THE BLOOD AS A REPELLENT FLUID 375 



stance is formed in the blood and also in the genital organs, and is 

 so extremely caustic that scavenger insects which feed upon their 

 dead bodies will leave untouched the parts containing cantharadine, 

 and if May-beetles or mole-crickets are washed with the blood of 

 Meloe or with cantharidate of potassa, it will for several days render 

 them safe from the attacks of the carabids which usually prey upon 

 them. The eggs even after deposition are strongly vesicant, and 

 are thus free from the attacks of egg-eating insects (Cuenot). The 

 Coccinellidse are also protected by a yellow, mucilaginous, disagree- 

 able fluid oozing out of the ends of the femora; in our common, two- 

 spotted lady-bird (C. bipunctatd) the yellow fluid is disagreeable, 

 smelling like opium. Lutz has found that the blood in Coccinellidae 

 passes out through a minute opening situated at the end of each femur 

 (Fig. 362). The blood is very repellent to insectivorous animals. 



The Dyticidse eject from the anus a colorless, disagreeable fluid, 

 while these beetles, and especially the Gyrinidse, when captured 

 send out a milky fluid which appears to issue from the joints of 

 the body. The Silphidse throw out both from the mouth and vent 

 a foetid liquid with an ammoniacal odor. They possess but a single 

 anal gland, the reservoir opening on one side of the rectum (Dufour). 



Other malodorous insects have not yet been investigated; such 

 are the very persistent odors of lace-winged flies (Chrysopa). 



More agreeable secretions, but probably formed by similar glands, 

 is the odor of rose or hyacinth given out by Cicindelse, or the rose 

 fragrance exhaled by the European Aromia moschata. 



Eversible glands of caddis-worms and caterpillars. Gilson, while 

 investigating the segmentally disposed thoracic glands of larval 

 Trichoptera, has found in the larva of LimnopUlus flavicornis that 

 the sternal prothoracic tubercle gives exit to an underlying tubular 

 gland. In Phryganea grandis each thoracic sternum affords an exit 

 to an eversible gland. Many caterpillars, as our subjoined list will 

 show, are very well protected by eversible repugnatorial glands 

 situated either in the under or upper side of the body. Since the 

 time of De Geer (1750) the fork-tailed larva of Cerura has been 

 known to throw out a secretion, which was described by Bonnet in 

 1755 as a true acid, sharp, sour, and biting. This spraying appara- 

 tus in Cerura (Harpy id) vinula has been well described by Klemen- 

 siewicz (Fig. 366, 4), though Kengger in 1817 noticed the general 

 form of the secretory sac, and that it opens out in two muscular 

 eversible tubes, out of which the secretion is ejected. 



The fork-tailed larva of Macrurocampa martliesia, which is much 

 like that of Cerura, when teased sends out a jet of spray to the 



