METHODS OF COLLECTING AND PRESERVING DROSOPHILIN®. 45 
D. simulans, D. funebris, D. obscura, D. affinis, and D. cardini this 
difference is quite well marked. 
Size: In most species the males average a little smaller than the 
females. In the case of D. melanogaster this size difference is a true 
secondary sexual character, as has been shown by an examination of a 
large series of gynandromorphs (Morgan and Bridges, 1919). In these 
specimens male and female parts are combined in the same individual; 
and it is regularly observed that the male parts are a trifle smaller and 
bear somewhat smaller bristles and hairs. I have observed the same 
relation in gynandromorphs of D. simulans. 
Abdominal structure: As has been pointed out above, the abdominal 
structure of the two sexes is different in the genus Drosophila. The 
female has seven well-developed dorso-lateral plates, the male only 
five. The spiracles are correspondingly different—the female has 
one on the fifth segment and one on the sixth, while the male has two 
on the fifth. The ventral abdominal plates are also different. The 
female has six, the male four, and the posterior members of the series 
are quite different in shape in the two cases. 
IX. METHODS OF COLLECTING AND PRESERVING 
DROSOPHILINAE. 
Most of the Drosophilinz feed on fruit or on fungi, or have leaf- 
mining larve. The most efficient places to collect them are where food 
is plentiful. Fruit in grocery stores will yield the commoner species, 
and more especially the widely distributed ones that are presumably 
introduced. Windfall apples or other decaying fruit usually repays 
examination. ‘Tomato patches, even before the fruit is ripe, are 
worth sweeping. Garbage piles usually have many species. Fleshy 
fungi, either agarics or Boletine, will yield many forms; they are 
more prolific after they have decayed somewhat. Bleeding trees should 
always be examined. 
My own practice has been to expose fruit in the woods, and collect 
from it daily for a while. The fruit is usually placed in a bottle and 
hung in a low tree. This method makes it less likely to be stolen by 
small mammals, and makes collecting easy, as one simply pours the 
flies into his collecting bottle. After a week or so the bottle may be 
brought in, and the larve and pup2 allowed to develop, thus increasing 
the collection. For this kind of collecting it is advisable to use many 
different sorts of fruit. I have found banana, pineapple, tomato, and 
peach to be specially satisfactory. 
I always bring the collections into the laboratory alive, in order to 
be able to breed any forms that seem desirable. If this is to be done 
it is necessary to be careful, especially in the case of sweepings, not 
to leave predacious forms (spiders, empidids, asilids, ants, etc.) or large 
