Eric Mjöberg.
The Mystery of the so-called “Trilobite Larvae” definitely solved.
Psyche 32:119-158, 1925.

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PSYCHE
VOL. XXXII. JUNE 1925 No. 3
THE MYSTERY OF THE SO CALLED "TRILOBITE
LARVAE" OR "PERTY'S LARVAE" DEFINITELY
SOLVED.1
CONTENTS.
I. Introduction ............................................... 119 ................................................ 11. Historical.. 120
........................................ 111. New Investigations. 123
......................................... IV. Neoteinic Females. 128
V. Methods of Securing Males of the "Trilobite-larvae". .......... 131 ................
VI, Supposed Luminosity of the "Trilobite-larvae". 132 ... VII.
The First Known Male and Female of the "~rilobite-larvae". 133
...............
VIII. The Systematic Position of the Genus Duliticola. 137
IX. Food Habits of the i'Trilobite-larvae". ........................ 140 ............ X. Different Species of "Trilobite-larvae" from Borneo. 142 .....
XI. "Trilobite-larvae" from other Parts of the Oriental Region.. 144 XII. General Discussion of the Development of Lampyridae, Drilidae, .............................. Telephoridae and Lycidac. 145 .............................................. XIII, Bibliography.. 151
Among the many remarkable forms of insect life to be met with in the Oriental region none have aroused the interest of entomologists more than certain strange looking uncouth creatures, showing a great resemblance to the extinct trilobites in possessing protruding lateral processes on the abdominal seg- ments. From time to time various "trilobite-larvas" as they have been termed by English entomologists, have been figured and more or less superficially described. Although the first one was made known in 1831 by Perty no one has been able to breed them and state what they really are. They have been a standing 'Contributions from the Enton~ological Laboratory, of the Bussey Insti- tution, Harvard University, No. 249.




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120 Psyche [June
puzzle to entomologists and for nearly a hundred years their systematic position, method of propagation, food, etc., have re- mained a mystery.
In the year 1831 Perty described a peculiar beetle-larva which he called "Larva singularis" or "Larva qucedam et Java." He seemed to be inclined to regard it as the larva of a necroph- agous rather than of a malacoderm insect and adds: 'Ti deter- minandum est cujus imaqinis haec larva sit." In his "Introduction to the classification of Insects') (1839) Westwood mentions the same larva and refers it preliminarily to the Lycids.
Furthermore he describes and figures a smaller larva with more nearly parallel-sided body, which he also con- siders to be a Lycid larva.
Some years later (1841) Erichson refers to a similar larva and believes it to be a Lampyrid. This opinion was shared 20 years later on (1861) by Candkze.
In 1887 or some 26 years later Kolbe discusses the "trilobite- larvae "and inclines to Westwood's opinion that they are Lycids. A larva referred to in 1887 by Lucas with "mandibules grands, arquee robustes" and with "plaques lumineuses" from Siam is apparently a Lampyrid-larva of some kind. In 1899 Bolivar describes and figures two "trilobite-larvae" of the broader type, one from Borneo and another one from the Philippines under the title "DOS formas larvarias de lampirides." Concerning their systematic position he seems to be in doubt. A figure of one was sent by Bolivar to Bourgeois, who in reply makes the following statements: "Quant ii cette de Philippines elle est tout autre et je ne serais pas 6tonn6 qu'elle n'appartient pas au genre Lycus. Quoi qu'il en soit, cette larve de Philippines est de plus interessante et il serait fort a souhaiter que nous puissions &re edifies bient6t sur les m6tamorphoses ii quelle espece nous devons la rapporter."
An examination of Bolivar's figures makes it clear that both larvae are of the "trilobite" type. The one from Borneo is obviously the most common lowland form, which has repeatedly been figured or described by various authors.



