402 
l^riefe. 
mit weissem Blütenstaub gefüllt, in welchem, wie in einem Mehlfasse, die $ der 
Blastophaga oder Ichneumoiden herumkrabbeln. Auffallend ist hier, dass Blasto- 
phaga im Vergleich zu den Tchneumoniden sehr selten ist; in manchen Feigen, 
wo es von letzteren wimmelt, habe ich von ersteren gar keine gefunden. — Ich 
schicke Dir ? und J der beiden Arten. — Neugierig bin ich, ob jede unserer 
ziemlich zahlreichen Ficus-arten ihre eigenen Befruchter hat; wahrscheinlich ist 
es mir, da, wenn dieselbe Art von Insecten die verschiedenen Feigen besuchte, 
häufig der Blütenstaub auf fremde Arten getragen werden würde 
An Dr. Ernst Krause, Berlin. 
Blumenau, 14. December 1880. 
Von dem Kosmos-aufsatz über Paltostoma hat Osten-Sacken im 
Novemberheft des Entomolog. Monthly Magazine kurze Mittheilung gemacht; es 
scheint ihm schwer zu werden, an den Dimorphismus der Weibchen zu glauben, 
und ich habe deshalb eben einen kurzen Artikel darüber für das Monthly Mag. 
geschrieben ^) 
On female dimorphism of Paltostoma torrentium. 
By Dr. Fritz Müller^). 
As there seems to be some hesitation in accepting the female dimorphism 
of Paltostoma torrentium (see Ent. Mo. Mag. XVII p. 130) I will here very briefly 
State the facts which seem to me to prove that the two sets of females belong 
to the same species. 
First as to the sex of the three forms of Paltostoma. Were it not for Baron 
Osten-Sacken saying that "error may easily occur", I should have thought it 
quite unnecessary explicitly to State, that I ascertained the sex by examining 
the internal sexual organs; the females of either sex have three dark brown pear- 
shaped receptacula seminis; the eggs, in nearh' ripe pupae, are 0.5 mm. long, 
0.13 mm. thick, one side beeing more convex and one end a little more obtuse 
than the other. 
Had the males and the two sets of females been caught at the same locality. 
it would indeed have been rash to consider the females (videly differing in the 
Organs of the mouth, the size of the eyes, atid the structure of the last tarsal 
joints) as belonging to the same species. But the case is quite different. In the 
rapids of some of our rivulets the larvae and pupae of Paltostoma are extremely 
frequent, and may be collected in large numbers. Thus I have been able carefuUy 
to compare and to dissect hundreds of them ; but I have not discovered any 
differences corresponding to the three sets of flies. From the pupae I have 
extracted repeatedly numerous flies, and have always met with two sets of 
females, and never with more than one set of males. The two sexes seem to 
occur in about equal numbers. One day from 70 pupae I extracted 20 males and 
1) Dieser Aufsatz hätte in die Ges. Schriften aufgenommen werden sollen, ist aber übersehen worden 
und folgt deshalb hier im Anschluss an den Brief an Emst Krause. 
2) The Entomologist's Monthly Magazine, Vol. XVII, London 1880— 8l, p. 225. 
