We marked and numbered leaves with larval mines to observe their behaviour and development. In Assam, we followed 15 larvae and four successfully reached adulthood. In Kerala, about 20 larval and pupal mines were studied. Some specimens were taken to the lab to rear and collect certain life stages for vouchers, photography and measurements.

Figures 14–21. 

Natural history of Platypria (Platypria) hystrix on Pueraria phaseoloides, Kerala, India (Photos: K.D. Prathapan) 14 Vine growing over all plants in a banana plantation 15 Plant growing over banana 16 Inflorescence 17 Leaf with six larval mines, abaxial view 18 Leaf with six larval mines, adaxial view 19 Larval mine, view from adaxial side of the leaf 20 Larval mine, view from abaxial side of the leaf with ootheca at the centre 21 Pupal chamber.

In addition to the detailed study of P. (P.) hystrix above, HVG, PKD and SR observed and collected the other three Indian Platypria species on Ziziphus and other hosts in India and provide these brief notes below.

Natural history notes for Platypria (Platypria) echidna Guérin-Méneville, 1840 (Figs 26–28)

Authors HVG and SR observed live populations on four different hosts, all new records, in India. Locality 1: Pune District, Tamhini-Dongarwadi, Mulshi, 18°26'48.1488"N, 73°25'29.3808"E, June–September (monsoon season) 1997–2001. Locality 2: Pune, Paud Road, 18°30'24.066"N, 73°46'58.2708"E, 10 April 2011. These adults were noted feeding by scraping the upper leaf surface, Ziziphus rugosa Lam. Localities 3–4: Adults were observed feeding on Z. nummularia and on Z. mauritiana Lam. at Pune District, Bhimashankar, 19°4'36.1848"N, 73°32'6.8784"E, August 1999 and on Ziziphus xylopyrus (Retz.) Willd., Pashan, Pune, 18°32'12.1884"N, 73°47'22.6284"E, May 1999. Locality 5: Larvae, pupae, and adults together were observed only on Z. mauritiana, at Taljai Tekadi Pune, 18°31'13.548"N, 73°51'24.2784"E, September 2007.

Figures 22–28. 

22–25 Natural history of Platypria (Platypria) erinaceus on Ziziphus nummularia (Burm.f.) Wight & Arn., Maharashtra, India, (Photos: S. Ranade) 22 Ziziphus xylopyrus (with author HVG standing) 23 larval mines in small, rounded leaves of Ziziphus nummularia 24 larva 25 mature larva and pupa 26–28 Platypria (Platypria) echidna 26 Pupa, dorsal view 27 pupa, ventral view 28 adult, dorsal view. (Photos: H.V. Ghate).

Erythrina stricta (Fabaceae) was identified by A. K. Pradeep, Calicut University Herbarium, previously for Faizal et al. (2006). No plant voucher was collected at that time as no flowers were produced under Vellayani conditions; now the plant has become locally extinct. Pueraria phaseoloides was identified by A. P. Balan, Malabar Botanical Garden. Erythrina variegata, P. montana var. lobata and M. pruriens (all Fabaceae) from Assam were identified by G. Krishna, Central National Herbarium (CAL), Botanical Survey of India. The beetles were identified independently by authors KDP and SR as P. (P.) hystrix using the species key by Maulik (1919) and compared with photos of type specimens deposited in Berlin Museum of Natural History and Kiel University, Germany. A key to identify the four Platypria species in India is developed.

Specimens collected by KDP and associates over years from various localities in India are deposited in the Travancore Insect Collection, Kerala Agricultural University, Vellayani (KAU). In addition to KAU, specimens of beetles will be deposited also at the National Bureau of Agricultural Insect Resources, Bengaluru, India (NBAIR). Specimens of P. (P.) echidna and P. (P.) erinaceus are deposited at the Modern College of Arts, Science and Commerce, Pune, India. Additionally, a specimen series of P. (P.) hystrix is on loan from KDP to CSC for further study. Vouchers of P. phaseoloides (Accession no. 7019), P. montana var. lobata (Accession no. 7030, 7031) and M. pruriens (Accession no. 7037, 7038) are deposited in the Calicut University Herbarium, Department of Botany, University of Calicut, Kerala.

