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WiLDERMUTH (V. L.). The alfalfa caterpillar. — U.S.Dept. Agric, 

 Washington, B.C., Bull. no. 124, 28th August 1914, 40 pp., 20 figs., 

 2 pis. [Received IGth February 1915.] 



It is only since 1910, that Colias (Eurymus) eurytheme, Boisd.^ 

 (the alfalfa butterfly) has been known as a serious pest. It occurs 

 throughout the United States and is now one of the worst enemies 

 of lucerne, causing an annual loss of from £100,000 to £200,000 in 

 Arizona and California alone. The complete life-cycle of C. eurytheme 

 averages about 38 days for all generations, the minimum being about 

 26 days for the third brood and the maximum 64 days for the first. 

 The annual number of generations varies from two in cold districts 

 to six in warm ones. Males usually complete the developmental 

 period several days sooner than the females. Lucerne seems to be 

 the favourite food-plant, but Trifolium reflexum, and T. stoloniferum 

 (buffalo clovers) were probably the original native ones. It also 

 feeds on T. pratense (red clover), T. hybridum (Alsike clover). Glycine 

 hispida (soya bean), Pisum sativum (Canadian field pea), and Vicia 

 saliva (hairy vetch), and other plants. Attempts to rear the larvae 

 from Vigna sinensis (cowpea) failed. In Texas, the larvae aestivate 

 during the dry period in summer when the food supply has become 

 exhausted, but this has never been recorded in the south-west, 

 and the change in habit is probably due to recent irrigation, as the 

 lucerne fields of this once arid country enable it to remain active 

 throughout the summer and to become the pest that it now is. It 

 would be a much more serious one but for its numerous natural enemies. 

 Of 154 pupae collected in Arizona on 26th August 1912, 82 were 

 infested by Chalcid parasites ; 37 destroyed by intestinal disease ; 

 28 partially eaten by Chloridea obsoleta, etc. ; 6 infested by Tachinid 

 parasites ; and only one was alive and healthy. The percentage of 

 para sitism usually reaches its maximum in August, so that much damage 

 is seldom done by the caterpillars after that date. The very common 

 Trichogramma minutum, Riley, seems to be the only egg-parasite. 

 Larval parasites include an Ichneumonid, Limnerium sp. n., Apanteles 

 {Protopanteles) flaviconchae, Riley, and Chalcis ovata, Say, The recently 

 described Pteromalus eurymi, Gahan, is of great assistance in checking 

 this pest and 49 per cent, of the pupae collected by the author in August 

 1912 were parasitised by this species. P. eurymi seems to be distri- 

 buted over a considerable area, being present in Arizona, CaUfornia, 

 Utah, Kansas and Tennessee. It seems almost certain that this 

 parasite winters as a larva within the pupal shell of the host. The 

 combined length of the egg, larval, and pupal stages in the warmer 

 weather of August is from 12 to 15 days, while the pupal stage was 

 found to cover 4 days in the month of August, and 12 to 15 days in 

 February. Phorocera claripennis, Macq., is the most important of 

 three Tachinid parasites, the others being Frontina archippivora, Will., 

 and Masicera sp. A Phorid, Aphiochoeta perdita, has been reared 

 several times from pupae which were alive when collected, and it could 

 not have been acting as a scavenger, but must have been a true parasite. 

 Chloridea {Heliothis) obsoleta (the common boUworm) is often mis- 

 taken for Colias eun/theme by the farmers. It was found to do httle 

 injury to lucerne, but to be a ravenous enemy of the caterpillars of 

 this butterfly, never eating the former so long as it could find the larvae 

 or pupae of the pest. The Melyrid beetle, Collops 

 (CU4) Wt. P12/91. 1,500. 4.15. B.&F.Ltd. Gp. 11/3. 



