567 



capable of reproduction. Several generations can occur in a year, 

 and at high temperatures a new one can appear in seven days. 

 H. hrevicornis has a more rapid sequence of generations than 

 E. kuhniella ; at a constant temperature of 25° C. [77° F.] it is 7-8 

 times as rapid. 



The economic value of this parasite is therefore considerable, though 

 a relatively high degree of warmth is required, development being 

 slow under 64° F., and oviposition ceasing in cool weather. H. hrevi- 

 cornis cannot be employed as the sole means for controlling 

 E. kuhniella, but, provided that the Braconid is properly bred and 

 liberated, it can prove a useful auxiliary in retarding the increase of 

 the meal moth, so that long intervals may elapse between the dates 

 when fumigation is required. 



ScHULZE (H.). Beitrage zur Biologie von Tyroglyphiis mycophagiis 

 (Megnin). (Zerstorung einer Mehlwurmzucht durch diese Milbe.) 



[Contributions to the Biology of T. mycophagiis. The Destruction 

 of a Brood of Tenehrio molitor by this Mite.] — Arh. Biol. 

 Reichsanst. Forst- ii. Landw., Berlin, xi, no. 2, 1922, pp. 169-177, 

 6 figs. 



In the hypopial stage Tyroglyphiis mycophagiis, Megn., uses insects, 

 in this case Tenehrio molitor, as a means of transport for the purpose of 

 reaching new feeding-places. As many as 700 mites may occur on one 

 beetle. 



The adults and eight-legged nymphs of T. mycophagiis parasitise the 

 larvae, pupae and adults of T. molitor, first attaching themselves at 

 points where they cannot be brushed off and then penetrating into 

 the host. The eggs of T. molitor are laid in positions so dry that they 

 are not subject to attack. 



Another mite, T. longior, Gerv., was also found in the bran used in 

 breeding Tenehrio, but appeared to limit its attack to dead adults 

 and pupae. T. longior does not possess the caustic secretion that 

 enables T. mycophagiis to attack successfully the pupae and larvae 

 of the beetle. 



ScHULZE (H.). Die Bekampfung von Tyroglyphiis mycophagus 

 (M6gnin). [The Control of T. mycophagus.] — Arh. Biol. Reichsanst. 

 Forst- n. Landw., Berlin, xi, no. 2, 1922, pp. 179-184. 



In testing methods against Tyroglyphus mycophagus, Megn., infesting 

 an experimental brood of Tenehrio molitor [see preceding paper], 

 all stages of the mite were destroyed by exposure for three hours to 

 Zyklon (a derivative of hydrocyanic acid), 15 cc. per cu. m., or for two 

 hours to chloropicrin, 10 cc. per cu. m. Both strengths were, however, 

 fatal to T. molitor, so that fumigation proved unsuitable. Desiccation 

 was more successful, the damp bran containing T. molitor and the mites 

 being dried by simple exposure in a warm room at 23°-25° C. 

 [73-4°-77°F.] for 5-6 days. 



Points to be noted are that a brood of T. molitor may become 

 infested with mites if even a single beetle carrying the hypopial stage 

 of the mite is introduced, and that if damp bran is placed with dry bran 

 any mites present in the latter will be attracted. This indicates a 

 means for detecting mite-infestation in flour and bran in which no 

 larvae, nymphs or adults can be seen. 



