S. Madwar.
The Biology and Morphology of the Immature Stages of Macrocera anglica Edwards.
Psyche 42(1):25-34, 1935.

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I 93 5 I Zmmture Stages of Mawoeera anglica 25 THE BIOLOGY AND MORPHOLOGY OF' THE
IMMA-
TURE STAGES OF MACROCERA ANGLZCA
EDWARDS.
BY s. MADWAR, PH.D. (CANTAB.) M.B., CH.B. (EDINB.) Research Institute and Endemic Diseases Hospital? Public Health Department, Cairo, Egypt
The early stages of this fly are unknown and they are here described for the first time. The remarkable shape of the larva, resembling more a small earth-worm than the larva of a fly, makes it an interesting object of study. The records of the British Museum show that the fly was found in the New Forest, Stocken Church, Crowborough and Welwyn.
Moreover, I have seen specimens. of this fly from Egypt in the British Museum.
They were darker than
the English type.
I found the larv~ of Macrocera under the loose bark of damp moist logs of oak, ash and elm in Richmond park and Epping forest near London. The bark was stripped gently? and the larvze were found living separately each under its own web of saliva. The web is hygroscopic and on it are suspended droplets of clear fluid. The web consists of fine threads about three to four inches long. In constructing this
web, the larva anchors one end of its slimy salivary thread to the bark ; the head is then raised, and the thread is worked forwards and backwards. Inside the web, a stouter thread runs from one end to the other.
The movements of the larva are very characteristic. It glides with greatest ease and even with rapidity over the even surface of fungoid growth covering the bark. In do-
ing so, it is\ assisted by the fine threads which it emits so as to bridge over these inequalities. It moves forwards and



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26 Psyche [March
backwards with equal facility. Sometimes it turns by re- versing its head and gliding along its side. When the larva is full-grown? it advances to one extremity of the web a,nd forms outside it a curious little mass of silken matter? so irregularly formed that it is scarcely entitled to be called a cocoon.
The body is then shortened and the
thoracic region is markedly thickened. The skin of the larva splits along the mid-dorsal line and the pupa draws itself forward leaving the old larval skin behind. If undis- turbed, the imago often remains quiescent for 3 to 4 days, but will rush out with amazing celerity at the slightest dis- turbance.
Luminosity
In a closely related species? CeropZatus sesioides, Whal- berg (1848) was the first to state that the larva and pupa of Ceroplatus were luminous. Norris (1894) gave an ac- count of the luminosity of the New Zealand "glow worm." He further suggested that the light emitted from the larva helped to attract small insects which the larva readily de- voured.
Wheeler arid Williams (1916) described the luminous or- gans in the New Zealand "glow worm9" Bolitophila Zumi- nosal as consisting of "the dilated tips of the four mal- pighian tubules which appear as four curved luminous rods and therefore constitute the photogenic organ.'' Hudson (1926) stated that the light emitted was brighter on warm damp nights and brightest immediately before daybreak. In Macrocera and Ceroplatus which I reared in my bed- room, I carefully looked for luminosity in the larval and pu- pal stages of these insects, for several nights? and in no case was it seen. It is probable that the luminosity in the Eur- opean Ceroplatus sesioides recorded by Wahlberg was due to phosphorescent bacteria as is the case in certain chirono- mus larvze.
'Dr. F. W. Edwards kindly sent me some larvae of the New Zea- land "glow worm." From the morphology of the larva, it is clear to me that the larva is related to the European Ceroplatus and not Bo- litophila* Hudson latm introduced the name Arachnocampa luminosa for the New Zealand "glow worm."




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19351 Immature Stages of Mucroceru a~glica 27 Food of Mucrocera
Most Mycetophilid larvze feed on fungus spores, hence their old name Fungivorid~. Some species are said to be carnivorous.
Norris, Wheeler and Williams attribute a carnivorous habit to the New Zealand "glow worm."
Hudson bred the larva in small tanks by feeding them with small flies which he regularly introduced. Thus, he said, "There was in fact practically nothing else in the tank which could have sustained the larva during the three and half months they have been in captivity and accounted for the speedy disappearance of the numerous flies so frequently introduced.''
Cheetham recorded a carnivorous habit for Polylepta lep- togaster and Hungerford stated that Sciara coprophila fed on the dead bodies of the adults of their kind. Mansbridge and Buston showed that the droplets of fluid in the webs of Platyura and Ceroplatus contain oxalic acid of sufficient strength to kill insects coming in contact with it. The excretion of oxalic acid by such larv~ is unexpected as it is by no means a product of larval metabolism. Such excretion is an aid to their carnivorous habit. I have examined by transparency several young Platyura, Macrocera and Ceroplatus and found their gut containing fungus spores. In two instances, I found the remains of some Collembola in the web of Macrocera, but such remains form a nice nidus for fungal growth. It is probable that these larva? may be partly carnivorous and partly fun- givorous.
The larva? of Polylepta leptogmter and Sciara cop~ophila are undoubtedly fungus eaters. It is evident that the carni- vorous habit in Mycetophilidze should be restricted to the web spinning species, namely the Ceroplatinze, Macrocerinze and Platyurinz.
Mo~phology
The mature larva (Fig. I, Pl. 4) is 20 mm. long and 1.5 mm. broad. The dorsal surface is convex and the ventral is flat. The larva is more like a small annelid worm or as Du- four said of the larva of Ceroplatus, "Elle est larve de dip-