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1.9251 Mystery of ~rilobite Larvce" Definitely Solved 121 The same year (1899) Dr. Sharp describes and figures a peculiar larva from New Britain in the following words: "There have long been known to entomologists some extremely re- markable larvae, that probably are Lampyrides or Lycides, though none of them have been satisfactorily identified. Dr. Willey procured a most remarkable form of this kind, bearing longabdominal processes that are segmented or articulated at the base (PI. XXXV, Fig. 7). ('1 take the opportunity", he adds, "of drawing attention to these forms with the hope that someone may soon be able to give us 'further information about them." There can be hardly any doubt that the larva referred to is a Lampyrid larva, though of a very aberrant and ext,raordinary type.
In an article in the SarawakMuseum Journal (No. 3, 1913, pp. 61-65) Mr. Gahan deals in detail with the mysterious "trilobite-larvae" and discusses the future possibilities of solving the problem which they present. He recommends strongly that tropical entomologists attack the problem in the field and make renewed attempts to rear them, pointing out, however, that larvae have been kept alive a long time, extending up to two years, but so far without success.
The late Curator of the Sarawak Museum, Dr. R. Shelford, in his posthumous work "A Naturalist in Borneo'' edited by Prof. Poulton, has dealt at length with the "trilobite-larvse." He devotes several pages to these myst,erious creatures, from which I extract the following:
Page 172: "If, then the adult male of the 'trilobite-larvse' is provided with wings and wing cases, then the larva should possess imaginal rudiments, but a careful microscopical exam- ination of male larvae ranging from a comparatively small size to nearly the largest has failed to reveal the slightest trace of these organs. I can therefore declare with some degree of con- fidence that if an adult male of this larva be eventually found differing in its external anatomy from the larva, then it must be apterous. In spite of the abundance of these larvse, in spite of the fact that they have been known to collectors for many years, a male of this description has never been found. I will venture to prophesy, moreover, that it never will be found, but



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122 Psyche [June
that some day a larva with completely developed internal gene- rative organs communicating with the exterior by ducts will be found and such a "larva" will be to all intents and purposes an adult. If this is ever established, we shall have a gradual tran- sition from species exhibiting complete metamorphoses to species without any metamorphoses at all as thus: Males and females undergoing complete metamorphoses. ........ Lycidce etc.
Males and females undergoing 'complete metamorphoses but female larviform. ....................... Lampyris noctiluca. Males undergoing complete metamorphoses; females not meta- morphosing. .................................... Phengodes Males and females undergoing no metamorphoses, both indis- ................. tinguishable from larvae. " Trilobite-larvse". What Shelford means by "having examined male-larvae ranging from comparatively small size to nearly the largest is certainly very difficult to explain. Obviously he presumes that some of the "trilobite-larvse7' commonly met with in the nature must be male-larvse and therefore all his conclusions based upon this wrong supposition are wrong. For all "trilobite-larvae" reared by me-and they number more than 50 and belong to three different species-have turned into females and we can therefore safely conclude that all the common "trilobite-larvae" we find crawling about in the jungle are female-larvae. What furthermore seems to have puzzled Shelford is the extraordinary size of the larvae. He states that "neither in Kina Balu nor in the neighborhood of Kuching, where 'trilobite- larvae' also occur does there exist, so far as known a Malacoderm beetle that could possibly be regarded as the adult in either of these families and this in spite of the fact that in the one place the larvae are extraordinarily abundant and in the other common enough."
/
It deserves furthermore to be pointed out that Shelford's above quoted statement about Phengodes is misleading. As we shall see later on, the members of the peculiar American group Phengodini pass through a long pupal stage and the larviform



