PAPER READ. 



Observations on the Life-History of Cha.etoga.edia. monticola. Bigot. 

 BY OTTO H. SWEZEY. 



It is but recently that I discovered the method of egg-laying 

 of this Tachina fly. It is usually stated in entomological litera- 

 ture that Tachina flies lay their eggs on the bodies of their hosts ; 

 in fact with certain species the act has been observed, but for 

 far the greater number of them, the act of egg-laying has not 

 been observed , or at any rate not recorded. That Chaetogaedia 

 had a difl^erent method of laying eggs was surmised, when in 

 June, 1907, this parasite was reared from more than half of a 

 lot of pupae of Agrotis cincUpennis, one of the less common 

 native cutworms. The eggs of this lot of cutworms were 

 hatched in breeding cage and grew to maturity without the 

 possibility of access of a Tachina fly ; hence, considerable of 

 a mystery arose when more Tachinids than moths bred out from 

 the lot. (Proc. Haw. Ent. Soc. I, pp. 163, 164, 1908.) 



This mystery was not cleared up till in February, 1908, when 

 in watching a female Chaetogaedia, as I supposed hunting for 

 caterpillars amongst grass and weeds, I observed that she was 

 laying eggs on the grass leaves. She would quickly crawl around 

 among the leaves, only stopping momentarily to place an egg 

 here and there on the surface of a leaf, never more than one per 

 leaf. They were placed on the leaves of weeds as well as on 

 the grass. After making this observation, it was easy to ex- 

 plain how the caterpillars previously alluded to, become parasi- 

 tized ; for they were daily supplied with food (mostly Sonchus) 

 gathered from outside where Tachinas were common, and had 

 undoubtedly deposited many eggs on the leaves. The cater- 

 pillars ate the leaves v/ith the eggs thereon, which hatched inside 

 and grew to maturity, not however killing the caterpillars till 

 after the latter had transformed to pupae. 



I have since learned that another Tachina fly has similar 

 habits of laying its eggs, the "TJji," which is very destructive 

 to silk worm caterpillars in Japan. This is the only instance 

 I have found in entomological literature of a Tachinid laying 

 its eggs otherwise than directly on the host (caterpillar, grass- 

 hopper, or whatever it is). 



Proc. Haw. Ent. Soc, II, No. 1, Oct., 1908. 