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28 Psyche [March
the par sa partie anterieure et annelide par la reste du corps.'' The larva is yellowish in colour especially towards the posterior half. The anterior four and last body segments are moderately pigmented.
The integument is thin, polished and shining. The body
of the larva is free from hairs except for six groups of sen- sory hairs situated in the three thoracic segments in direct relationship of the imaginal buds of the legs. Each group consists of four hairs of equal length.
The body of the larva is composed of 12 body segments; the first four of which are smaller and quite distinct from the rest. They are rectangular in shape and the sides are produced into small sacs. The skin of the other body seg- ments is thrown into numerous transverse folds. Each fold is produced into a small sac at the sides. In preserved ma- terial, the last 8 body segments are difficult to make out on account of the transverse folds; thus in the closely related genus Ceroplatus, R6aumur thought the body segments were innumerable, while Husdon counted 19 body segments in the New Zealand "glow worn." The last body segment (fig. 8) is provided with two conical papilla? which are of variable size according to their state of turgescence. The head (Figs. 2, 3) is quadrate, dark brown and partly retractile in the first body segment. The frontal plate is egg-shaped with the pointed end situated on the posterior margin. The latter shows two deep lateral emarginations. The lateral epicranial plates curve towards the ventral sur- face of the head and meet anteriorly leaving a bell-shaped area covered with transparent chitin (Fig. 3). Anteriorly, each plate sends two tongue-shaped pieces of chitin which articulate with the condyles of the mandible. The antenna (an. Fig. 2) is convex and resembles a watch glass. It is supported by a strongly chitinised base and an annular band of chitin outside which four minute papilla? are present.
The eyes (E. Fig. 3) are small vestigial structures sit- uated postero-lateral to the antennz. Each consists of a transparent membrane overlying a layer of pigmented cells. The labrum (Fig. 4) is supported by a we11 developed chitinised frame which adjoins the frontal plate. The lat-



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19 3 5 I Immature Stages of Macrocera anglica 29 era1 ends of the frame articulate with two well developed arms (c.r.) which pass ventral to the labrum. Each arm is provided with a fan-shaped organ, . composed of several curved teeth, whose forward and backward movements help to direct the food particles towards the mouth opening. The labrum is a fleshy hood-like protuberance extending forward and downwards to recurve within the mouth. It is provided with 8 pairs of dorsal papillze.
The mandible (Fig. 5) is elongated and consists of a con- vex dorsal and a large flat ventral lamella. The dorsal la- mella is provided with one tooth and a well developed pro- stheca at the inner basal angle. On the medial border, the mandible carries three teeth and a small rounded tubercle. The muscles operating the mandible are well developed and consist of an abductor and an adductor muscle. The abductor muscle (ab. m. Fig. 5) takes it origin from the posterior and lateral side of the epicranial plate and consists of five bundles which converge towards the upper slender teniion which is inserted to the upper angle of the mandible. The adductor muscle (ad.m) arises partly from the lateral and partly from the ventral surface of the epicranial plate. The ventral and dorsal bundles converge towards the adduc- tor tendon to be inserted at the inner basal angle of the man- dible ventral to the prostheca.
The maxi112 lie ventral and parallel to the mandibles. Each maxilla (fig. 6) consists of two lobes. The inner lobe or maxilla proper is cultriform and carries seven teeth, the last of which is strongly chitinised and more rounded than the rest. The outer lobe is provided with an oval area an- teriorly, which is covered with a transparent membrane and bears one large circular and five small sensory papill~. The maxilla is produced posteriorly as a strongly chitinised rod which serves for the attachment of the adductor muscle. The two maxillze are supported along their posterior border by two triangular plates-the maxillary plates (mx- pl. Fig. 3) -which meet along the mid-ventral line.
The maxilla is provided with an adductor and an abduc- tor muscle. The first consists of several bundles which arise from the apex and lateral margin of the occipital foramen and are inserted to the rod-shaped process of the maxilla.