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19251 Mystery of "Trilobite Larva" Definitely Solved 123 female shows certain distinctive features in comparison with the larva.
The latest author to deal with the "trilobite-larvse" is Gravely in his paper "The Larvse and Pupse of some Beetles from Cochin" (Records of the Indian Museum, Vol. XI, part V, No. 20, 1925). He describes and figures the larva of Lyro- pceus biguttatus, which in general type resembles the "trilobite- larvse" although it is considerably smaller in size. The larva developed normally into a pupa and imago. Gravely states that "the larvas which give rise to these winged insects are, however, not particularly large and throw no certain light on the status of the much larger insects with which the name "trilobite- larvse is more particularily associated." Gravely also refers to two large insects of the "trilobite-type" which were found in the Cochin forests.
They are figured on
plate XX and measure about 28 mim. He also mentions another larva of much smaller size also from Cochin, which has more elaborate tubercles and papillae and differently constructed mouthparts, He suggests that these former larvse may prove to be immature females of the Lycid genus Lyropm, but leaves the question open as nobody has been able to trace their life- history.
On arriving in Borneo in May 1922 I made up my mind to have the problem of the "trilobite-larvse" of Borneo definitely solved more especially as my interest for these peculiar forms of life had been already aroused during my sojourn in Sumatra in 1919-21, when I came across a single representative of "Perty's larva" in the jungles of Siantar.
It has long been known that these peculiar larvae reach their maximum of size in Borneo. So far as I have been able to ascertain at present two distinct types have been recorded from there and superficially described. To this I am glad to add four more, making a total of six species. One of them is a very striking form, measuring nearly 70 cm., quite black with a serie of sealing-wax red tubercules on the dorsal side. It is figure



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124 Psyche [~une
on Plate I11 fig. 1 and is the largest and most conspicuous form known so far.
Since 1922 I had a large number of the larvae under close observation and have made every effort to rear them. The first species that came in my way was the large attractive larva just referred to above. It was found quite commonly on the higher slopes of the unknown Mt. Murad, a high mountain situated in the North of Sarawak not very far from t,he Dutch boundary. Over 200 specimens in different stages were secured and kept alive in suitable cages, but none of them underwent any meta- morphoses. Most of them were brought along six weeks later on when I returned from Mt. Murad on my way back to the Baram Station on the lower Baram River. Owing to the awkward conditions of transportation where everything had to be carried on the natives7 backs, many of the larv* died. The sudden change in temperat,ure from the cold mountain regions down to the steaming hot lowland naturally aided in reducing the number.
In January 1923 I undertook an expedition to Mt. Dulit (4000-5000 ft.). The number of surviving larvae, about 30, were taken along, but soon died.
Out of more than 200 larvae
only a single one developed into an adult female, distinguished from the full-grown larva only by possessing a sexual opening in front of the anal disc, surrounded by two simple genital valves. It lived for some days but owing to some difficulties in casting the skin on the apical segments it soon shriveled, became dis- colored from a black secretion and died. A dissection showed t'he ovaries full of small whitish eggs, convincing me that I had to do with a sexually mature, fully developed female for t'he first time.
When arriving at Mt. Dulit on the Tinjar River, a large tributary to the Baram River, I found to my great surprise that another "trilobite-larva" of large size and of apparently unknown type was fairly common on the higher slopes from 3500-4500 feet. It is the big black larva of the type shown in Plate I11 fig. 2. On returning to my headquarters in Kuching in March I brought more than a dozen very large larvae with me. These were fed on decaying jungle wood, which was changed daily.



