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numbers on Nov. 22nd, had all emerged as perfect insects before 

 Dec. 1 2th. The cause of the retardation in development is not 

 clear in this case, but that it may under certain conditions be 

 of an advantage to the species is evident. This would especially 

 be the case in a country subject to long droughts, when vegeta- 

 tion of many kinds is dried up for long periods together, during 

 which the hosts of these parasites must almost cease to exist in 

 a proper stage of development for their attack. It may also bo 

 of use against the attack of hyperparasites, if, as it appears, these 

 have not the same habit of lying dormant, except of course dur- 

 ing winter in cold countries. 



COMPARATIVE STUDY OF GENERIC CHARACTERS 

 OF DRYINIDAE. 



(a). The Mouth-parts. 



The mouth-parts have been largely used in the classification 

 of the Dryinidac by other writers, and they are largely employed 

 in this paper for generic differentiation, as I am convinced of 

 their importance. Obviously the series of genera here consid- 

 ered may be divided into two groups (i) those with short maxil- 

 lary palpi, always less than 6-jointed, and two-jointed labial palpi; 

 (2) those with long or moderately long 6-jointed maxillary palpi, 

 and with three-jointed labial palpi. If however, the number of 

 joints of the palpi in several genera (not accessible to me) as 

 given by Ashmead is correct, then this division will no longer 

 be of the natural character it appears to be, when based on the 

 species and genera herewith described. The only case where it 

 may be necessary to reconsider the generic value of the number 

 of joints in the maxillary palpi is that of Gonatopus (if indeed 

 my species is truly that genus) and Ncogonatopns. Excepting 

 in the number of these joints, G. australiae and N. diibiosiis are 

 practically identical, and might be the same species; but in all 

 other cases, where I have used them to distinguish allied genera, 

 the maxillary palpi are essentially different. The maxillary palpi 

 in the Dryinidac are from two-jointed to six-jointed. In all the 

 genera with narrow elongate stigma to the front wings and with 

 perfectly chelate, long front legs, these palpi consist of a basal 

 part and an apical, distinguished by a natural geniculation at 

 tlieir meeting. The basal part consists of one or two joints; it 

 two-jointed, the first is extremely short and sometimes even 



