THE DOCK FALSE-WORM. 33 



While no rule can be formulated from the foregoing table/it will be 

 noted that the amount of increase in temperature required to reduce 

 the pupal period one day was greater as the pupal period grew shorter. 

 It required an increase of 3.31° to reduce the pupal period from 14 

 days to nine days, a reduction of five days, while in order to reduce 

 it from nine days to four days, a further reduction of five days, an 

 increase in temperature of 11.98° was necessary, or over three times 

 as much. The reason for this is evident. It must be remembered 

 that during the pupal stage important changes are taking place. 

 The relatively simple larva is being transformed into the highly com- 

 plex adult insect. These changes require a certain minimum amount 

 of time, in this case apparently three or four days. On the other 

 hand, there is, at least theoretically, no limit to the maximum amount 

 of time during which the insect may remain in the pupal condition. 

 Hence, as we approach the minimum a greater increase in tempera- 

 ture is necessary in order to produce a given reduction in the length 

 of the pupal period. 



NATURAL ENEMIES. 



HYMENOPTEROUS PARASITES. 



ICHNEUMONIDS. 



The overwintering material of the dock false-worm, colleoted in 

 March, 1915, proved to be rather heavily parasitized. Accordingly 

 a careful record was kept of the parasites, and some knowledge of 

 their life histories was obtained. The parasites emerging were all 

 ichneumonids, and belong to seven distinct species. Mr. R. A. 

 Cushman has examined these and finds them to be Epiurus ptero- 

 phorae Ashm., Hp'docryptus sp., Aenoplex sp., Bathymetis sp., Bathy- 

 thrix sp., and two species of Cratocryptus. As only three species were 

 recognized at the time of rearing, and the data obtained were rather 

 meager, they are not presented here. It is certain, moreover, that 

 some of these species are secondary parasites. It is hoped that the 

 opportunity will be presented for further investigations in order to 

 work out this problem. 



The adults of all these ichneumonid parasites emerge through a 

 hole, bored opposite the pupal cell and not through the entrance hole 

 of the false-worm. They are nil more, active than the adult sawfly. 

 They are all similar in appearance, and not unlike the adult sawflies, 

 being slender and black, with reddish legs. The antennae are longer, 

 however, the abdomen more slender, and I he ovipositor of the female 

 i eonspicuou . The adults of Spilocryptus ii.ro further distingushed 



by a reddish hand aCTOSS the anterior half or two-thirds of the ahdo- 

 Ilien. 