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1925 Mystery of "Trilobite Larvae" Definitely Solved 125 After some weeks of captivity one of the larva rolled itself up and was lying on the surface as though dead for several days. One morning I found that it had cast the larval skin and ap- peared quite whitish. It remained in that position for another five days whereupon the color changed into a dull ycllowish- white.
It soon started to crawl slowly about.
A close exam-
ination revealed the interesting fact that it had developed a sexual opening on the eighth sternite surrounded by two small valves immediately in front of the anal suction disc. Some days later on it started to lay eggs. These were small, whitish, perfectly round, measuring about one millimeter in diameter. They were deposited in small groups here and there or simply dropped wherever the female was crawling, sometimes as many as 15-20 at the same place. Egg-laying went on for about two weeks until over 300 eggs had been deposited. Every morning, when opening the door to the cage I found the female turning the top of the abdomen upwards in order to expose the sexual opening from which a clear drop of liquid was secreted. Three more larva cast skins after a similar period of rest and turned into sexually mature females behaving in exactly the same way as the first one described above. They all died after having deposited from 300-400 eggs. Some months later more females developed, but no signs of any males could be seen. In October I undertook a new expedition to Mt. Poi in Southern Sarawak. There I came across the very same big black larva just referred to.
They were found at an altitude
ranging from 3000-5000 feet and were quite numerous. Several developed into females and were exposed at suitable places in the jungle in hopes of attracting the males, but without success. The females were tied up with a string long enough to allow them to move about in a circle and were protected by a cage of wire netting with meshes more than an inch wide. Thus the males could easily gain access to the cages and the females were comparatively free but at the same time well protected. All efforts were, however, in vain.
I had to return again to
my headquarters. During the following month (December) my native collectors brought me more than 200 big larva of the same type from another mountain, Batu Gadin, in the Lundu district,



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126 Psyche [June
where they had been despatched exclusively for the purpose of collecting "trilobite-larvae." Of these more than 20 developed into adult females in quite the same way as the ones previously referred to. As no signs of males could be detected it became now more clear to me that the "trilobite-larvae" commonly met with in the various localities must all be female larvae. In January 1924 I set out for a third expedition, this time to the second highest mountain in South Sarawak, Mt. Pen- rissen (4000 feet). The main object was to follow up the search for the males of the mysterious larvae, all the available female material was brought along in two big cages. My sup-
position that the same type of larvae probably would be found also on Penrissen turned out to be quite correct, for several larvae of the same or at least very similar kind though not quite so big were found in close vicinity of my camp. A number of newly developed females were immediately exposed in the same way as described before. As many as 18 cages were kept going. They were carefully examined three times a day, the first time always at sunrise. But although over a month was spent on the big mountain, covered with a luxuriant jungle, no traces of any males could be found. It deserves to be mentioned that all "trilobite-larvse" found on Mt. Penrissen were only half grown and showed more pronounced light markings between the dorsal rows of tuber- cules than the form from Mt. Dulit, Mt. Poi and Mt. Batu Gadin. It is therefore possible that it might have represented another species or sub-species and that both these facts may have been reasons why I did not meet with any success in capturing the males.
I returned to Kuching, determined not to give up my efforts to secure the males. As all the larvae of the developed females had been collected on Batu Gadin, this place could be regarded as their true home and I therefore decided to move my base of operations there. In April 1924 I proceeded to Lundu and from there directly to Batu Gadin where my headquarters were erected at an altitude of 2500 feet.
During two weeks I supervised the experiments myself. Females of the ordinary types as well as of the smaller more



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19261 Mystery of "TriIobite Larva;" Definitely Sobed 127 parallel-bodied kind which I had also been successful in breeding, were exposed at selected places but all in vain. As other duties called me to Kuching I had to return leaving, my collectors .
behind with inatructions to report immediately if any males should appear in the cages.
During more than two months this tedious work was kept going without the slightest results. In the meantime I visited the place twice making some slight alterations. The native collectors lost all hope, complained about the cold weather and wanted a change.
I gave, however, orders to move the experimental base 1000 feet higher up, where big larvae seemed to be more plentiful, as the attempt to get the males had to be continued. A reward of $10.00 for the first male stimulated the collectors very much in their efforts.
I returned again to Kuching but heard nothing from my collectors during the following weeks. I visited the place again and made several alterations placing the cages in more open places, exposed to the weather and wind, here and there clearing patches of the dense jungle vegetation.
This proved ultimately to be successful for one morning a male was caught in copula with a female. (Plate IV fig. 1). I was just on my way back, when one of my collectors came running after me with the copulating pair wrapped up in a banana leaf. At the ventral side of the big female a small black beetle was seen firmly attached and with his tip of the abdomen deeply inserted in the female's sexual opening. It soon detached itself from the female and waa preserved in alcohol. The female was brought back to Kuchiag where it soon started to deposit a large number of eggs, but unfortunately they never hatched out. Probably the male had been too much disturbed and the eggs had not been properly fertilized. My collectors received strict orders to carry on the ex- periments in order to secure as many males as possible and to watch carefully the eggs deposited by the females. Four mom weeks' work yielded a dozen more males of exactly the same type as the first one. It was therefore evident that I had, after all my trouble and effort, secured the proper male



