12 FIFTH REPORT OF THE ENTOMOLOGICAL COMMISSION. 
proved in an extensive and beautifully illustrated memoir* the fact 
of alternation of generations in a number of European species. 
In a notice of Adler's work in the American Naturalist for July, 
1881, Professor Riley added that Mr. H. F. Bassett "has, following 
Adler's interestiug experiments in Europe, suggested the probable di- 
morphic, connection of several of our vernal galls which produce bisexual 
individuals, with autumnal forms which produce larger asexual flies. 
Dr. Adler gives a list of nineteen species of Cynipidre in which the oc- 
currence of dimorphic forms has been proved, giving the names of 
the agamic forms and the corresponding bisexual forms the latter 
of which, in all cases, were referred to distinct genera by previous ob- 
servers. 
In this connection should be mentioned the remarkable fact that in 
certain closely allied species (Aphilotrix seminationis, marginalis, quad- 
rilineatus and albopunctatus) no alternation of generations seems to 
occur. 
Saiv-flies. — These often seriously injure evergreen trees, while they 
occur on all other trees. There are a large number of species. Their 
larva3 resemble caterpillars in appearance and in voracity. The flies dif- 
fer from wasps, etc., in the abdomen being broad at the base j the body 
is somewhat flattened, and the head is wide, while the antennas are not 
elbowed, and as in Lophyrus are pectinated in the males, serrated in the 
females. In the end of the hind body of the female is situated the 
u saw" or ovipositor. This consists of two blades, the lower edge of 
the lower one of which is toothed like a saw, and fits in a groove in the 
under side of the upper blade; both blades being protected by sheath- 
6 s 
Fig. 1.— Saw of a saw-fly (Hylotoma): a, lateral scale; i, saw; /, gorget. After Lacaze-Duthiers. 
like stylets. On pressing the end of the abdomen the saw is depressed ; 
by this movement the saw, which both cuts and pierces, makes a gash 
in the soft part of the leaf, where it deposits its eggs. (Fig. 1.) 
The Lophyrns of the pine makes a series of punctures on each side of 
a pine needle ; the Nematus of the alder makes from twenty to forty pairs 
of semicircular punctures in the under side of the midrib of the leaf, 
while the larch saw-fly inserts her eggs in two alternating rows at the 
*Zeitschrift fur Wissenschaftliche Zoologie, xxxv, Feb. 1, 1881, pp. i:>l-'24b\ Pis. 
x— xii. Dr. Adler's researches were commenced in 1875, and his first paper appeared 
in 1877. (Deutsche Entomolog. Zeitschrift, 1877, Heft 1.) 
