parts, sts. But the importan f lus c 
tion consists in the numerous observations which he has made on the 
natural history of the twenty-nine genera described. 
* Arch. f. Xaturgcseh., lvii. (1S91) pp. 49-74 (1 pi.). 
t Zool. Jahrb., v. (1891) pp. 751-860 (1 pi.). 
