320 NATURAL HISTORY OF ARTHROPODS. 



Among the many insecticides wliicli arc used to reduce tlie numbers of Doryphora, 

 Paris green and London purple are generally considered best. Paris green, or as it is 

 sometimes called Scheele's green, is an arseniate of copper often used as a pigment. 

 It is extremely poisonous, and is diluted with twenty times its weight of flour and 

 sprinkled with a sieve upon the potato-plants. London purjile, which is a waste 

 product of anilin manuf;icturc, contains al)Out forty per cent of arsenic, and although 

 very much cheajier than Paris green it is still more poisonous, and is used in the same 

 way, diluted with about thirty-six jiarts of flour. In all cases where these jioisons are 

 used cattle should be carefully excluded from the fields. 



Severe cases of poisoning from handling the beetles themselves, in quantity, have 

 been reported: likewise the vapor arising when they are killed by scalding is said to 

 be jwisonous. While such cases of poisoning are apparently authentic and are not 

 improbable, yet the question of the poisonous nature of Dorijphora is one that requu'cs 

 much furtlier careful investigation than it has received. 



Very closely related structurally to Doryphoru., which is itself sometimes retained 

 in the genus Chnjsomela, is C. divicollls and C. scalans. C. cUoicoUis, which is 

 often called ('. tn'macuhita, is about 0.4 inch long, with deep blue head, 

 l^l^X^ thorax_, antennre, legs, and under-side, while the elytra are reddish orange 

 y^gll with a few blotches of black ujion them. Its reddish larva, which re- 

 "O'^^T^ sembles in form that of JJoi-i/phora, feeds, like the imago, ujion species 

 ,, ^... ,y< of milk-weed (Asckpias). C. scahifis is one of a o-rouii of chrvsomelids 

 snmeja ciiid- -\\lii(.]i bave the elytra covered with curious hieroglyphic stripes and mark- 

 ings, whence they have been given T)y some authors the generic name of 

 CalUijriipha. The greenish-black and white imago, which is about 0.3 inch long, after 

 jjassing the winter imder leaves and in rubbish, appears early in the sjiring upon elm 

 and linden trees and on the alder. Its eggs are deposited in May and June, and the 

 larvpe of the first brood reach full growth by the end of the latter month. The larvre 

 have similar form to those of Don/phora, but ai'e whitish, somewhat sjiotted with black. 

 Similar species of CalUyraplia are found on the hazel ( Cori/his), on Viburnum, and 

 on willow (Sali.v). 



In southern Europe the larva of Chrysomcla (liluta is luicturnal, as is the case with 

 some lepidopterous larva?, and comes out of its hiding places where it spends the day 

 to feed upon a species of plantain {Flantayo coronopus) at night. The larvre of a few 

 chrysomelids have a habit, when disturbed, of forcing out upon the tips of s]iines which 

 are arranged in rows alonsj their bodies, little drops of a disagreeably odorous milky 

 fluid. These drops of a secretion, which is, of course, defensive in function, can be 

 again witli<lrawn into the spines when danger is past. Professor C. Claus found 

 salicylic acid in the larva of C. ^lopuli, the Euro]iean s])eeies in which this peculiar 

 secretion has been most studied. In America larva^ of Plac/iodera scripta, P. lap- 

 ponica, and P. trcimda have similar secretions. 



Gasfrophysa 2}oIi/f/o?ii is an oblong beetle, about 0.1.5 inch long, of which the 

 prothorax, legs, and basal joints of the antennse are reddish Ijrown, the rest of the 

 insect shining blue, except in the case of females when they are much distended with 

 eggs; then the jiortions of the distended abdomen which the elytra cannot cover are 

 yellow or yellowish lirown. This beetle is very aljundant from April to September 

 upon common knotgrass {Polygonum ((vicidare) both in Europe and in America. 

 The groups of yellow eggs on the leaves of the knotgrass hatch in from eight to eleven 

 days. The yellow laiTse resort to the ground for ]iupation. There are two or three 