The four Fabaceae hosts are native to southeast Asia. Each is used for multiple purposes in agro-ecosystems. Erythrina stricta is a spinose tree on which cultivated black pepper (Piper nigrum L.) is trailed. It is also grown as a hedge plant and shade tree. Leaves are used as fodder for sheep and rabbit (Prathapan, personal observations; Sastri 1952). Erythrina variegata (Fig. 6) is a tropical soft-wood tree, closely resembling E. stricta; however, its stem is usually unarmed. It is cultivated as an avenue tree and a live fence and it is used as a shade tree in plantations of tea and coffee and to trail betel vine and black pepper (Sastri 1952; Prathapan, personal observations). Pueraria phaseoloides (Figs 14–18; tropical kudzu) is a perennial climbing vine, trailing over trees, shrubs, bananas and grasses in and around the Instructional Farm of Kerala Agricultural University, Vellayani, India. It is grown as a cover crop in rubber plantations and for fodder (see Keung 2002). Pueraria montana var. lobata, known for rapid and competitive growth, is used as a pasture, fodder and hay crop in North America (Lindgren et al. 2013). Mucuna pruriens is used for its medicinal properties and as fodder (Choudhary et al. 2012; Patiri and Borah 2007). These five hosts have moderately large, trifoliate leaves.

The genus Ziziphus Mill. includes about 58 species of spiny shrubs and trees (El Maaiden et al. 2020). It is extensively used in folk and traditional medicine in arid and semi-arid regions for the treatment of diarrhoea, dysentery, cholera, diabetes, hypertension, inflammation, intestinal spasm, liver, malaria and other diseases (El Maaiden et al. 2020). Ziziphus mauritiana Lam., called Indian jujube or ber, is a tropical shrub or small tree, of considerable commercial importance and is widely cultivated for its fruits. Ziziphus rugosa Lam., called wild jujube, is a thorny tree or straggling shrub, common in foothills and low mountains in India (Chadha 1976). Fruits are collected from the wild for consumption. Ziziphus xylopyrus (Retz.) Willd., locally called ‘kath ber’, is an erect shrub or small tree, common in dry and deciduous forests (Chadha 1976). Ziziphus nummularia (Burm.f.) Wight & Arn., occurring in semi-arid areas from Iran to the Indian subcontinent, is a multipurpose branched thorny shrub reaching a height of 1–3 m, with medicinal, nutritional, industrial and economic values (Zandifar et al. 2020).

Specimens were colour-photographed using a AF Micro Nikkor 60 mm macrolens, mounted on a Nikon D3000 SLR camera. The camera was mounted on a Wemacro stack rail, positioned vertically. Three Ikea 201.696.58 Jansjo Desk Work LED Lamps, with suitable diffusers, were used to uniformly illuminate the specimen. A Wemacro rail android Bluetooth control app, installed on a smartphone, was used to remotely control the imaging system. Multiple images at different depths of plane were taken and were stacked together using Helicon focus software. The high-resolution images, thus obtained, were edited with Adobe Photoshop 2020. Field photographs were taken using a Canon EFS 55–250 mm lens mounted on a Canon EOS 1300D SLR camera or Micro Nikkor 60 mm macrolens mounted on a Nikon D3000 SLR camera.

Life stages of P. (P.) hystrix were measured using a standardised ocular micrometer placed in one eyepiece of a stereoscopic microscope. Measurements of host plant leaves and leaf mines were taken using a Vernier caliper. In our Assam lab, we measured three adults, one instar I, one instar III, one instar V, one pupa and one pupal mine. In our Kerala lab, we measured 10 adults, 20 pupal mines, 10 pupae, and seven oothecae.

We use the current plant names according to the online catalogue (Tropicos 2020) and current beetle names according to the catalogue of Staines (2015).

We report Erythrina stricta, Pueraria montana var. lobata and Pueraria phaseoloides as new hosts for P. (P.) hystrix (Figs 6–21). In India, this beetle has been reported on other species in these genera, as well as on species of Cajanus, Desmodium and Dolichos (Table 1, all citations therein).

Starting on 17 September 2019, SR observed irregular blotch mining on leaves of a young tree of E. variegata (Fig. 9). Eggs were observed on E. variegata in Assam as well as on P. phaseoloides in Kerala. They were laid singly on the adaxial side of leaves. Up to four eggs were observed on a single leaflet. Individual eggs were inserted into a depression made on the mesophyll and were covered with a creamy-brown secretion to form the oblong-oval ootheca, that measured 1.03–1.32 mm (1.10 mm – mean of 7 observations) long and 1.07–1.48 times (1.24 times – mean of 7 observations) longer than wide. A characteristic, long, thread-like process, arising from the middle of the ootheca, enabled easy identification of the ootheca under low power of the microscope. From the abaxial side, the ootheca appeared like a minute, brown speck. The egg appeared soft and was easily ruptured when we attempted to separate it from the oothecal covering. The thread-like process and the outer wall of the ootheca remained intact even after hatching and formation of the leaf mine. In Assam, a female was observed on the host plant for ten days; oviposition and egg hatch were noted. Twenty-one leaflets were observed, each with about 3–4 beetle eggs. These eggs hatched in about 4–7 days. Many eggs remained unhatched or the larvae died prematurely.