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128 Psyche [June
All deposited eggs were brought down to Kuching by the returning collectors, but for some unaccountable reason, not a single one hatched. Evidently the sudden change in altitude and temperature between the cold mountains and the hot low- land must be responsible for their failure to hatch. As already stated females of the smaller and more narrow type of "trilobite-larva" had also been exposed, but no males were ever found. The females deposited about 100 eggs each. In spite of the female of this type being much smaller than the first one its eggs, as seen on Plate IV fig 2, are curiously enough twice as large.
Thus nearly two years of more or less continuous field work had resulted in rearing three species of "trilobite-larvae" to egg- producing adult females and in the capturing of several males of the second largest species.
All my attempts to rear the very common, flat, leaf-like lowland species figured in Plate I11 Fig. 5, had been a failure. Although the larvae were kept by me in hundreds in cages not a single one turned into a female. When attaining their maximum of size they were all attacked by a whitish mould which killed them in great numbers.
The only way to rear this species seems to be to build big cages in the forest and to keep some hundred of the largest ones in captivity under conditions as natural as possible until the females develop like the other species. The larvae feed on decaying old wood. This type of larva is extremely abundant and it would be more interesting to get its male which, for reasons given below, probably represents a new genus. IV. NEOTEINIC FEMALES.
A closer examination of the "trilobite-larvae" from Borneo thus reveals the interesting fact, that the "trilobite-larvae" so commonly met with are the female-larvee of Lycid beetles of various genera and that the females undergo, practically speak- ing, no metamorphoses at all. They attain sexual maturity as complete larvae and differ in their organization only by possessing developed ovaries and a sexual duct and opening. They are



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19251 Mystery of "Trilobite Larva'' Definitely Solved 129 adults retaining infantile characters and can therefore be termed neoteinic in the definition of GIARD (1905). The males on the other hand are well developed beetles probably hitherto un- - described but in all essential characters normally developed Lycids.
The female has so completely reduced her metamorphoses that in her external features, she is perfectly larviform. No marked pupa or imago-stage exists. As a worm-like creature she crawls sluggishly about on the ground and dies after having deposited her numerous eggs. Copulation and oviposition take place in a quite normal way. The female has specialized in the direction of larger size, premature development of the sexual organs and in reducing the normal metamorphoses to an ab- solute minimum.
It seems certainly strange that the female after the last ecdysis remains whitish and unpigmented. A close examination, however, shows that a diffuse casting of skin takes place after the development of the sexual organs, or in most cases after oviposition, when the body shrinks together and therefore the thin transparent skin becomes more conspicuous. (Plate I11 Fig. 2a).
This partial casting of the skin seems to be more or less confined to the dorsal side and is probably the last reminiscence of a former regular pupal stage, which we must suppose the female to have possessed during earlier geological periods when it was more similar to the male and not yet so highly differentiated in the way of retrograde development.
It deserves in this connection to be mentioned that many, if not all of the normally developed Lycids show a distinct ten- dency to retain the last larval skin when pupating. When in Borneo I bred hundreds of the gregarious larvae of Lycostomus gestroi Bourg. They all kept their skin when pupating. The advantages of this are apparent. The larvae are black with bright yellow markings, which serve as warning colors. Their principal enemies, birds, reptiles and carnivorous insects know by experience their nauseous properties and a Lycostomus larva is therefore never attacked. The insect makes use of the '