46 BULLETIN 416, U. S. DEPARTMENT OF AGRICULTURE. 
TABLE X V1.—Rate of destruction of red spiders by the larva of Chrysopa rufilabris—Con. 
| Red spiders consumed. 
Length 
Feed- | Total 
nee 4) Hatched. | | Total | Pupated. eee ing |feeding 
ee 13th | 14th | 15th | 16th | 17th | 18th for al ays. | days. 
day.| day.| day.; day.| day. | day. |} larval eee 
| period. 
1914. | | 
Pee ou Snlylg- 2s Opes eee Weer pete Oe hee ea ees Put owe 1| 
Bis: Tiily 1S. sean Ie een eee ear fore CER TEP Oia Oo ee eR ees 5 
Soe ae Wes Gos Fs. Ne snsce [ose eh alte ac Sls ee ee a ee a ee ee ce eee 7 
ee is | Aug.3 77| 99| 110] 224] 119] 198] 1,250] Aug. 22 18 18 
eee as | SSB eee |e ee sBeialettyaseled cea. SS ek eee ee ei cee | eee ree ee one oe 3 
Boost ae Sul yaAStes ele era ee ey eee eee se eal eee A EE tee, eet a eS a! [ee 7 | 
ieee July (6.0 hat. Eee ell ane [te pe ae lS ere er ee) Sees Oe 8 | 86 
islets July 191 (| TON 440) 1995 1 oe ee silty 50 ee 10 
Sees | ae ae One 58 117 VAT 5220-4 DG 3] S20 ial een es SN AGT OO, Celie 2 ae 9 
10525 Aug. 222. 80 | 106 BT Dey Resale! 1) L7G (aa UT hs | pes dO les Sas Ok seme 6 
ito Uriah Por conve pag ©) (eben a oie: {27g ASB, beans IAD, Gas en 2 
1 Ae Aug ls sees ee 145 189 129 | 193 |- ECE api le 4 |) 
Beemer Aue S202 See 98 129} 219 130 | 208 | mic ac beni Ang. 262 » aie 5 |) 
1Collected as half-grown larva. 3 Collected as mature larva. 
2 Collected as two-thirds grown larva. 4 Collected as large larva. 
In summarizing Table XVI it is found that 6,956 adult red 
spiders were consumed by 13 Chrysopa larve in 86 feeding days, or 
an average daily consumption of about 81. The one larva for which 
complete data are recorded consumed altogether 1,250 mites. The 
largest daily feeding was 224 mites. As the larva grows the appetite 
increases remarkably so that an individual which ate only 20 mites 
per day following hatching will consume ten times that number just 
prior to pupation. Larve numbers 8, 9, 10, 11, 12, and 13 were 
collected in the field in various stages of maturity, so that only the 
feeding of the finai days can be shown. It is probable that the 
figures consistently represent the normal activity of this species 
as a red-spider eradicator. The appetite for mite eggs was not 
determined, but we have often seen larve in the act of devouring 
them. Probably numerous eggs were eaten along with the mites in 
all the foregoing records. Three minutes appears to be the average 
time required by iarve in devourmg a mite. 
We have foliowed the process of the fabrication of the cocoon of 
Chrysopa rufilabris from beginning to end. Working in a looped 
attitude, the successive layers of silk are secreted from the tip of the 
abdomen, which is moved shuttle-like from side to side. Contrary 
to long-accepted belief, it has been established that the circular lid, 
which permits the exit of the adult fly, is prepared by the larva as 
the last act before entering the resting stage. 
During the four seasons of our investigations at Batesburg it has 
been determined. that a considerable percentage of mortality to 
chrysopids arises through parasitism. The results of a series of 
studies on lacewing-fly parasites has been published. (McGregor, 
1914.) In a series of 99 cocoons collected in the field, 48 yielded 