The larva hatched out of the egg mines into the adjacent mesophyll without breaking the oothecal covering. It feeds and moves within the leaf creating mines by consuming mesophyll tissue. The first instar larva grew up to 1.8 mm. The larva has chitinous brown head and translucent-greenish body. The alimentary canal appears dark green due to the presence of food. While observing it against sunlight, the mines appeared occupied and small larvae were apparent through the epidermis. The larval mine in P. phaseoloides appeared less apparent in the abaxial view (Fig. 17), but clear and rather transparent from the adaxial side of the leaf lamina (Fig. 18). The larval mines are irregular blotch mines. Six leaf mines were observed on a 65 mm wide leaflet of P. phaseoloides (Figs 17–18) at Vellayani. The mines contained excreta, exuviae and often remnants of dead larvae. The leaf mines of the late instars were noticeable as some of them were approximately 1 cm wide and 10 cm long and irregularly shaped. The final instar was about 5 mm long.

Platypria is associated mainly with two plant families, Fabaceae and Rhamnaceae (Table 1). We found several citations in Indian literature about the genus that should be added to the online catalogue of Staines (2015). Records on other plants – Fagaceae [Nair (1986), Euphorbiaceae (Hua 2002) and Poaceae (Anand 1989; Maulik 1919, 1937)] – need confirmation as there is little information on immatures from these observations. We can call only those plants as ‘hosts’ where larval development occurs successfully. In that sense, P. (P.) echidna may sometimes feed on Z. nummularia, but we have never observed larvae or pupa of this species on Z. nummularia. Similarly, we never observed larvae/pupae of any Platypria species on Z. xylopyrus (Retz.) Willd. which we [HVG and SR] regularly visited to study bionomics of another cassidine. Further, although Z. oenoplia (L.) Mill. is reported as a host of one Platypria species (see Table 1), HVG never observed Z. oenoplia in Pune harbouring any Platypria.

Kalshoven (1957) noted that Platypria is one amongst a few unusual Oriental hispine genera associated with dicotyledonous plants, often belonging to different families. He also commented that Platypria is unusual as it is one of the few hispine taxa specific to dicots and exhibits trophic selections between unrelated host plant families.

Ayyar (1940) recorded P. (P.) hystrix as a leaf-feeding pest on Dolichos lablab, Sesbania sp. and Erythrina sp. in south India. He also noted P. (P.) echidna on Erythrina sp. in south India and P. (P.) erinaceus on Z. jujuba. Nair (1986) recorded P. (P.) erinaceus as a pest on Z. jujuba, as well as P. (P.) hystrix on D. lablab, Sesbania sp. and Castanea sp. (Fagaceae, chestnut) in India. Rani and Sridhar (2004) recorded P. (P.) hystrix as a pest damaging leaves of Mucuna pruriens L. (DC) var. utilis in south India (this plant is used as a nerve tonic and aphrodisiac in Indian traditional medicine). However, P. (P.) melli is known as a significant pest of Rhamnaceae fruit trees, Hovenia acerba and Ziziphus jujuba, in China (Liu et al. 2019). In India, there have been no reports of outbreaks or severe crop damage.

All life stages of P. (P.) hystrix (egg to adults) were observed in both south and northeast India. The natural history of the populations observed in Assam, northeast India and in Kerala, south India were rather identical, irrespective of the host species, though the populations are separated by a distance of > 2,500 km and climates are distinct. The south Indian population at Vellayani was active throughout the year as harsh winter or summer is absent here, while the northeast Indian population vanished as the winter peaked and re-appeared only after receipt of rains in summer, thus disappearing for at least three months from December to March.

Information is limited on the eggs and associated maternal behaviour for leaf-mining hispines. In P. (P.) hystrix, we observed females excavating a depression on the abaxial surface of leaves and laying a single egg there. Then she covered the egg with a yellow secretion that turned red brown on drying and formed a crusty oothecal covering. Thrusting single eggs into the leaf lamina is known in some leaf-mining hispines (Chen 1982; Chaboo et al. 2010; Shameem et al. 2016; Liao et al. 2018b), although Taylor (1937) noted that females of Promecotheca species may oviposit on the leaf surface or sink the egg into the leaf and the natal larva starts the mine. In Prionispa champaka Maulik, 1919 (Oncocephalini), the female oviposits 5–6 eggs into a channel she cuts on the leaf (Liao et al. 2018a). Chaboo (2007: 244) proposed two egg features (egg stalk and faecal cover) for phylogeny reconstruction; our data here suggest at least three new potential character hypotheses about the oviposition site (externally on leaf surface or thrust into the leaf tissue), egg grouping (single or massed) and maternal covering (naked with no covering, oothecal secretion, faecal/plant covering or oothecal secretion + faecal/plant covering). Verma and Kalaichelvan (2004) reported observations on oothecal structures in Indian Cassidinae; however, our observations of such secretions in Platypria indicate the behaviour of maternal coverings is more widespread across the cassidine tree of life. It is very important to document such information in fine detail to achieve better resolved phylogenies of Cassidinae s. l.

