50 journal op entomology and zoology 



4. The Fourth Generation 

 The first egg-hatching of this generation was observed on Octo- 

 ber 24th. The egg-hatching was continued then to the latter part 

 of November and became suddenly scarce in December. The larval 

 growth was somewhat slow. The young females mostly reached the 

 adult stage in the middle of December, but a few young were still 

 found as late as December 22nd. 



NATURAL ENEMIES 



Like other scale insects, the rose scale has serious natural ene- 

 mies, such as the lady-bird beetles and some parasitic flies. The 

 following enemies were particularly abundant in 1913: 



1. Chilocoriis bivulnerus 

 The well known "twice stabbed" lady-bird beetle preys on the 

 rose scale and maintains a considerable control over the insect. 

 This lady-bird feeds commonly on the rose scale throughout the 

 year In this locality. The female beetle usually lays a single egg 

 under the scale (PI. I, Fig. 23). As the egg of the lady-bird 

 hatches, the larva feeds first on the eggs or young. Both young 

 and adults of Chilocorus bivulnerus feed on this scale insect, attack- 

 ing mostly the young scales. 



2. Scymnus marginicoUis Mann 



This is a tiny, blackish beetle without any spots on the elytra. I 

 found the adult beetles mostly in Spring and Summer times feeding 

 on the rose scale. I have not been able to find the eggs of this 

 beetle. 



3. A hymenopteroiis parasite 



This is a small, black, four-winged parasite not exceeding LI 

 mm. in length (PI. I, Fig. 22). The legs and antennas are pale 

 yellow. A large percentage of young females of the rose scale 

 is destroyed by this parasite (PI. I, Fig. 21). Out of 120 scale 

 insects examined, 48 were killed by these flies. I have not been able 

 to observe the egg-laying habits of this parasite. Its life circle, 

 however, seems to be a short one. This parasite is now in the 

 hands of Dr. L. O. Howard of Bureau of Entomology, U. S. Dept. 

 of Agric, for determination. 