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30 Psyche [March
The adductor muscle takes its origin from the lateral side of the epicranial plate. It consists of several bundles which converge to a long slender tendon which is inserted to the outer basal angle of the maxilla.
The hypopharynx (Fig. 7) lies dorsal to the maxillae. It consists of two horizontal and two vertical processes. The free ends of the latter are seen between the inner borders of the maxillas (hy, Fig. 3).
Following them anteriorly,
they pass dorsal to the maxillae, slightly diverging one from the other and end by articulating with the horizontal proc- esses. The horizontal processes resemble chamois horns. They meet anteriorly at the mid-ventral line and support a semicircular membrane whose free border carries several sensory papillae (sp. Fig. 7).
The labium (lb. Fig. 7) is reduced to a small rectangular plate situated between the free ends of the vertical processes. The opening of the salivary duct lies dorsal to the labium. The alimentary canal consists of a short pharynx followed by a narrow tubular oesophagus which is invaginated in the proventricules. The mid-gut is in the form of a straight tube which gradually narrows down as it joins the hind-gut. The junction of the mid with the hind-gut is marked by four malpighian tubules which arise separately and extend forward, then backwards surrounding the hind-gut. From the anterior end of the mid-gut, two gastric caeca arise sep- arately and extend backward to the 6th body segment. In the living larva, the caeca exhibit strong peristaltic move- ments. The two salivary glands are in the form of two long narrow convoluted tubes which extend to the 8th body seg- ment. Anteriorly, they unite to form a common duct which opens between the distal ends of the vertical processes of the hypopharynx.
Respiratory System
The larvae of Macrocera,
Ceroplatus and Platyura are
apneustic. The tracheal system is well developed in Macro- cera, consisting of two latero-dorsal longitudinal trunks which extend from the first to the last body segment. The two trunks are connected together by 8 transverse branches situated at the end of the metathorax and the first seven



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19 3 5 I Immature Stages of Macrocera anglica 31 Psyche, 1935
VOL. 42, PLATE IV.
Madwar - Macrocera anglica.




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32 Psyche [March
abdominal segments. From each trunk, eight short lateral branches take their origin, which are connected to the skin of the prothorax and first seven abdominal segments by means of lateral cords which correspond to the position of the spiracles in other Mycetophilid larvae. Although functioning spiracles are absent in this larva, the conditions for cutaneous respiration are extremely favor- able1. The skin is thrown into numerous folds which in- crease the respiratory surface. The integument is thin and richly supplied with a subcuticular net of tracheoles. The larva lives under a hygroscopic web of salivary secretion. Description of Plate 4
Fig. 1
Fig. 2
Fig. 3
Fig. 4
Fig. 5
Fig. 6
Fig. 7
Fig. 8
Macrocera anqlica Edwards.
Whole larva taken out of web
Head - Dorsal aspect
Head - ventral aspect
Labrum - oral aspect
Mandible
Maxilla
Hypopharynx and Labium
Terminal body segment
Key to Lettering of Plate
An.
Ab.m.
Ad.m.
C.R.
E.
HY*
Lb.
Mx.
Mx.P.
Mx.Pl.
Pr.
S.P.
Antenna
Abductor muscle
Adductor muscle
Chitinous ring
Eye
Hypopharynx
Labium
Maxilla
Maxillary Palp
Maxillary Plate
Prostheca
Sensory Papilla
^he. modification of the respiratory system in some Dipterous larvae will be dealt with separately in a special paper.



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19351 Immature Stages of Macrocera anglica 33 Summary
1.
The Biology and Morphology of Macrocera anglica is given.
2.
Luminosity, development of carnivorous habits and the excretion of oxalic acid by the larva are discussed. 3.
The change from the peripneustic to the apneustic con- dition in the larva of Macrocera is accounted for. Acknowledgement
I wish to thank Prof. M. Khalil Bey, Director of the Re- search Institute, for his advice and helpful criticism. References
Cheetham, C. A.
1920 Polylepta leptogaster Winn. A Cave-dwelling Dipterous larva in Yorks.
Naturalist, vol. 45,
p. 189.
Dufour, L.
1839 Monographic du genre Ceroplatus. Ann. Soc. Nat. 2me. shrie, vol. XI, p. 193.
Edwards, F. W.
1924 British Fungus Gnats. Trans. Ent. Soc. London, 1924, pp. 505-670; Ann. Mag. Nat. Hist., 9th ser., vol. XIV, p. 175.
Enslin, E.
1906
Die Lebensweise der Larve von Macrocera fas- data Meig.
Zeits. Wiss. Insektbiol., vol. 2, pp.
251-253.
Hudson, G. V.
1926 Observations made on the New Zealand Glow- worm (Arachnocampa luminosa) During 1926. Ann. Mag. Nat. Hist., London, 9th ser., vol. XVIII, pp. 667-670.
Hungerford, H. B.
1916 Sciara maggots injurious to potted plants. Journ. Econ. Ent., vol. 9, pp. 538-549.
Madwar, S.
The Biology and Morphology of the Immature Stages of Mycetophilidae.
Philos. Trans. Royal
Soc. London (in press).




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34 Psyche [March
Malloch, J. R.
1917 Key to the Larvae of Diptera. Bull. Illinois Lab. Nat. Hist., No. 12, pp. 161-409.
Mansbridge, G. H.
1933 On the Biology of Some Ceroplatinse and Macro- cerinse. Trans. Ent. Soc. London, vol. LXXXI, pp. 75-92.
Norris, A.
1894
Observations on the New Zealand Glow-worm, Bo- litophila luminosa. Ent. Monthly Mag., vol. 30, pp. 202-203.
Rkaumur
1740
Mkmoires, vol. V, p. 23.
Schmitz, H.
1912 Polylepta leptogaster. Natuurhistorisch Genoot- schap, Limburg, Jaarboek, pp. 65-96.
Wheeler, W. M. and F. X. Williams.
1915
The Luminous Organ of the New Zealand Glow- worm. Psyche, vol. 22, No. 2, pp. 36-43.



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