We observed all larvae of the four Indian species of Platypria making a blotch mine, as in some other mining Cassidinae (Bernon and Graves 1979; Chen 1982; Lee et al. 2009; Liao et al. 2014, 2018a). Figs 17–18 show six mines in one leaf; however, we are uncertain how many larvae can be sustained by the single leaflet to reach pupation and adulthood. We observed a single larva per mine, agreeing with observations in Javeta pallida Baly, 1858 (Shameem et al. 2016) and Chaeridiona thailandica Kimoto, 1998 (Świętojańska and Kovac 2007). This contrasts with those mining species whose larvae live gregariously in a common mine (e.g. Pr. champaka, Liao et al. 2018a).

In our Platypria species, the mature larva exits the larval mine and constructs a separate leaf mine for pupation (Figs 12, 13 and 21; see Suppl. material 1 on Pensoft’s Youtube channel: https://www.youtube.com/channel/UC3mfJg-mxTVrXOjE3XrkAMw). This is different from P. (P.) melli Uhmann, 1954 (Liao et al. 2014) where the larva mines into the mid-rib to pupate; such a mid-rib pupation mine is also known in C. thailandica (Oncocephalini; Świętojańska and Kovac 2007). The behaviour of a different pupation mine within the leaf blade is also known in some mining cassidines – Cassidispa relicta Medvedev, 1957 (Hispini; Liao et al. 2018b), Oncocephala promontorii Péringuey, 1898 (Oncocephalini; Chaboo et al. 2010), Notosacantha vicaria (Spaeth, 1913) (Notosacanthini; Rane et al. 2000) and Pr. champaka (Liao et al. 2018a). In contrast, other leaf-mining cassidines pupate within the larval mine. Species of Dactylispa Weise (Hispini), which feed on either monocots or dicots, pupate within the larval leaf mine (Zaitsev 2012). The rice pest, Dicladispa armigera (Olivier, 1808) (Hispini) and the palm-feeder, Javeta pallida (Shameem et al. 2016), both have pupation within the larval mine.

The structure of the pupal mine appeared very similar in our observed Platypria species. In C. thailandica (Oncocephalini), the mature larva exits the larval mine, bores into the mid-rib forming a pupal chamber and then pupates with the head orientated towards the stem of the plant (Świętojańska and Kovac 2007). Members of Hispini, Notosacanthini and Oncocephalini, that live on eudicots, create more or less similar pupal mines.

Chaboo (2007: 244) proposed Character 18 with four states for different pupation sites across Cassidinae s. l. Our new observations here suggest that the origin of the pupation mine can provide an additional character hypothesis with two states – within a larval mine or a separate mine.

The pupal mines of P. (P.) hystrix are U-shaped and the resident pupa is positioned such that its rear end is orientated to the single opening at the wider end. This facilitates respiration with the erect, tubular spiracles. Even in rains when the pupal mine may become flooded, the pupa can be seen projecting spiracles out of the opening; the pupa is motile and not glued like other Cassidinae. Similar pupal mines have been reported for P. (P.) echidna and P. (P.) erinaceus and some other basal Cassidinae, such as Chaeridiona picea Baly (personal observations SR; Oncocephalini), Notoscantha (Rane et al. 2000; Notosacanthini), and Oncocephala tuberculata Olivier,1792 (Oncocephalini). Notosacanthini is one of the historic transitional tribes between crown-clade Cassidinae, based on adult morphology and basal “hispines” (Chaboo 2007). The similarity of its pupal chamber to that of Platypria and Oncocephalini underscores the need for re-assessment of its taxonomic placement.

Chatterjee and Bhasin (1936) and Kalshoven (1957) reported Platypria adults as exhibiting swarming behaviour on Rubus ellipticus Sm. (Rosaceae) in India. We did not observe such behaviour. Swarming has been reported for only one other Cassidinae, Caelaenomenodera elaeidis Maulik (Bernon and Graves 1979), where this behaviour appears to be cyclical. It could provide another set of phylogenetically informative characters.

Platypria females attract many males in a mating frenzy. Once a male is chosen, copulation lasts several hours. (See our supplementary movie file on the life cycle of Platypria in India).