FIELD BOOK OF INSECTS. 



days. I have kept unmated adults alive, under the same 

 conditions, for about three months. A bit of banana in a 

 milk bottle is all the apparatus one needs to breed this 

 creature and twenty generations a year are easily reared. 

 These facts and its other virtues make it an ideal labora- 

 tory animal. Not only have simple cases of Mendelian 

 inheritance been conveniently studied but more complex 

 ones and also the relations between body-characteristics, 

 including sex, and the chromosomes in the germ-cells 

 have been analyzed by its aid. The adults are perfect 

 slaves to light (heliotropic). Put a number of them in a 

 bottle and they will all crowd to the part which is nearest 

 the window, no matter how much you may turn the bottle 

 about. The males are a trifle smaller than the females 

 and have the hind part of the abdomen more largely 

 pigmented. The males have relatively immense "sex 

 combs" on their front legs. These may be for the sake of 

 appearing more attractive to the females, as the males go 

 through their courtship dance, but, on numerous occasions, 

 I cut them off without thereby noticeably decreasing the 

 success cf the combless males in the rivalry, which I then 

 staged, with normal males. The "sex combs" may be 

 to clean his antennas, but how does she keep hers clean? 

 They may just happen to be. 



In this brief review of the Acalypterates the following, 

 among other, families have been skipped. HETERONEURI- 

 D^E: the larvae live in decaying wood, etc., and "skip" 

 like Piophila. SEPSID;E: Piopliila has been put here; 

 they often swarm about the decaying vegetables and excre- 

 ment in which their larva? live. DIOPSID^E : our only species 

 is Sphyracephala brevicornis, which occurs on skunk- 

 cabbage and may be recognized by its eyes being on stalks. 

 EPHYDRID/E: these small or even minute flies are usually 

 found about moist places; the aquatic larvae of some 

 species have "rat-tails " like Eristalis but the tail is forked; 

 some larvae live in salt or alkaline water, others in the sap 

 of trees and in leaves. AGROMYZID^E: numerous small 

 flies; some larvae are leaf-miners, others live in plant-galls; 

 others feed on plant-lice, creeping like leeches or Geometrid 

 larvae. 



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