REARINGS AND DISSECTIONS OF TACHINID^. 109 



io ])v swallowed. Ecjually indicative is minuteness, for otherwise the 

 eggs couhl not be SAvallowed entire. It is probable that such eggs, 

 deposited on leaves and intended to be swallowed, remain unchanged 

 without losing their vitality for a very considerable period of time, 

 until they are sw^allowed by the caterpillars. It is equally probable that 

 such eggs are not deposited until the embryo is nearly or quite fully 

 developed, and that the digestive juices and conditions which the 

 egg encounters in the alimentary canal of the caterpillar act upon 

 the chitin and cause the shell to weaken so as to release the maggot. 

 It is certain that such eggs must hatch within a very few hours after 

 being swallowed, othemvise they will pass out with the excrement. 

 One of the fed eggs of Pales painda, above noted, passed through a 

 (lis/xif caterpillar in about four hours. A minute egg can not have a 

 thick chorion and is therefore provided with a chitinized thin one, 

 wdiich withstands atmospheric conditions equally as well as, or better 

 than an unchitinized thick one. Furthermore, the chitinization 

 strengthens the egg and thus lessens the chance of injury to it while 

 being swallowed. Still further, we have found that the chorion 

 of all these eggs possesses a minute raised reticulation, which we con- 

 sider is intended as a framework to strengthen it so as to protect the 

 egg still more fully from injury in being swallowed. Such are the 

 eggs of the Blepharipa scutellata group above described, which in- 

 cludes Pales parhla and Zenillia lihatrix. The chorion reticulation of 

 rhelonia' and other tachinid eggs is not so thickened and raised. 



Enough has been said to show how very largely the reproductive 

 history of the species may be read from the uterine eggs, which can 

 be dissected from almost any female fly, collected or otherwise. It 

 is only necessary that the female be fertilized. Even the ovarian 

 eggs from unfertilized females show a great deal, for we have noted 

 that the ovarian eggs of Parexorisfa ehelonia' show the pedicel while 

 still enclosed within the egg-tubes. 



REPRODUCTIVE CAPACITY OF TACHINID^. 



The capacity for reproduction in the females of the various species 

 of Tachinidae is another very interesting subject, of which surprisingly 

 little is known. The greatest number of eggs that we have noted in 

 the uterus of Pare r arista ehelonia' is about 300, but this number may 

 not represent the full capacity of the females for reproduction. 

 After the uterus is well filled, further eggs may reach it from the 

 ovaries until its extreme limit of distension is finally attained, and 

 still more may follow as the contents are deposited. The uterus 

 of a female of Eupeleteria magnicomis which had begun larviposi- 

 tion was found to contain, at a conservative estimate made from 

 actual count of a portion, 3,200 eggs and maggots. This did not 

 represent the full capacity of the female, for the egg-tubes in the 



