INTBODUCTION. 7 



by two adult beetles, occupying the end of the gallery, which 

 was largely Hljcd with |)ulveriz('(l wood, often boring further 

 into the wood, while closu behind them were the larvae, varying 

 in number from 2 to 7, sometimes in pairs and sometimes 

 scattered. 1 now put the larvai foinid in a single trunk into 

 a breeding-cage together with the two beetles and found that 

 they i)rospered quite well. If 1 removed the two beetles 

 the larvae died, even if I gave them the food-material chewed 

 by the beetles confined separately. As I frequently observed 

 both in the Held and at liome, the larvae ate only the wood 

 chewed by the beetles. If I took a larva from its burrow 

 and examined its mouth-parts I always found between them 

 only spongy chewed woody material and never separate 

 pieces such as one always finds between the jaws of larvae of 

 Lucanidae, Rutelidae, Dynastidae and Cetoniidae. If one 

 carefully examines the mouth-organs of a Passalid larva, one 

 finds that they are not of a kind to masticate the wood in 

 which one finds them. The mandibular teeth are compara- 

 tively feeble and the grinding surfaces at the base are both 

 concave, without ridges for mastication, and lie so far apart 

 that their edges are not in contact ; moreover, the lower lip 

 is without the chitinous piece on the inside, the hypophar^Tix, 

 which is found in all wood-eating Lamellicorn larvae and which 

 serves to grind still smaller the wood wliich has been partly 

 divided between the molar surfaces. The maxillary teeth 

 can only grip and not masticate the food. 



The operations of the pair of beetles found together with 

 the larva? are, however, not confined to masticating their 

 food, for if one gives the larvae the pulverized wood gnawed 

 by the beetles removed from them, or that taken from the 

 burrows of other LameUicorn larvje found in the same stump 

 (e. g. Rutelid or Cetoniid larvae) the larvae die nevertheless. 

 Although I could not investigate the chemical constitution of 

 the digestive secretion in the moist woody substance eaten 

 by them, I consider it certam that the food of the larvae 

 is predigested by the beetles. The brevity of the digestive 

 tract in Passalid larvae is confirmation of this. In them the 

 enlargement of the last abdominal segment characteristic of 

 all other Lamellicorn larva?, including those of Lucanidae, is 

 entirely wanting. 



Examination of the internal organs of the two beetles 

 found with the larvae always proved them to be a pair, the 

 parents of tlie larvae, as further observation soon showed. 

 A pair gnaw their way into a suitable stump. They are not 

 particular in their choice, one finds few old stumps near 

 Petropolis witliout P«.s%s'fli».s ; they attack any kind of wood, 

 provided it is sufficiently decayed and quite moist. The 

 burrow^s, which are so wide that botli beetles can work in 



