PROTECTIVE COLORATION AND DEFENSIVE STRUCTURES OF LARV.E. 97 



band ; he has, however, not observed any movement in these. He 

 also notices that the larva of Leucoma salicis has, similarly, a pair 

 of small, round, flask-shaped glands, placed close together near the 

 centre of the 1st and 2nd abdominal segments, and which, in later 

 stages, exude a drop of clear, viscous-looking fluid. 



It would appear that these glands are pretty generally distributed 

 among the Liparid moths. Poulton says that in the larva3 of certain 

 Indian Liparids they are usually present. He found two glands on 

 Lymantria concolor, which he considers closely allied to L. (Psilura) 

 monacha. They were also found in ChaerotricJia plana, Charnidas ex- 

 clamationis, Artaxa vitellina, A. scintillans, A. guttata and in Dasychira 

 dalbergiae, although he failed to detect them in a few Indian larvae 

 belonging to this genus. He says that the character is probably almost 

 co-extensive with the family, and that the single gland of our two 

 British species of Dasychira helps to unite these in a single genus. 

 All these eversible glands are " pleurecbolic " and " acrembolic," like the 

 flagella of Centra vinula, and all must possess an axial retractor muscle. 



Patton writes (Can. Entom., xxiii., pp. 42-43) that he found some 

 Limacodid larvaa on liquid-ambar, which, when disturbed, had the 

 power of emitting drops of clear liquid from pores along the edges of 

 the back, the fluid having an odour similar to that of crushed liquid- 

 ambar leaves. The pores from which this fluid is secreted are sixteen 

 in number, situated along the edges of the back, their location being 

 indicated by darker green spots just below the edge. The odour is 

 probably protective. 



In the same way, the remarkable, tubular, fluid-bearing hairs, 

 previously referred to (ante, p. 51), as being common in many larvaa, are 

 supposed by Scudder to have a protective value. He writes : They 

 are usually arranged in longitudinal rows, and their use is wholly un- 

 known. They are a universal characteristic of all butterfly caterpillars 

 in their earliest stage, excepting, probably, the larger part of the highest 

 family, but are common in the later stages of some of the lower families. 

 They are papilla-mounted bristles, each furnished with a trumpet- 

 mouthed tip, and are the ducts leading from glands at their base, secreting 

 a transparent fluid, which, after secretion, is borne in a little globule in 

 the mouth of the trumpet, and sometimes kept in its place by a few 

 microscopic bristles which surround its rim. It probably has a pro- 

 tective function, and is odoriferous, the secretion increasing when the 

 larvae are disturbed. 



Chapman notes that the larva of Jocheaera alni gives off an odour 

 that closely resembles coal-gas. We believe nothing is known as to 

 where the odour is produced, nor of the glands that set it free. 



We have already described certain eversible glands with flagella- 

 like structures on the 8th abdominal segment of certain butterfly larvae. 

 Another gland found on the dorsum of the 7th abdominal segment is im- 

 portant as secreting a sweet fluid, which is much sought after by ants, 

 and in return for which the larvae are protected by the ants from pre- 

 daceous enemies. Scudder says that all Lycamid larvae have the 

 slit on the 7th segment, though all do not possess the gland. 

 In those larvae that do possess it, a vesicular gland of some- 

 what tubular shape is thrust frequently through a transverse slit 

 on the dorsum of this segment. Esper was the first to notice the 

 relation of the larva and the attendant ants. Freyer figures the 



