()8 POOD UABITK OF TUV, rffiOSBBAKS, 



AMMAL I<'I)0I). 



Insects and other animal iiiatlci' <'iitc'ii by the black-headcxl gros- 

 beak amount lo ahnost twice the bulk of the vegetable food, or (15.85 

 percent of the total HubHisLencis. These, then, Khould l)e regarded as 

 the really staple foods of (lie si)eeieH. While no Hinfi;le vefjjetablc, ehs- 

 ment was fed ujjon by more than 41 jL^roslxiaks, certain itorriH of the 

 insect diet were chosen Ity more; than a humJred, or over iialf of the- 

 birds examined. This fiiet sn^f^ests that if the majority of llie inseiits 

 preyed ujjon are noxious, the be.nefils conferred by the bird j^'rcatly 

 outweif^hs the injury inflicted. 



Corning, then, lo Uw, e(!onomic status of the insects devoured, it 

 appears from the results of the (examination of ii2(') Htoniachs that 8.;i7 

 percent of the l)ird'H /food consists of f^round beelles, Hreflies, and 

 ladybirds, which usually are considcired beneficial; '2.50 jxtrauit is 

 composed of wasps, ants, bees, c^tc, some of which are very useful, 

 some iiino(^uoiis <>v harmful; and. 1.17 fjercent is miide- np of a f^n^at 

 number of unrelated items, lai'gely of neutral import, which, owing 

 to the faci that they -An: rarely eaten, liave little sijuiiilicatK^e. Thus 

 58.75 percent, or nearly Ihree-fifths of the entire food, is composed al- 

 most wholly of insects which are a constant mcinace, (o agriculture. 



Of the above classes the beneficial kinds deserve first consideration. 

 The most important among them numerically an; fin^flies (Lam- 

 pyrida;), which are almost finiforrrdy carnivorous, both lis larva- and 

 as adults. Hince (h(!y do much to chexdc the iruirease oii many other 

 insects, the destruction of large numbcers would be injurious. I''ifty- 

 two of the grosbeaks examined had fed ufjon fireflies to the extent of 

 2.38 percent of the whole food. Both ndults and larva- w(!re capt iintd, 

 from 5 to 1!) of the former and from 12 to 30 of th<! lattia- being found 

 in some stomachs. 



Among other useful insects which are attacked by (he blackhead 

 are the ground beetles (Carabida-). Xinetwn grosbeaks ate them, 

 and they amount to O.'M percent of the food. Since so few <i( these- 

 beetles are captured and as certain of them at times f(!ed upon f)lantH, 

 the injury is too slight to be noticed. 



Thre(! black-headed grosbeaks ate small ladybird beeth-H which [jrc-y 

 upon scal(- insects and plant lic(!, two of them securing spc-cimens of 

 an Australian coccinellid {lihizoiivs ventraUs, fig. 88), which was 

 introduced into California for (In- exfinws purpose of destroying scale 

 insects. If tlu; grosbeak destroyed many of these becithw, the Itird 

 would have to be givftn a black mark, but when it is considfTcd that 

 the blackhead feeds ufjon scale ins(!cts a large part of the timi- (more 

 than a fifth of its food consisting of scales), it is surfn-ising that so 

 few of the ladybirds an; devoured, 



(Jonsid(!rafjl(! liking, however, was shfiwn for another group, the 

 Hymenoj)tera, part of which at least are ben<-ficial. The rriost usr-ful 



